The Definitive Guide to Protein

guide to proteinProtein is an incredible essential macronutrient. Fat is plentiful, even when you’re lean, and there are only two absolutely essential fatty acids; the rest we can manufacture from other precursors if required. Carbs we can produce from protein, if we really must, or we can just switch over to ketones and fats for the bulk of the energy that would otherwise come from carbs. Protein cannot be made with the raw material available in our bodies. We have to eat foods containing the range of amino acids that we need.

In other words, protein is incredibly important—which is why today I’m writing a definitive guide on the subject. After today’s post, you’ll have a good handle on the role protein plays in the body, how much protein you need to be eating, which foods are highest in protein, and much more.

First, what roles does protein play in our bodies?

It helps us build muscle.

We use it to construct new cells, muscles, organs, and other tissues.

It’s a chemical messenger, allowing us to turn on and turn off genes.

It forms the fundamental substrates used to manufacture enzymes, DNA, and hormones.

It can even be a fuel source, either directly or through conversion into glucose.

Now, am I saying that the steak you eat directly becomes a thyroid hormone? Does chicken breast turn into DNA?

No. But the strings of amino acids and peptides that make up proteins are eventually broken down and cobbled back together to fulfill all the roles I describe. Every bite of protein you consume contributes toward maintenance of your physiology. And we can’t make new protein. We have to eat it.


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What’s the Recommended Daily Protein Intake?

If you go by the official numbers, the Recommended Daily Allowance (RDI) for protein is 0.8 grams of protein per kilogram of bodyweight, or 0.36 g protein/lb. That’s what the “experts” say to eat. That’s all you “need.” I disagree, and I’ll tell you why down below, but there’s the official answer.

Sufficient is one thing. Optimal is another. In reality, the amount of protein required for optimal health and performance is different for every population.

Protein Intake for Athletes and Exercisers

Athletes need more protein than the average person, but perhaps not as much as most fitness enthusiasts think (or consume). A 2011 paper on optimal protein intakes for athletes concluded that 1.8 g protein/kg bodyweight (or 0.8 g protein/lb bodyweight) maximizes muscle protein synthesis (while higher amounts are good for dieting athletes interested in preserving lean mass), whereas another settled on “a diet with 12-15% of its energy as protein,” assuming “total energy intake is sufficient to cover the high expenditures caused by daily training” (which could be quite high).1 2 One study even found benefit in 2-3 g protein/kg bodyweight (0.9-1.4 g protein/lb bodyweight) for athletes, a significant increase over standard recommendations.3 That said, I wouldn’t be too quick to discount anecdotal evidence or “iron lore.” A significant-enough portion of the strength training community swears by 1-2 g protein/lb bodyweight that it couldn’t hurt to try if lower amounts aren’t working for you.

Protein Intake During Weight Loss

Weight loss involves a caloric deficit (whether arrived at spontaneously or consciously). Unfortunately, caloric deficits rarely discriminate between lean mass and body fat, while most people are interested in losing fat, not muscle/bone/tendon/sinew/organ. Numerous studies show that increasing your protein intake during weight loss will partially offset the lean mass loss that tends to occur. In obese and pre-obese women, a 750 calorie diet with 30% of calories from protein (about 56 grams) preserved more lean mass during weight loss than an 18% protein diet.4 Another study in women showed that a 1.6 g protein/kg bodyweight (or 0.7 g protein/lb bodyweight) diet led to more weight loss, more fat loss, and less lean mass loss than a 0.8 g protein/kg bodyweight diet.5 Among dieting athletes, 2.3 g protein/kg bodyweight (or a little over 1 g protein/lb bodyweight) was far superior to 1.0 g protein/kg bodyweight in preserving lean mass. And, although specific protein intake recommendations were not stated, a recent meta-analysis concluded that high-protein weight loss diets help preserve lean mass.6

Protein Intake When Injured

Healing wounds increases protein requirements. After all, you’re literally rebuilding lost or damaged tissue, the very definition of an anabolic state, and you need protein to build new tissue. One review recommends around 1.5 g protein/kg bodyweight or close to 0.7 g protein/lb bodyweight for injured patients.7 Children recovering from illness or injury may need up to 2.5 g protein/kg. If you mess this up and undershoot your protein intake during recovery, you will compromise your healing.

Protein Intake for Seniors

The protein metabolism of the average senior citizen is compromised. They need more protein to do the same amount of “work.” The protein RDA is simply not enough for seniors, who lose thigh muscle mass and exhibit lower urinary nitrogen excretion when given the standard 0.8 g protein/kg bodyweight.ref]https://www.ncbi.nlm.nih.gov/pubmed/11382798[/ref] What’s good for the goose may not be good for the elderly, frail gander. More recent studies indicate that a baseline intake of 1.0-1.3 g protein/kg bodyweight or 0.5-0.6 g protein/lb bodyweight is more suitable for the healthy and frail elderly to ensure nitrogen balance.8 That said, active seniors will do better with even more and evidence suggests that increasing protein can both improve physical performance without necessarily increasing muscle mass and increase muscle mass when paired with extended resistance training in the elderly.91011

How Much Protein on Keto?

What about another population entirely: ketogenic dieters. We’ve got a lot of those around here, so this is important. If you’re on a keto diet, should you restrict protein? I mean, doesn’t extra protein just convert directly into glucose?

Our livers only convert protein into glucose when we—for whatever reason—need more glucose. It’s demand, not the supply. And since keto-adapted people are running mostly on fat and ketones, they have a lower requirement for glucose and are much less likely to trigger the kind of perceived glucose deficiency that necessitates gluconeogenesis.

Extra protein can however impair ketogenesis by contributing oxaloacetate donors to the Krebs cycle. With oxaloacetate, fatty acids enter the Krebs cycle and are fully oxidized and turned into ATP, the body’s energy currency. Without oxaloacetate, fatty acids can’t enter the Krebs cycle and are instead converted into ketones to generate energy.

If you’re dealing with cognitive decline, elevated inflammation, or any other condition that requires or may improve with deep ketosis, aim for a lower protein content (10-15% of calories). Get those high ketone levels, see how it feels, and see if that’s the protein intake for you. Start low, really revel in those high ketone readings, and stick with them if you’re improving.

If you’re losing weight (or trying to), eat closer to 15-30%. For you, the ketone readings aren’t the biggest focus. How you look, feel, and perform are your main concern. Eating slightly more protein will increase satiety, making “eating less” a spontaneous, inadvertent thing that just happens. It will also stave off at least some portion of the lean mass accretion that occurs during weight loss; you want to lose body fat, not muscle.

If you’re trying to gain large amounts of muscle, eat closer to 20-30%.

Understand, however, that everyone is unique. For some, protein is deeply anti-ketogenic—eating too much protein will knock you out of ketosis almost immediately. For others, protein has little to no effect. Or if it has a momentary nullifying effect, you can quickly slip back into ketosis. Unless deep ketosis is medically necessary, don’t worry about protein too much either way. There are studies of “modified ketogenic diets” where protein goes as high as 30% of calories and subjects still get the benefits.12

High Protein Benefits

Beyond supporting the basic underpinnings of human physiology, eating more protein than the RDI offers extra benefits.

Protein Satiety

As a fundamental biological motivator, hunger can’t be ignored forever. Eventually you crack, and the diet fails. Eventually, you’re going to eat. Where extra protein helps is adding satiety. Successful fat loss comes down to managing your hunger; protein helps you manage it without relying on sheer willpower.

Protein For Muscle Gain and Muscle Retention

To increase muscle protein synthesis, you need two primary inputs: resistance training and protein intake. You can lift all the weights in the world, but if you’re not eating enough protein, you won’t gain any muscle. You can’t make extra, it has to come from outside sources.

And then during active weight loss, upping your protein intake will minimize the loss of muscle that usually accompanies fat loss. In women, for example, cutting calories while keeping protein higher than normal led to better lean mass retention than cutting the same number of calories and keeping protein low.13 Simply put, more protein tends to enhance fat loss and preserve muscle.

Protein to Increase Energy Expenditure

Metabolizing protein is costlier than metabolizing fat and carbohydrates: it takes extra energy to process protein than it does to process the other macronutrients. This increases the amount of calories you expend, simply by eating more protein. Thus, higher protein diets increase energy expenditure relative to diets lower in protein.

Higher Micronutrient Intake

While we love our fat-soluble vitamins around here—your vitamin Ds, your vitamin K2s, your retinols, your vitamin Es—we musn’t forget about our B-vitamins and minerals. Those latter two groups come bound in the muscle meat. The more whole food-based protein we eat, the more micronutrients we’ll take in.

Protein Foods: Where to Get Your Protein

The best sources of protein for humans are animal foods. Meat, fish, fowl, shellfish, eggs, and dairy all contain the most bioavailable form of protein: animal protein. Makes sense when you consider that we are animals, and we use the protein we eat to build new animal tissues in our own animal bodies. Of course animal protein will be better and more efficient at doing protein-y things than plant protein.

  • Following resistance training, soy protein blunts testosterone production in men.14
  • In both the young and the elderly, whey promotes greater muscle protein synthesis than soy protein.15
  • Compared to milk, soy protein results in less hypertrophy following resistance training.16
  • Women who consume animal protein have greater muscle mass than female vegetarians.17

We can also confirm this by studying the Biological Value (BV) of a given protein source. The BV describes the proportion of protein in a food that becomes incorporated into the consuming organism’s tissues, with 100 being best.

  • Egg protein: 100 BV
  • Whey isolate: 100 BV
  • Milk protein: 91 BV
  • Beef: 80 BV
  • Casein: 77 BV

And then:

  • Soy protein: 74 BV
  • Wheat gluten: 64 BV
  • Pea protein: 65 BV

Another factor to consider is that animal protein is complete; it contains all essential amino acids—those amino acids which we cannot produce ourselves and must obtain from outside sources. Plant proteins tend to be incomplete. No individual plant protein is complete, except for perhaps potato protein (but the absolute levels of protein in a potato are too low). If you want to go all plant, you have to combine different ones to hit all the amino acids you need.

So in theory you could get your protein from an algorithmically-derived blend of gluten powder, pea protein, rice protein, and fermented free range soy. Or you could just eat 5 eggs for breakfast (30 grams), a Big Ass Salad with a can of oysters (11 grams), some cheese (8 grams), and a can of sardines (24 grams) on top for lunch, and a ribeye for dinner (40-80 grams, depending on size).

I know what I’d choose. I know what’s easier, what’s more delicious.

Collagen Protein

Collagen protein is the type of protein you get from connective tissue in meats. You can slow-cook tougher cuts of meat until they’re tender, or simmer a batch of bone broth to get your collagen.

Collagen is so important that I consider it the fourth macronutrient. It contains amino acids that aren’t as plentiful in muscle meats and other protein sources, so it helps your body complete the amino acid chains that would otherwise be limited. You get more benefit out of the other protein you eat by eating collagen-rich foods or supplementing with a hydrolyzed collagen protein supplement. You can read more about collagen here.

How about you, folks? How do you get your protein? How much do you eat per day?

TAGS:  protein

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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37 thoughts on “The Definitive Guide to Protein”

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  1. I don’t get how anyone can hit these numbers. I lift pretty heavy weight for my frame. I am 5’11 and work up to a max of 315 on the bench before doing reps at 225, 185, and 155. When I’m at low body fat I weigh about 210-215.

    After a 1st meal of 3 eggs and 4 strips of bacon, I’ve only managed 44 grams of protein. I just cannot conceive of eating another 100 grams+ over the next 8 hours. How does anyone do this?

    1. Chicken… With fatty cuts of meat it really is hard. I’m a 128lb female and regularly consume 100-150g protein, a lot of times unintentionally, because chicken is cheaper than other meats.

    2. I am not athletic and agree very hard to hit the protein numbers, especially when eating eggs or beef, my primary sources. Is the g/pound formula based on a person’s total weight, optimal weight, or lean body mass?

      1. I’m surprised Mark didn’t address that issue, Colleen. Obviously someone weighing 400 pounds shouldn’t eat as much as the guidelines suggest.

        This is not my first protein research rodeo. And this question seems to never get answered.

        I go with ideal body weight. Seems logical to me. No sense ramping up protein intake for fat cells.

    3. Those are fatty foods. To up the protein, very lean beef, chicken breast w/o the skin, most fish.

      I’m not a weight trainer but my dietary plan is aim for 120-150g of protein a day as priority, keep carbs down to 50 most days, fats fall where they may.

  2. I’m not big into weighing, counting, or measuring my food. In fact, I never bother with that sort of thing. I’ve learned enough about good nutrition over the years to know what to eat and what to mostly avoid.
    Regarding protein, for me it’s self-limiting. When my body has had enough, I lose interest in eating any more of it. That’s my own rule of thumb–not how many grams per pound of body weight someone else thinks I should be eating. It might not work for everyone, but paying attention to my body’s needs has always served me well

  3. Who in the US ever measures anything grams (other than drugs)? Please provide recommendations in ounces!

    1. Because all food portion information is in grams.

      Yes, you may eat 6 oz of something, but all of the components like protein, fat, and carbs will be in grams.

      Science, ya know?

  4. Holy crap, according to these studies I’ve definitely been overeating protein these last few years. I guess I always assumed a 1/4lb per meal was just the easy go-to. I do have a few pounds of excess body fat that I would like to get rid of so perhaps I should reevaluate a few of my meals.

    1. Those values refer to the protein content of the food, not the actual weight of the “protein” item you are eating.

  5. Great article Mark, good to see you have come round to a ‘high protein’ point of view! I remember when you were on Dave Asprey’s Bulletproof Radio podcast a year or 2 ago, and you agreed with Dave that high protein diets of more than 150 grams protein per day would be harmful. If I remember correctly, you were both saying that if you ingest high amounts of protein, the body burns protein extremely inefficiently, producing many harmful free radicals (relative to burning fats or ketones). This didn’t quite hang with me at the time as I have never seen any evidence to support that. Have you changed your point of view now? Or were you just agreeing with Dave to be polite?!! What about higher protein driving excessive growth and cancer a la Dr. Ron Rosedale/ Dr. Valter Longo?

  6. I’m 64, 5’9″, 155lbs. (similar to Mark) and eat between 60-100 gm. of protein a day. My weight never fluctuates more than a lb. here and there. Two intense bodyweight workouts and one sprint session a week and I’m good to go. I may up my protein intake a hair as I get older, but I feel fine with the amount I get, so far.

  7. What I’ve been trying to figure out is proper protein pacing. I am familiar with all these recommendations, so I have been shooting for a top end of 200 grams a day – but I know there is an upper limit for how much you can process at one time. I’ve heard this is around 30-40 grams. First of all, what is “at one time”? What is the minimum meal spacing? It seems like properly spacing 200 grams within my waking hours means not only a lot of meals, but also no room for any IF.

    1. Define “process”. I think there is likely an upper limit for protein synthesis (which is where the 30g figure comes from), however I’m not sure that this is the same for everyone. I personally noted though that eating more than 40g tends to knock me out of Ketosis.

    2. I don’t buy the 30-40g protein limit at all. From an evolutionary perspective, humans were opportunistic and ate as much as they reasonably could in one sitting, knowing the timing of the next meal may be uncertain. Thirty grams of protein is equivalent to about 5 eggs, or a little less than 400 calories. There’s no way our ancient ancestors ceased eating an animal, their primary food source, at that rate of consumption.

  8. I’m 170lbs, 5’10” and eat 160-180 g protein/day, about 120 g fat and almost always under 100g net carbs. It’s working well for preserving lean muscle mass during a slight calorie deficit.
    Example meal plan for me
    Meal 1: 3 eggs, can of salmon, avocado mayo, one whole avocado
    Meal 2: Big piece of leftover meat 6-10 oz, some Wholly guacamole, maybe salad w/ EVOO (although I’m experimenting w/ a carnivore-ish approach)
    Occasional post workout shake: grassfed whey w/ avocado, banana, cacao and some organic PBFit powder
    Meal 4 Some big piece of meat (chicken, steak, venison, salmon) with some steamed or roasted veggies, maybe w/ some EVOO if I need more fat/calories

  9. Semi plant based eater here (long term ulcerative colitis protein tolerance experimentation driven) I eat oysters a few times a week and a piece of fatty wild fish here and there but am mainly vegan with primal principles.

    I really love eating high quality Spirulina powder (oddly find it quite tasty too) and am wondering if it is indeed a whole protein as suggested by vegan websites. I’ve heard statements to the contrary and would love your input Mark.

    Also- any upper limit on how much to eat daily. I sometimes do 50-60 grams. Any dangers with that amount?

    Cheers, and love your work Mark!

    1. Well, it took me a whole minute to find out the answer to your question. And I suspect it also resides on the jar you have.

      Algae? High protein? Like saying kale has it. The one spec I looked at says there are 2 grams of protein per teaspoon. Worthless. And probably not very complete protein.

  10. Another great article and well timed. I’ve just qualified as a PT/nutritional advisor and am paying a lot of attention to the area of protein. After years of dieting I’m really coming round to the concept of building and repair. As a nearly 49 year old woman who regularly trains, I have a new appreciation for keeping my body well fed. Thanks for the guidance and the details for different population types.

  11. Hey Mark,

    Thank you for the inspiration! You light my PHC fire every time!!!

    I would like to ask you to share your thoughts about the AAU (amino acid utilization) of collagen being 0%. There are claims that this means that most of the collagen we eat ends up as sugar or carbs…(Source: Search for the perfect protein, Minkoff, D)

    Stay Balanced,
    Roderick Smeijer
    The Netherlands

  12. Albumin is the great protein. Problem is the difficulty of ingesting it

  13. Mark, I love it when you refer to grams of protein per kg or lb of bodyweight, as you do in some of the guidelines above. But then you switch to percentages, which is much harder (almost impossible for me) to determine. I understand that the percentages will be more precise and thus more valuable for the goals specified, but could you possibly provide a range of numeric values for protein in these instances in terms of grams/bodyweight? Thanks!

    1. This wouldn’t really be an option Robin as everyone will have such different targets for daily calorie intake.
      Men & Women are usually different
      Activity level makes a difference
      Type of activity makes a difference.

  14. Mark Like your stuff. After. Surgery , hormone treatment (8 mon) and radiation I am now trying. To get some muscle back. Using intermittent fasting 16 hr and low carb diet. Following keto diet as close as possible. Not able to get carbs to 50g daily . Any thing I can do?
    Started at 238 # 3 years ago. Now 200 and struggling to go back down to 190

    1. Brent, I don’t think you are eating enough protein from what you said.Your body is in “starvation mode” & hanging on to every calorie. You had surgery AND radiation. Both require extra calories for healing as well as protein. For a couple of weeks, try majorly increasing your protein, continue to eat lower carb vegetables, no sweets.Eat about every 3-4 hours during waking hours. Reevaluate your energy levels. Sometimes you need to take a “holiday” from all low carb diets to reset your metabolism.

  15. I love your Posts BUT I am old and all that Grams, Kilograms, etc. just LOST me. It does Not tell me how much to each by SIZE.

    1. Hi Donna, the size of the piece of protein-providing food will depend on the type of food so this isn’t really an option.
      The size of a piece of beef will be different to the size of a piece of chicken will be different to the size of a piece of fish.
      I realise weighing things can by trying but after a few times I think you’ll find that you then have a good sense of the ‘size’ that is appropriate for you.

  16. Hi Mark. My wife considers cutting out meat from diet but not the fish. She loves fish. Would fish meat provide enough protein for a healthy diet?

    1. Hi Peter, you would need to research the grams of protein in different fish types and then just carry on calculating how much your wife is ingesting.
      I’m not sure if there are any with the Amino Acid profile of fish (I know it’s complete in meats) but she will need to be careful in which fish she chooses in case of mercury toxicity.

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