Are All Calories the Same?

As you and millions of other people embark on new dietary journeys, you’re going to hear a ton about calories.

“Calorie counting is everything.”

“If you aren’t counting calories, you won’t lose weight.”

“Just eat less calories than you expend.” For one, it’s “fewer.” Two, that’s not the whole picture.

These statements aren’t wrong exactly, but they offer an overly simplistic picture of the relationship between weight loss and calories. They ignore context. And context is everything, especially when you’re talking about calories and weight loss.

Most people (even many scientists) believe that the body composition challenge is a relatively simple equation: to lose weight you must reduce calories (either eat less or burn more), to gain weight you must add calories (eat more or burn less), and to maintain weight you keep calories constant (eat and burn identical amounts). Calories in over calories out.

Right away, it sounds preposterous. Are people really maintaining perfect caloric balance by dutifully tracking and comparing their intake to their burn? Are they walking six fewer steps lest they lose an extra ounce off their midsection?

Are All Calories the Same?

The truth is, it’s more like a complex equation where you have to factor in many other very important variables:

  • Am I getting calories from fat, protein, or carbs?
  • Am I getting my calories through whole foods or refined processed foods?
  • Are my glycogen stores full or empty?
  • When’s the last time I exercised?
  • Am I insulin-sensitive or insulin-resistant?
  • Am I trying to lose “weight” or lose fat?
  • How’s my stress level?
  • Am I sleeping enough?

The answers to all those questions (and more) affect the fate of the calories we consume. They change the context of calories.

Ideally, all that complexity is handled under the hood. That’s how it works in wild animals. They don’t calorie count. They don’t think about what to eat or how to exercise. They just eat, move, sleep, and somehow it all works. I mean, they die, often violently, but you don’t see obese, metabolically-deranged wildlife—unless the obesity and metabolic derangement is physiological, as in bears preparing to hibernate. Somehow they figure it out. They’ve delegated the complex stuff to their subconscious.

This is generally true in “wild humans,” too. Hunter-gatherer groups by and large did not and do not show any evidence of metabolic derangement, obesity, or the other degenerative trappings of modern humans living in civilization. They are fully human in terms of physiology, so it’s not that they have special genetic adaptations that resist obesity. They’re living lifestyles and eating diets more in line with our evolutionary heritage. They’re moving around all the time, not going through drive throughs. They’re eating whole unprocessed foods that they have to procure, catch or kill.

What they don’t have is the ridiculous concept of calories and macronutrients floating around in their heads, informing their dietary choices. They don’t even think about food in terms of calories, or movement in terms of calories expended. Metabolically speaking, they consume their calories in the proper context.

But you? You might have to think about context. You might have to answer those questions and create the proper context.

Most people do not think about context. They home in on the number of calories the food database claims the food they’re eating contains, plot it against the numbers of calories the exercise database claims the exercise they’re doing expends, and then wonder why nothing’s working. That’s why “dieting doesn’t work”—because, as practiced in accordance with the expert advice from up high, it doesn’t. Almost invariably, the people who see great results from strict calorie counting, weighing and balancing, those types who frequent online weight lifting forums and have the freedom to spend hours perfecting their program, have the other relevant variables under control without realizing it.

They’re younger, with fewer responsibilities—and less stress and fewer disruptions to their sleep.

They’re lifting weights and training religiously, creating huge glycogen sinks and maintaining optimal insulin sensitivity.

They’re eating a lot of protein, the macronutrient that curbs hunger and increases energy expenditure the most.

They’re eating mostly whole foods.

They’ve had less time on this earth to accumulate metabolic damage.

Not everyone is so lucky.

Fat burning, glucose burning, ketone burning, glycogen storage, fat storage, gluconeogenesis, and protein turnover—what we do with the calories we consume—do not occur at constant rates. They ebb and flow, wax and wane in response to your micronutrient intake, macronutrient intake, energy intake, exercise and activity habits, sleep schedule, stress levels, and a dozen other factors. All of these energy-related processes are going on simultaneously in each of us at all times. But the rate at which each of these processes happens is different in each of us and they can increase or decrease depending on the context of our present circumstances and our long term goals. All of these processes utilize the same gene-based principles of energy metabolism—the biochemical machinery that we all share—but because they all involve different starting points and different inputs as well as different goals or possible outcomes, they often require different action plans. We can alter the rate at which each of these metabolic processes happens simply by changing what and when we eat and addressing the non-dietary variables. We can change the context.

But don’t controlled trials demonstrate that a “calorie is a calorie”?

People hear things like “in controlled isocaloric trials, low-carb diets have never been shown to confer a metabolic advantage or result in more weight loss than low-fat diets.” While often true, they miss the point.

People aren’t living in metabolic wards with white lab coats providing and precisely measuring all their food. They’re living in the real world, fixing their own food. Free living is entirely uncontrolled with dozens of variables bleeding in from all angles. In the lab situation, you eat what they give you, and that’s that. The situations are not analogous—real world vs. controlled lab environment.

In real world situations…

Why a Calorie Isn’t Just a Calorie

The macronutrient composition of the calories we eat alters their metabolic effects.

The metabolism of protein famously increases energy expenditure over and above the metabolism of fat or carbohydrate. For a given caloric load, protein will make you burn more energy than other macronutrients.

Protein is also more satiating than other macronutrients. Eat more protein, curb hunger, inadvertently eat less without even trying (or needing a lab coat to limit your intake).

Protein and fat together (AKA “meat”) appear to be even more satiating than either alone, almost as if we’re meant to consume fat and protein in the same meal.

The isocaloric studies tend to focus on “weight loss” and discount “fat loss.” We don’t want to lose weight. We want to lose fat and gain or retain lean muscle mass. A standard low calorie diet might cause the same amount of weight loss as a low-carb, high-fat diet (if you force the subjects to maintain isocaloric parity), but the low-carb approach has been shown to increase fat loss and enhance muscle gain. Most people who lose weight with a standard approach end up losing a significant amount of muscle along with it. Most who lose weight with a low-carb, higher-protein-and-fat approach lose mostly fat and gain or retain most of their muscle.

Take the 2004 study that placed overweight men and women on one of two diets: a very low-carb ketogenic diet or a low-fat diet. The low-carb group ate more calories but lost more weight and more body fat, especially dangerous abdominal fat.

Or the study from 1989 that placed healthy adult men on high-carb or high-fat diets. Even though the high-carb group lost slightly more body weight, the high-fat group lost slightly more body fat and retained more lean mass.

Both describe “weight lost,” but which is healthier?

Whether the calories come in the form of processed or whole food determines their effect.

We even have a study that directly examines this. For two weeks, participants either supplemented their diets with isocaloric amounts of candy (mostly sugar) or roasted peanuts (mostly fat and protein). This was added to their regular diet. After two weeks, researchers found that body weight, waist circumference, LDL, and ApoB (a rough measure of LDL particle number) were highest in the candy group, indicating increased fat mass and worsening metabolic health. In the peanut group, basal metabolic rate shot up and neither body weight nor waist size saw any significant increases.

Your current metabolic state determines the effect of calories.

In one study, a person’s metabolic reaction to high-carb or low-carb diets was determined by their degree of insulin resistance. The more insulin resistant a subject, the better they did and the more weight they lost on low-carb. The more insulin sensitive a subject, the better they did and the more weight they lost on low-fat. Calories were the same across the board.

In another study, insulin-sensitive obese patients (a rarity in the general population) were able to lose weight on either low-carb or low-fat, but insulin-resistant obese patients (very common) only lost weight on low-carb.

Whether you exercise determines the effect of calories.

If you’ve just finished a heavy lifting workout followed by a sprint session, your response to a given number of calories will differ from the person who hasn’t trained in a year.

Training: Your muscle glycogen stores will be empty, so the carbs you eat will go toward glycogen storage or directly burned, rather than inhibit fat burning. Your insulin sensitivity will be elevated, so you can move protein and carbs around without spiking insulin and inhibiting fat release. You’ll be in hypertrophy mode, so some of the protein you eat will go toward building muscle, not burned for energy.

Not Training: Your muscle glycogen stores will be full, so any carbs you eat will inhibit fat burning and be more likely to promote fat storage. Your insulin sensitivity will be low, so you’ll have to release more insulin to handle the carbs, thereby inhibiting fat burning the process. You won’t have sent any hypertrophy signals to your muscles, so the protein you eat will be wasted or burned for energy.

How you slept last night determines the effects of calories.

A single night of bad sleep is enough to:

  • Give you the insulin resistance levels of a diabetic. Try eating carbs in an insulin-resistant state and tell me a “calorie is a calorie.”
  • Make the reward system of your brain light up in response to junk food and dampen in response to healthy whole food. The more rewarding you find junk food, the more your brain will compel you to eat more of it.
  • Reduce energy expenditure. Your “calories out” drops if you sleep poorly.

And those are just a few important variables that determine the context of calories. There are many more, but this post has gone on long enough…

The Take-Home Message

If calorie-counting works for you, great! You’re one of the lucky ones. Own that and keep doing what you’re doing. You’ve clearly got a good handle on the context of calories.

If calorie-counting and weighing and measuring failed you in the past, you’re not alone and there’s a way forward. Address the variables mentioned in this post that need addressing. Do you need better sleep? Do you need to manage stress better? Could you eat more protein or fat, eat more whole food and less processed food, or get more exercise, or lift more weights, or take more walks?

Handle those variables, fix those deficiencies, and I bet that your caloric context will start making more sense. The trick isn’t to increase the number of variables you plug into your calories in/calories out formula. It’s to make sure all your lifestyle and dietary ducks are in a row so that the caloric balance works itself out.

By understanding how these metabolic processes work, and knowing that we can control the rates at which each one happens through our diet (and exercise and other lifestyle factors) we needn’t agonize over the day-to-day calorie counting. As long as we are generally eating a PB-style plan and providing the right context, our bodies will ease into a healthy, fit, long-lived comfort zone rather effortlessly.

So, what’s your caloric context looking like? Thanks for reading today, everyone.


Pontzer H, Wood BM, Raichlen DA. Hunter-gatherers as models in public health. Obes Rev. 2018;19 Suppl 1:24-35.

Claesson AL, Holm G, Ernersson A, Lindström T, Nystrom FH. Two weeks of overfeeding with candy, but not peanuts, increases insulin levels and body weight. Scand J Clin Lab Invest. 2009;69(5):598-605.

Volek J, Sharman M, Gómez A, et al. Comparison of energy-restricted very low-carbohydrate and low-fat diets on weight loss and body composition in overweight men and women. Nutr Metab (Lond). 2004;1(1):13.

Mccargar LJ, Clandinin MT, Belcastro AN, Walker K. Dietary carbohydrate-to-fat ratio: influence on whole-body nitrogen retention, substrate utilization, and hormone response in healthy male subjects. Am J Clin Nutr. 1989;49(6):1169-78.

Cornier MA, Donahoo WT, Pereira R, et al. Insulin sensitivity determines the effectiveness of dietary macronutrient composition on weight loss in obese women. Obes Res. 2005;13(4):703-9.

Ebbeling CB, Leidig MM, Feldman HA, Lovesky MM, Ludwig DS. Effects of a low-glycemic load vs low-fat diet in obese young adults: a randomized trial. JAMA. 2007;297(19):2092-102.

Benedict C, Hallschmid M, Lassen A, et al. Acute sleep deprivation reduces energy expenditure in healthy men. Am J Clin Nutr. 2011;93(6):1229-36.

***This article was substantially revised from the original version, which you can read here.

TAGS:  calories, Keto

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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106 thoughts on “Are All Calories the Same?”

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  1. Great post, guys. I have long thought that the “black box” theory of calories in, calories out doesn’t make much sense in the real world. I always tried to put it in environment context though. I’d never really thought about the metabolic context. I feel much educated. What’s my takeaway message? The thing that I have learned most from you guys over the past year: you should tailor your food not just to your goals but to your activities as well. It sounds so simple when I type it out like that but for me it was a revelation. Thanks!

  2. Really great post. It all depends what you want and its so important to be keeping healthy and making the good choices- and to figure out what kind of fuel our bodies need for what we require of them.

  3. I just started using the food log on, as suggested by Mark a few months ago. I believe I am pretty active and eat well, well, not according to you all, as I do eat some carbs. It has been an eye opener to see what the breakdown of my diet really is. I’m happy to say that I’m usually pretty well covered nutritionally, but i want to take off the ten pounds I put on accidentally.

    So, Mark, what percentage of one’s diet should be appropriated to proteins, fats, and carbohydrates?

    BTW, I find the info fitday fascinating and it has been keeping me more attentive to the quality of my meals. I do wish they listed in line skating as one of their activities though! It’s one of my staples.


  4. Pat,

    The point I was trying to make here is that there is no set percentage formula. It all depends on your “context” and what you are trying to achieve. It’s almost never about percentages of Fat/Pro/Cho, but rather figuring your exact “average” requirements of each individual nutrient. It’s different for everyone. I guess I’ll do a follow-up post to go into the “math” of figuring out your daily needs with some examples.

    1. Hi Mark, I love what you’re doing to help us all here!!
      I do have a question about this as well, I’m looking back to see where I was loosing weight and what %’s I was taking in, would that be the recommended way to determine what my requirements are to loose weight?
      The last couple weeks I haven’t budged but weight wise, although I feel it, but wondering if this is how I can hone into how my body reacts to what I’m taking in…..
      I’m looking all around the site and dont see where you might have posted on the math…

      thank you!!

    2. As much as people from all dietary backgrounds love to riff on Atkins, that’s actually a good start. If you have body fat to lose, start at 20g of carbs a day, then up your intake by about 5 or 10g a week. (If you’re really carb-sensitive, better make it 5.) The Eadeses in their book Protein Power also give a method of calculating lean mass so you can figure out your protein needs (they also factor in activity level). It’s a starting point from which to experiment, anyway.

  5. I do 65% fat 30% protien and 5% carbs just because i want to lose weight as fast as i can.

  6. I wrote Mark awhile back and as part of that exchange I identified my carb intake as being 60-80 grams a day. I thought I was closer to 60 most days than 80s. Well here’s the numbers over the last couple of weeks according to Fitday:

    Average Calories
    grams cals %total
    Total: 1674
    Fat: 92 831 50%
    Sat: 29 262 16%
    Poly: 15 136 8%
    Mono: 31 278 17%
    Carbs: 95 345 21%
    Fiber: 8 0 0%
    Protein: 95 380 23%
    Alcohol: 15 106 6%

    If you told me that I would average 1674 calories, I would think that I’d be dropping weight pretty fast. But it’s coming off slow at this point, and that carb count probably has a lot to do with that.

    I didn’t jump on the Challenge because I thought I was already living by the BP. But I’m eating a lot more fruit than Grok probably did.

  7. Dave, you’re trying to burn fat but eating 831 calories of fat a day. You want to see why you are not losing fat faster, look at that.

    1. I think you need to read Mark’s post again, Joe.

      Although if he’s above his carb tolerance at 90+ grams a day, and has his insulin up as a result, of course the dietary fat will be stored. But if he gets his carbs lower that won’t necessarily be true.

  8. Joe,
    I’m not sure that is necessarily true.
    You need to get your calories from somewhere.
    According to the PB, Grok’s diet consisted mostly of fat and protein. If Dave cuts out all those healthy fat calories, how will he replace them?
    I wouldn’t mind hearing what Mark S. has to say about it.


  9. you’re trying to burn fat but eating 831 calories of fat a day. You want to see why you are not losing fat faster, look at that.

    That flies in the face of everything I’ve come to believe over the last year of reading this blog, several others, and Gary Taubes’ book. One of the mantras I’ve repeated in discussing diet in other forums is that “eating fat doesn’t make you fat.” My fat consumption has stayed pretty constant over the last 11 months, including a three month period where I dropped 30 pounds. I’m still losing but it’s been a bit of a roller coaster in that after steady losses, I’ll have a spike where I put back three or four pounds. Those spikes correlate directly with carb binging. Case in point: I stepped on the scale on the morning of July 3rd and weighed 199. That’s the first time I’ve been under 200 in maybe 17 years! I was going to post a “breaking the Mendoza line” entry on my blog but I decided to hold off. Good thing. On the 4th of July I chased my grilled t-bone with five pieces of pistachio creme pie and four bottles of Shiner Bock. I was afraid to get on the scale Saturday but I finally did on Sunday and it read 205! It seems I pay dearly for carb binging (my attempts to find an oral surgeon who does sweet tooth extractions has been futile). I have cut back on fats somewhat recently but only because of the calorie content it was adding. I used to bathe my salads in olive oil and vinegar dressing, and I ate a lot of almonds. When I first started using Fitday was the first time I realized how calorie dense that dressing was. So now I only use a couple of tablespoons and I don’t munch on almonds.

    My plan going forward now is to cut back a little on the fruit, especially the tropical stuff that I love (mango & pineapple). I’m still going to have my daily apple (to not do so sounds sacrilegious). As long as I avoid the binging, the weight will come off. I’m just a little surprised that my total calorie intake is as low as it is. It’s probably a testament to the satisfying nature of good fats that I can eat this way and not feel hungry!

    1. Oooo! Pistachio cream pie!!! That would break me, too!! I hope it was really, really good pie! But yeah, 5 slices of something like that will truly wreak havoc in your system. I am weak that way, too. I had a rough couple of weeks at work, and used chocolate to stay awake for late hours. 5 lbs later…

  10. Eating fat dosn”t make you fat,but if you eat to many carbs with that fat it will.I tried adding in berries iam to carb sensitive,i stick with fat mostly saturated,meat,and a little veggies.As soon as i cut the beer out i started lossing again.

  11. Guys, don’t forget that the scale isn’t the best thing to look at sometimes. Depending on your hydration levels and whether you’ve excreted your bowels that day, I’d give or take 5 lbs.

    Overnight, I lose around 5 lbs, after I wake up and pee.

    I’d say go for bodyfat % measurements to see how much leaner you are.

    And a mirror doesn’t lie, as long as your brain is willing to not lie to you about how you feel about yourself!

    1. Getting bodyfat measurements can be weird if you don’t have access to the accurate methods for whatever reason. Might be better just to measure waist and hips and thighs and upper arms once a week or once a month. The scale can at least demonstrate a trend but I tend to weigh once a week, not once a day.

    2. Very very true.. I had dropped weight to 125 from 142 and was at 23.6% bf then noticed a big change in my body, I went up to 129-130 depending on the time of day lol, and my bf dropped to 20.6.

      I cut the carbs out entirely went through the candida die off phase and about two months in I am loving it all. My cloths fit better and I don’t mind the 5lb weight gain of muscle, because I am LOVING that 20.6% Scale numbers can be dangerous if you don’t consider your bf%…. 🙂

  12. Arthur: Yep, that’s true. That’s why I gave up my weekly “Tale of the Scale” on my blog. If it just happened I was a little “backed up” on Fridays, then it looked like I wasn’t making any progress. But I assure you that I’ve had enough “carb events” to be convinced there is a correlation that goes beyond a liquid/waste variance.

  13. Perfect discussion to reflect upon the post. When Dave (or anyone) has a great couple of days or weeks of low carb eating, the body gets into a fat-burning mode. Doesn’t matter that he gets 831 calories from fat because he does need a minimum number of calories to cover his daily needs and it has to come from somewhere if not from carbs (or else he would burn muscle off as well as fat). As long as his daily protein is high enough to repair and build muscle and a little extra to offer up as glucose through gluconeogenesis, everything is working according to his plan. Where the plan changes (OK, the context changes), is when he adds the 5 (count’em, 5) pieces of pie. With the insulin spike here, most of what he eats will try to get stored: sugar as glycogen first, then fat; fat as adipose fat; aminos from the steak as muscle first, then glucose, then fat.

    I suspect that some of the overnight weight gain is muscle glycogen, which carries an extra 4 grams of water weight with each gram of glycogen. In this one evening’s indiscretion, not much damage is done in the way of excess fat storage. Some, but not so much that getting back on the program the next day can’t start to reverse it again. Furthermore, if Dave were to decide to do a longer, harder workout the next day, he could deplete the glycogen (and water with it) and find that he’s pretty much right back to normal weight. No harm from that minor foul. That’s why it’s not cool to beat yourself up after a bad day or two. As long as you get back on track and stay PB 80% (or more) of the time, you’ll move towards your ideal genetic expression, which is lower body fat, higher muscle/power, etc. Of course, if you live PB most or all the time, you’ll get there a little sooner and be able to maintain it easier.

  14. I’ve known for a long time that a 100 calorie piece of candy is processed differently than a 100 calorie apple.

    But it’s only within the past few months that I figured out (largely with the info from Mark’s Daily Apple) that grains have a huge effect on my body composition. When I knock off the grains for a week, I’m visibly leaner and harder. A couple days back on the grains and boom!, I’ll start looking and feeling squishy around the middle. I believe it goes beyond the water retention that comes with carbs.

    On the other hand, my body really responds well to fruit. I can eat massive quantities of fruit (watermelon! plums! strawberries!) and it revs me up like a hummingbird so that I burn off the extra calories it provides. One of those individual differences that I had to figure out by paying attention.

  15. Informative and helpful post (and comments). Thanks!
    I haven’t figured myself out quite yet (you’d think by now…). It’s part of my 30 day challenge to do that (or at least start paying a little more attention). I plan and plan, but don’t always follow-up with a little day-to-day observation.

  16. Well, then, I guess I’m a failure:(

    I’m pretty well finished eating for the day here on the East Coast and my breakdown is as follows:

    1509 Calories
    61 Grams Fat (little Saturated)
    140 Grams Carbs (whoops, but mostly fruit and veggies
    108 Protein

    I move around on a daily basis, skating, biking, walking rounds of golf and lift weights twice a week.

    Just excluding alcohol and sweets from my diet has made my clothing looser in a few days.

    I am sucked into watching fluctuating numbers on the scale.

    BTW, I’m 5′ 4″ and weigh 134, but my Body Fat is higher than it should be, while still within “healthy” numbers. Unfortunately, I am fighting the menopause pudge at 56.

    To commit to excluding grains would be tough.

    1. Pat, when I started excluding grains I started with one at a time. That might help. My first one to go was wheat because it gave me the most grief, but little by little your body will kind of say “oh no your didn’t” when you eat something that is not good for you. However, you have to be pretty clean for a while to “hear” your body. Menopause pudge is rough. I’m 64 and have been trying to keep my stress levels down, stress is BAD for sleep and good eating. Sigh.

  17. Pat,

    Trust me, excluding grains isn’t too tough. Once you get past the three weeks phase of excluding them, you don’t crave them anymore. Keep your resolve high! You can do it.

  18. Pat, slice off some of those carbs (dare I say atleast half of them) and I think you weight will start going downwards.

  19. Good stuff. From a diabetic perspective I found this paper covers much of 21st century dietary theory

    more excellent stuff on that site.

    I don’t have to bother with weight reduction as I’m generally a skinny bastard anyway, the only thing that made me put on weight was the Healthy High Carb Low Fat diet and IMO it’s a toss up between the high carbs and the low fat as to which had most effect in worsening my BG and lipids. There’s no doubt in my mind that metabolism is several orders of magnitude more complicated than the soundbytes you get fed over the media, and all too many “medical professional” sites, certainly with my family’s genes Taubes & co. are right

  20. So, not sure if this discussion is still active, but I’m curious: do I count calories overall or not? And further, is it possible too have too few calories?

    I’ve been doing PB for a while, segued into it from more general low-carb. I turn those ketostix a lovely shade of purple, but just don’t seem to be losing any weight. I’m working out (turbulence training), and I track everything I put in my mouth. Keep calories to about 1800 or so a day. Help!

    1. 1800 calories is semi-starvation, if I’m not mistaken. Fitday tracks micronutrients as well as macro and calories… make sure you’re getting what you need. I was reading over at WholeHealthSource that merely supplementing with a multivitamin encouraged weight loss in obese people. I suspect what people think of as “starvation mode” on very low calorie diets is actually malnutrition that shuts down metabolism. I mean, from what I can tell, *ketosis* is starvation mode, and most people lose weight with that if everything else is working properly.

  21. If you truly eat “Primally” there’s no need to count calories. But I ‘d need more info, like where are you at in weight and body fat? where do you want to be? are you sprinting ever? etc.

  22. I’m hovering around 200. 42 years old, 5’9″, probably around 17 or 18% bodyfat.

    I do HIIT 3-4 times a week on an eliptical trainer. Bad feet, so running/sprints not really an option.

    Not sure if it’s the fish oil, PB, vitamin D or what, but I feel great. I really even notice a lot of mental fog has disappeared (didn’t even know it was there until it was gone), but the fat loss just doesn’t seem to be happening. Could I actually need to bump UP calories?

    I’ve even been doing a fast once a week, thinking of going to two. The first few weren’t fun, but after a few under my belt, it’s not so bad.

  23. I wouldn’t bump the calories up. Just keep doing what you’re doing and IF once or twice a week. May take a while to draw down your extra fat stores

  24. Mark,
    I hate to be so picky, but just wanted to point out that Carbohydrates are used structurally. Many post-translational proteins and membrane lipids are glycosylated in order to become biologically active. And what about the extremely prevalent carbohydrate ribose? It is found in every cell as a component of RNA, DNA, ATP, etc! The point being, the food we eat, even carbohydrates, are much more than just sources of energy. And, I agree with you, we are fools to think that we can over simplify such a complex phenomenon such as cellular biochemistry to help us lose a few pounds. It is not as simple as Calories in vs Calories out.

    1. Your body can make sugar, though. So there’s no need to eat the stuff in order to have sugars to use structurally. In fact it can be dangerous, because it doesn’t take much to go over your structural requirement for ribose or whatever, and then you wind up with all that surplus glucose that your body has to get rid of *right now.* This, by the way, is why glucose has been termed the body’s preferred fuel. It is not because your body sits around going, “Gee, I believe I would like some sugar right now.” It’s because when that glucose hits your system, your body goes “OMG! INCOMING! QUICK, GET RID OF IT!”

      As I pointed out somewhere else recently, alcohol is an even more preferred fuel than glucose. Again, not because the body’s sitting around going “Gee, I would really like a six-pack of Bud today,” but because it’s poison. I think it’s rather clever of Nature, actually, to arrange matters such that our bodies can sometimes get rid of toxic substances by turning them into fuel.

  25. Hi Guys, appreciate any advice people can offer…Im 5’8, 143 pounds (about 120 pounds lean BW). I train 4-5 times a week, mostly following crossfit workouts. I’ve been working on my food log, but somedays the calories Im consuming seem low around 1800, with the highest day around 2350. Do I need to be consuming more food if I want to increase my muscle mass? My protein intake is already over the suggested 1 pound per pound lean BW, and my fat intake is around 50% of my calories, and my carbs are around 110g a day. So do I need anymore calories to add some muscle mass? and if so where should I be getting then from?
    Sorry for the long post! Thanks for the help

  26. How much is 100-150 grams of carbs I am realy confussed. How do I know how many calories I should eat in a day, I want to loose 10 pounds, I am 130lbs now (female) I workout lots weights and cardio, people say I look good. I just have a goal that I want to get to and 10 pounds good on my legs arms and butt. I have tried everything my weight does not want to budge. I am really frustrated please help, I am reading the primal blueprints book but getting more frustrated and confussed. Please Help!

    1. These are all from

      3 cups cooked, instant oatmeal = 128g of carbohydrate.

      2 large, white baked potatoes = 97g.

      3 cups cooked, white rice is about 130g.

      3 cups cooked, white spaghetti = 129g.

      4 large apples = 117g.

      8 cups of cooked broccoli = 105g

      I just recently got turned on to MDA and its basic premise is similar to another format I saw a while ago that requires some counting. Basically, you take your (realistic) goal weight and multiply by 10 for base calories. (This assumes 1 hour of exercise per week.) For each additional hour, you add 1 to your base calorie calculation, so two hours total would be target weight X11, three hours X12, etc.

      From that calorie calculation you break it down to 1g of protein, 0.5g fat per pound of target body weight and the balance in carbohydrate. In some cases this will be in excess of 150g of carbs upper limit recommended on the carb curve here.

      I’ve been a “counter,” but slowly weening myself off. Plus, sites like fitday is basically “counting” and recommended by more than one person on the MDA Forum. It is a great way to “learn” food.

      As I’m new to all of this, I’m considering a “hybrid” of the two for now. Basically, 1g protein/lb, 0.5g fat/lb, and 50g carb total + approx 50-100g carb per hour of exercise (about 3.5 per week for me.)

      Great stuff on this site!

    2. I’m going to give you recommendations from two different low-carb books. One will require that you get the book, but you can find it secondhand. (I’ve seen it at Half-Price Books for a dollar in their clearance section. Goodwill might sometimes carry it too.)

      Carb intake: If you want to know what your body can tolerate, and you want to kick off fat-burning, do your carb intake Atkins-style. Start out at 20g a day for two weeks. That’s 20g digestible carbohydrate, anything that would affect your blood sugar. Fiber is a gimme because you can’t digest it.

      Then, after that 2-week period of 20g a day, increase your carb intake by 5g once a week. So in week 3 you would be eating 25g a day; in week 4 you would be eating 30g a day, and so on. Keep that up til you get to a point that you are no longer losing weight, then hold your carb intake at that level.

      You don’t *need* the Atkins book to pull this off, but for maximum efficiency and minimum grief I would at least visit their website and see what they say about recommended carb foods for each phase of the diet. You’re going to find they emphasize non-starchy veggies and (later) nuts and low-sugar fruits over anything tubery or grainy. Grains should be the very last thing you re-introduce.

      Protein intake: The book Protein Power has a couple formulas and a bunch of charts that help you establish a ballpark number for your bodyfat level, calculate your lean mass, and then determine your daily protein needs for that lean mass based on your typical daily activity level. If you get the book for no other reason, get it for that one. A lot of the formulas I’ve seen online for recommended protein intake depend on total weight and you’re not trying to maintain fatty tissue integrity with your protein intake–only your lean mass.

      Under this system I would treat beef and dairy fat and coconut oil as free foods, minimize your polyunsaturated oil intake as much as possible and when you do eat PUFAs, try to make them omega-3s as much as possible. Fish is healthy. Soybean oil is not. Et cetera.

      I don’t know how much I would worry about calories. Play with it–use FitDay or similar, and see what works for you. It’s impossible for anyone to tell you you must eat X number of calories a day because we’re not right there with you seeing the results.

      Have fun. I miss being 130. 🙁

  27. “Carbs are not used as structural components in the body”

    I am new to PB and I am liking what I am reading. One problem I had with this post is in the above statement. I just finished my biochemistry course and carbohydrates are used all the time for various structures in the body. For example, polysaccharides (carbs) are often found in conjunction with proteins and lipids in/on cell membranes and play roles in cell communication. Any thoughts Mark?

    1. I’m not Mark, but your body is capable of making the sugars it needs. (The nutritional definition of “essential” is “anything your body needs to live and function that it cannot make for itself.” There is no essential carbohydrate.) If you eat way more carb than your body needs for whatever structures, etc., then it has to be burned as fuel or stored as fat because it’s too dangerous to just leave floating around in the body.

      1. The same can be said for most fats, aside from the essential lipids (the fat-soluble vitamins and the n3 and n6 polyunsaturated fats). Beyond needing a small amount of very specific fats, our body is capable of synthesizing its own lipids (saturated fat, n9 fatty acids, and cholesterol, to name a few). The argument that there is no essential carbohydrate doesn’t imply our body has no use for them–indeed, the very fact we can turn carbs into fat but NOT vice versa has stronger implications for the versatility of carbohydrates in the diet.

  28. I came across this site today and will be incorporating these things into my eating plan. I’ve actually lowered my sugar intake over the last 4 weeks significantly and I’ve kept my carbs down to 120 to 150g per day. I put my workouts on a calendar and will start in earnest tomorrow (Monday) alternating low impact cardio, weight lifting and high impact cardio.

    I want to know how to figure out my caloric range. I’m 36, 199lbs, 5’3′, and primarly a endomorph but it easy to put on muscle.

    Mark thank you in advance for any info regarding my caloric intake.

  29. Excellent post. This is perfect for my sister who is 2 years older then me. We had a loud argument about a month ago over the fact that a calorie is a calorie. I said it was NOT while she kept on claiming that it is.

    This article is about to be e-mailed to her 🙂

  30. Since beginning this approach, I’ve tried to use hunger as a guide for what and when I should eat (within the PB guidelines, of course). Well, I’ve noticed that my calories are going down. I’m losing body fat but maintaining muscle mass. I wonder if these foods allow the cells of the body to work more efficiently and thus reduce the body’s daily caloric requirement.

  31. So, I just read all the posts and am more confused than when i started. I’m 29, 5ft9in I weigh 185lbs and need to be at 155-160. I started eating Primal three days ago and already feel the difference. Where should my calorie/carb/fat intake be if i am eating all the right foods?

  32. I was 180 pounds on my 5-6″ frame the end of may. This am I was 136 pounds. I bench 260 and leg press 450+ for 12. I have been off all grain and beans for a month or so and my strength is continuing to grow. i am very insulin sensitive. Any sugar (even in fruit) jacks me up now. I am never really hungry and have not wanted bread for a while. I absolutly dont want beans or rice. I have no desire for sugar. even creame in coffee is getting to be too sweet for me.
    For those having a tough time all i can say is stick with it. I am 41 years old and i am in better shape than when I was a Marine.

  33. well, also I am not pro-carb, I still doubt that only by eating primal I will loose weight. I tried a kind of Atkins diet for two weeks and had an eye on the cals, but was not counting…and of course gained weight! if I could just eat primally and lose weight, sorry, but that sounds to good to be true. I still believe that calories count, no matter of context. I mean, it is the law, the more in, the more weight, the less in the less weight and equal in & out = maintaining weight (and body composition). no discussion about that, the only thing I acknowledge is that with low to no carb, the hunger disappear or does not come that often. but, as said, when I eat more cals then I use with wonderful meat and fats and veggies, I will gain weight!

  34. So if we leave off proteins which are used fro reconstruction, then its about choosing where your fuel comes from; either carbs or fat. carbs are 4 cal/gr. and fat 9cal/gr. so technically I get to eat more with a low fat diet than a low carb. Now if I eat excess carbs so I get excess energy which is stored as fat then 40% of the extra carb will be used in converting glucose to fat. However, extra fat will go straight as fat. I don,t know for you but I still prefer the high carb choice… Now of course you will reply that eating carbs will spike my insulin levels etc. etc. but still, if there is no extra fuel to be stored, it does not matter if i produce lots of insulin. And considering that I am not about to be insulin resistant (which is usually triggered by being fat around the waist)then I am still better off with a low fat diet..

  35. Great article Andrew. We are UK based e-tailer and currently use a UK ecommerce platform called Tiger Commerce. Cost us £80.00 (approx $130 USD) for the year Special Offer. Normally £20 mth (approx $30 USD) .. Free 14-Day trial, No set up fees, no transactional fees, unlimited bandwidth, unlimited products and categories, unlimited storage, though a templated design you can easily change the basic appearance to suit your brand via their fairly competent and intuitive back end CP. Tiger has been a good platform for us in launching our 3 sites which we have been operating for approx 18 months. We experienced brief down time on several occasions, but their support is pretty good and responsive during working hours (GMT). I would certainly not hesitate suggesting Tiger to anyone looking at dipping their toes into the world of e-commerce on a tight budget.

  36. was wondering if you can tell me if coconut oil in a low carb diet counts in your total caloric intake? I am having a stall was wondering if i need to reduce my calories since i’ve added the coconut oil?

  37. Hi all,

    Not sure if these posts are still being read?

    I am a complete newbie to being Primal and am so excited to have started this lifestyle…HOWEVER, I have some questions and concerns due to my longstanding relationship with Conventional Wisdom. I was hoping some of the veterans could possibly help me out? Again not sure if anyway will respond to this but worth giving it a go 🙂

    Firstly, let me just introduce myself- I’m Michelle and have been in the health/fitness industry for the past 10 years. I have literally put my body through more experiments than a lab rat all in the name of becoming fitter and healthier. Last year, despite copious exercise (I teach fitness classes as part of my living) and watching my diet (I even joined Weight Watchers and got a dietician) my weight crept up 15 lbs and starting having all sorts of symptoms and was subsequently diagnosed with hypothyroid and high cortisol in December 2011. Since then it seems I can lose a couple of lbs and then regain them immediately, and I am so frustrated and depressed because I still don’t have the energy I used to but I have to fake it to my fitness classes, despite being on thyroid medication.

    Question #1: YEARS of calorie counting and/or using Weight Watchers Points have been drilled in my head so the idea of NOT counting almost causes a panic attack… I am seriously stressing about gaining more weight. Even though I haven’t been losing, I haven’t been GAINING. I am not doing this for weight loss, I am doing it to feel good, but I also do need to take of this (thyroid) weight.

    Fat = EVIL on ALL of those programs so I am really battling the idea of eating so much fat due to the high caloric content. My Livestrong account says I need about 1350 calories a day for my height and weight to lose 1-2 lbs a week. I couldn’t resist finding out my nutrition totals (especially carb g) so logged my first day eating Paleo and I was at 1900 due to the additional fat! This is WAY more than I usually eat, mind you I have had to do over 2 hours of fitness classes today so I was hungry! Mark says you have to listen to your body but I have no idea how to do that anymore after so many years of believing I had to be hungry to lose weight. Should I keep my fat % the same but just try to eat 1350 (which is also incidentally my Basal Metabolic Rate, according to a Nutrition Course that I took, taught by Conventional Wisdom).

    Sorry for this really long post, I am overly gregarious, it seems, even on paper! I would be so THRILLED if I got a response.

    1. Hi Michelle,

      I was just reading through some past posts here on MDA to try to remind myself more about getting into ketosis and I saw your comment.

      I’m not sure exactly how to answer but I think what you are for asking is for some reassurance about this way of eating. I can say that all that personally matters to me when I eat this way, apart from the quality of the food I’m eating, is the total amount of carbohydrate that I ingest. That is the sole determining factor for weight loss for me. And I am pretty inactive apart from walking and mini-trampolining. Both gentle exercises (trampolining good for its effects on the endocrine system through stimulation of the lymphatic system, which helps me not feel sluggish… google this to find out more, perhaps it could help with your thyroid).

      I am not sure how much carbohydrate you either need or can tolerate, seeing as you must be highly active from your fitness classes. This is a personal threshold.

      Eating primally should take care of the ‘feeling good’ part (apart from any temporary carb flu/die off that you ay experience). If you only eat proteins and healthy fats then your body will literally not let you overeat. It’s impossible. The only way this could happen is if you absolutely drown everything in oil to the point of drinking it down! Because then you are, within seconds, consuming huge quantities of calories of which you would have had to eat a massive quantity of the raw food.

      For example, months ago, I was doing very low carb (atkins) primal eating. I got the ketostix to measure the ketones in my urine (much better way of measuring your efforts of weight loss than calorie counting!). They were dark purple but I wasn’t losing any body fat. I was doing a practically zero-carb diet. I then did some research and realised that the ketones coming out of me could be just from the fat I was *eating* and not actually burning. I had been cooking my eggs and bacon in butter and oil and then (in an attempt to speed up ketosis) almost drinking the oil out of the pan, tablespoons at a time. I think I was just unnecessarily consuming too many extra calories like that!

      If you’re not doing that then you can pretty much eat as much fat, protein and salad as you want and you should burn fat. I still drizzle oil over everything and have things drowning in it… I just don’t then drink the oil up as well! However, if you’re also highly active then you’d probably burn it all of later. Or the excess would make you feel so full that you wouldn’t want to eat later on. (Fat is the only substance that doesn’t raise insulin at all). Incidentally, I didn’t gain weight the first time, even though I wasn’t losing.

      There is nothing wrong with fat: just keep reminding yourself of that fact. If our bodies store everything surplus as fat then they must want that as a fuel source.

      Did this help at all?

      By the way… I’m not sure about what amount of carbohydrate you should eat relating to your fitness levels/thyroid problem. I know I have a tendency to get lethargic and sluggish which is, I’m sure, related to thyroid (although I don’t have a diagnosed problem). Carbs give me temporary energy but make me feel terrible overall. Once I am past the difficult carb-withdrawal phase, and into fat-burning instead of glucose-burning, it suits me much more and I have so much more energy, clear thinking and motivation. But that’s just me!

  38. After many failures you always find the success, the key here is PROTEIN, LOTS OF PROTEIN for fat loss

    1.5 grams of protein x BW
    0.4 grams of fat x BW
    50-100 grams of carbs Max

    So, if you weight 200 pounds.

    300g of Protein x day
    80 g of Fat
    70 g of Carbs

    1200 calories from Protein
    720 calories from Fat
    320 calories from Carbs

    This never fails.

  39. There’s a bit of misinformation in this article which should be noted: our body CANNOT create glucose out of any fat or fat-derived ketones. The only part of a triglyceride which can be converted to glucose is the glycerol bit. All fats and ketones can only be utilized through the TCA cycle, which means that they are incapable of supporting anaerobic exercise.

    So while muscles certainly don’t require carbs to perform work, they will sorely miss them. Without carbs, our muscles are limited to low-intensity work, except for the brief few seconds of energy powered by the phosphocreatine system, which translates to decreased performance.

    1. Brian,
      This does not make sense to me. If primitive hunter-gatherers could not produce muscle growth and explosive energy without carbs, they would not be capable of the next hunt… I am under the impression that pretty much every part of the body can operate without carbohydrate foods. And remember, nobody is eating pure fat. Most dietary fat comes with protein. And protein can be broken down to produce glucose through gluconeogenesis. None of the bodybuilders I have known that kept a keto diet had any difficulty.after the transition. It is very much like the standard bodybuilder’s protein-sparing fast, except with fewer restrictions.

  40. Hi there Mark

    I was wondering if my daily calorie intake should change to as and what I’m doing. E.g more on training days and less on non training days and should I work it on a weekly bases and change and manage as I go ?

    Thanks a mill

  41. So what you are saying is that if you eat 1600 calories from pure white sugar and burn 1800 calories during the day. You will more likely than not feel like sh*t and be skinny and have other issues. But you will lose weight. So if you eat 400g of carbs a day you will still lose weight. That has to be clearly said too from time to time.

    A sportsman that burns 3600 calories a day. No problems to slim down with 900g of carbs xD. Just mention that too from time to time please. You can even add how unhealty it is, but please don’t act like it is not true. Thanks.

  42. Thanks for every other informative site. The place else may
    just I am getting that type of info written in such a perfect means?
    I’ve a project that I’m just now running on, and I’ve been at the glance out for such info.

  43. I have been a fan of this train of thought when it comes to food. Take in, whole, organic foods, and you don’t have to worry as much about counting calories, due to the fact that your body is getting nutrients it needs. Obviously, if you eat a block of cheese a day, you probably aren’t going to end up with the results that you’re looking for lol. Great write up!

  44. (Is this a re-print of an 11-year-old post? Bunch of the comments are from 11 years ago… but if so, it seems to have aged well.)

    Under “Not Training”, the comment “…so the protein you eat will be wasted or burned for energy” begs the question:

    What does wasted mean?

    And this is important, not just nit-picky. We are basically thermodynamic machines converting the energy in our food into our lives: staying warm, moving, thinking.

    If some of the caloric content of food is wasted, where does it go? Heat? Our temperature would go up. Storage? Our fat would increase, and our weight.

    Or do we just poop out some portion of usable caloric content (a question I’ve never seen addressed).

    “Wasted” just leaves me wondering where it really goes…..

    1. The note below the citations says that it’s a “substantially revised” version of the original. Three of the citations post-date the original.

  45. Thank you for returning to this important concept! The public has been so saturated with the calorie counting concept that it calls for repeated clarification.
    However, I am saddened by all the commentary I see from many posts that are talking about measuring everything one eats! In micro-grams!! That would make me crazy!
    I like to see both the primal diet, and keto versions of the primal diet, kept simple and straightforward. Just eat real meat and real vegetables! And if you do that, your appetite will be more controllable, and you will be far less likely to overeat.In other words, there should be no need to figure your micro-grams of anything! In addition, your energy level will be good, and your overall health will improve.

  46. Well, I’m a 55-year-olld male, approx. 6 ft. and my weight ranges about 139-144 lbs. I have had ulcerative colitis, inflammation of the colon or “inflammatory bowel,” since 1999. After the initial medical ordeal from about July 1999-April 2000, I went through a lot of “trial and error” with foods, especially from 2000-2005 including several relapses of colitis in those years.

    Unfortunately, it took me years to learn about the importance of nutrition and the effects that some foods have on the digestive system. If only establishment doctors knew about or understood the importance of nutrition!

    I’d really like to weigh more, but I can only have so much food per day. And I don’t want any more bleeding-BM relapses! I think my daily calories add up to about 2000. I don’t want to be drinking Ensure again, like I did for too many years from 2000 to 2013.

    And my carbohydrates per day might be a little high, but I rely on things like concord grape juice, extra virgin olive oil, organic whole milk and organic butter, not just for nutrition but for extra calories that I know I need.

    So here is what I have per day, in total numbers (not all at the same time): 5 hard-boiled eggs, one slice of white bread toast, two small pieces of white meat baked chicken, a baked potato without skin, 4 servings of organic unsalted butter (1tbsp is a serving), 6 servings of extra virgin olive oil (1 tbsp each), 4 servings of organic whole milk, 2 servings of carrot juice (thank God for carrot juice), 2 servings of organic apple juice, 2 servings of concord grape juice (8 oz. each for milk and the juices).

    And also supplements including approx. 2 to 3 scoops of whey protein (that’s actually good for the colon), 3 half-teaspoons of guar gum for soluble fiber, and various vitamins, including C, D, K2, B-complex, etc.

    I can’t have most vegetables and fruits because they have insoluble fiber, also nuts, coffee, red meat, and I can’t even have fish. I really tried with the fish, cooked, canned, different varieties, but there’s something about fish that causes me problems. It’s been quite an ordeal for quite a lot of years now with ulcerative colitis.

    So, I’m not sure what else I can do to gain more weight, because 140-144 is “okay,” but still a little low, in my view. And I do exercise every morning. I was drinking Ensure, but that has a lot of “crap” including corn oil and sugar and a lot of synthetic chemicals, and I want to avoid processed foods. Maybe someone is familiar with all these things and knows of some kind of food to add that’s not an irritant on the lower digestive area. Thanks, and sorry if this comment is too long.

  47. Hi everyone ^^

    I’m a long time reader and pretty much cut my teeth on removing wheat, following a primal or ancestral approach to health, and noticed great changes over the years (essentially from 2011 up until last year). As a current student of evidence-based nutrition through Mac-Nutrition University, I felt compelled to reply to a few points from this article.

    The main point I’d like to address is that, while calorie labels can sometimes be inaccurate (almonds being a well known example since the body processes them differently than a bomb calorimeter), that doesn’t negate the laws of thermodynamics, meaning that energy balance will be upheld and energy cannot simply disappear. If one is lightly active or sedentary and they consume excessive amounts of calories, the energy has nowhere to go but to be stored as fat. If one’s body has higher energy requirements, for example from high intensity exercise, high NEAT levels, slightly increased energy requirements from additional lean mass, or generally moving around often, and sufficient calories aren’t consumed to power those things, then the body will draw on fat stores assuming protein intake is sufficient to spare/build muscle. This has been tested myriad times in ward studies, and while it’s true that we don’t live in a metabolic ward, that doesn’t falsify the underlying results which describe, with as few confounding variables as possible, our physiology.

    That being said, Mark is certainly right in pointing out that calorie counting is daunting and difficult for many people. Fitness trackers demonstrably overestimate the calories burned in a workout, but they’re great for tracking activity and step levels and have been shown to increase adherence to a healthier lifestyle. Counting calories is certainly not necessary for fat loss; as Mark said, protein is highly satiating and requires the most amount of energy to burn, so by increasing protein (1.6g/kg bodyweight is a good place to start for pursuing “optimal health”) and fiber (within reason, roughly about 30g per day) with each meal it naturally becomes easier to stop eating more because you’re simply not hungry.

    By eating a higher food volume through lots of veggies and better nutrient distribution by way of more protein and less processed foods that are more calorically dense compared to whole foods, one can see how steadily losing fat would follow without actually counting the reduced amount of calories they’re now consuming.

    Fat is essential to eat for numerous reasons, as Mark has discussed before, and very generally a good level to aim for is 0.5g/kg bodyweight. The numbers I’ve provided are based on research, but everyone is different so n=1 will always apply because there is no one size fits all diet.

    Metabolic flexibility is a real phenomenon that most people who are overweight begin to lack. This refers to the body’s ability to switch between stored fat and glucose as an energy source depending on energy availability and the situation. For some people, reducing CHO intake from very high levels to low or moderate levels helps to improve this flexibility. This improvement is furthered by exercise, and generally healthy people typically have good MF.

    While everyone has a preference for different eating styles, fat loss and health improvements in the long term are dictated by adherence to a lifestyle in which food is consumed responsibly (most of the time) and according to one’s goals, exercise and movement are incorporated regularly, and stress and other social/mental health factors are managed to the best of one’s ability. Some people really like keto, or primal/paleo, or any number of styles of eating, but it always comes down to what someone enjoys and can stick to forever.

    I didn’t mention genetics because while they certainly can affect things in some cases, such as one’s ability to efficiently process fat, they can be managed, and there are currently no evidence based genetics based diets. Mental health is also crucial to adherence, and those memories/experiences/emotions associated with foods are often the primary barriers people have to changing their habits, but I’ve already written a wall of text and these things could easily be an entire other post. If you read to the end, I very much appreciate your time and attention.


    1. Sam,
      Very interesting thoughts. I wholeheartedly agree that thermodynamic laws are inviolate, but I think we over simplify how the body manages the energy content of food. Regarding in particular your 2nd paragraph ending with: “……has nowhere to go but to be stored as fat.”:

      First, as you point out, the caloric value of foods, as measured in a bomb calorimeter, differs from the calories the human body extracts from food. This is complex and rarely addressed, either regarding differences between foods (e.g. almonds), differences between people (does everyone extract the same amount of energy from a given food?), and differences depending on metabolic state (does the body extract more or fewer calories if fasted, not fasted, glycogen reserves high or low, etc.?)

      Second, as I mentioned in an earlier comment, I’ve never seen a study on the caloric content of our waste products (feces in particular). Does the body sometimes eliminate caloric content it could otherwise use in some metabolic states? I have no idea. I’ve watched for years for a study on this question, and haven’t seen it addressed.

      Third (and I wonder if this is the biggest confounder), the efficiencies of the many biological processes involved in using and storing/retrieving energy from food for cellular activity (e.g. storing food as fat, extracting triglycerides from stored fat, gluconeogenesis, and many more), mean that the energy available for actual physical activity is only some fraction of the caloric intake. The rest of course ends up as waste heat after powering all those biological processes.

      So… trying to measure energy in humans as calories in vs. physical activity is so confounded by complex biological processes that to conclude that someone gains weight merely because they eat too many calories seems to me to be a significant oversimplification.

  48. In a recent study, it has been found that different food contains different calories value. When someone takes high-fiber foods, such as nuts & vegetables, we only be able to absorb three-quarters of the calories contained in it and the rest part is excreted from the body as unused. Therefore, its bit tough to say that all calories contain the same energy.