Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
4 Jul

What Does It Mean to Be Fat-Adapted?

When describing someone that has successfully made the transition to the Primal way of eating I often refer to them as “fat-adapted” or as “fat-burning beasts”. But what exactly does it mean to be “fat-adapted”? How can you tell if you’re fat-adapted or still a “sugar-burner”? I get these and related questions fairly often, so I thought I’d take the time today to attempt to provide some definitions and bring some clarification to all of this. I’ll try to keep today’s post short and sweet, and not too complicated. Hopefully, med students and well-meaning but inquisitive lay family members alike will be able to take something from it.

As I’ve mentioned before, fat-adaptation is the normal, preferred metabolic state of the human animal. It’s nothing special; it’s just how we’re meant to be. That’s actually why we have all this fat on our bodies – turns out it’s a pretty reliable source of energy! To understand what it means to be normal, it’s useful examine what it means to be abnormal. And by that I mean, to understand what being a sugar-dependent person feels like.

A sugar-burner can’t effectively access stored fat for energy. What that means is an inability for skeletal muscle to oxidize fat. Ha, not so bad, right? I mean, you could always just burn glucose for energy. Yeah, as long as you’re walking around with an IV-glucose drip hooked up to your veins. What happens when a sugar-burner goes two, three, four hours without food, or – dare I say it – skips a whole entire meal (without that mythical IV sugar drip)? They get ravenously hungry. Heck, a sugar-burner’s adipose tissue even releases a bunch of fatty acids 4-6 hours after eating and during fasting, because as far as it’s concerned, your muscles should be able to oxidize them (PDF). After all, we evolved to rely on beta oxidation of fat for the bulk of our energy needs. But they can’t, so they don’t, and once the blood sugar is all used up (which happens really quickly), hunger sets in, and the hand reaches for yet another bag of chips.

A sugar-burner can’t even effectively access dietary fat for energy. As a result, more dietary fat is stored than burned. Unfortunately for them, they’re likely to end up gaining lots of body fat. As we know, a low ratio of fat to carbohydrate oxidation is a strong predictor of future weight gain.

A sugar-burner depends on a perpetually-fleeting source of energy. Glucose is nice to burn when you need it, but you can’t really store very much of it on your person (unless you count snacks in pockets, or chipmunkesque cheek-stuffing). Even a 160 pound person who’s visibly lean at 12% body fat still has 19.2 pounds of animal fat on hand for oxidation, while our ability to store glucose as muscle and liver glycogen are limited to about 500 grams (depending on the size of the liver and amount of muscle you’re sporting). You require an exogenous source, and, if you’re unable to effectively beta oxidize fat (as sugar-burners often are), you’d better have some candy on hand.

A sugar-burner will burn through glycogen fairly quickly during exercise. Depending on the nature of the physical activity, glycogen burning could be perfectly desirable and expected, but it’s precious, valuable stuff. If you’re able to power your efforts with fat for as long as possible, that gives you more glycogen – more rocket fuel for later, intenser efforts (like climbing a hill or grabbing that fourth quarter offensive rebound or running from a predator). Sugar-burners waste their glycogen on efforts that fat should be able to power.

Being fat-adapted, then, looks and feels a little bit like the opposite of all that:

A fat-burning beast can effectively burn stored fat for energy throughout the day. If you can handle missing meals and are able to go hours without getting ravenous and cranky (or craving carbs), you’re likely fat-adapted.

A fat-burning beast is able to effectively oxidize dietary fat for energy. If you’re adapted, your post-prandial fat oxidation will be increased, and less dietary fat will be stored in adipose tissue.

A fat-burning beast has plenty of accessible energy on hand, even if he or she is lean. If you’re adapted, the genes associated with lipid metabolism will be upregulated in your skeletal muscles. You will essentially reprogram your body.

A fat-burning beast can rely more on fat for energy during exercise, sparing glycogen for when he or she really needs it. As I’ve discussed before, being able to mobilize and oxidize stored fat during exercise can reduce an athlete’s reliance on glycogen. This is the classic “train low, race high” phenomenon, and it can improve performance, save the glycogen for the truly intense segments of a session, and burn more body fat. If you can handle exercising without having to carb-load, you’re probably fat-adapted. If you can workout effectively in a fasted state, you’re definitely fat-adapted.

Furthermore, a fat-burning beast will be able to burn glucose when necessary and/or available, whereas the opposite cannot be said for a sugar-burner. Ultimately, fat-adaption means metabolic flexibility. It means that a fat-burning beast will be able to handle some carbs along with some fat. A fat-burning beast will be able to empty glycogen stores through intense exercise, refill those stores, burn whatever dietary fat isn’t stored, and then easily access and oxidize the fat that is stored when it’s needed. It’s not that the fat-burning beast can’t burn glucose – because glucose is toxic in the blood, we’ll always preferentially burn it, store it, or otherwise “handle” it – it’s that he doesn’t depend on it. I’d even suggest that true fat-adaptation will allow someone to eat a higher carb meal or day without derailing the train. Once the fat-burning machinery has been established and programmed, you should be able to effortlessly switch between fuel sources as needed.

There’s really no “fat-adaptation home test kit.” I suppose you could test your respiratory quotient, which is the ratio of carbon dioxide you produce to oxygen you consume. An RQ of 1+ indicates full glucose-burning; an RQ of 0.7 indicates full fat-burning. Somewhere around 0.8 would probably mean you’re fairly well fat-adapted, while something closer to 1 probably means you’re closer to a sugar-burner. The obese have higher RQs. Diabetics have higher RQs. Nighttime eaters have higher RQs (and lower lipid oxidation). What do these groups all have in common? Lower satiety, insistent hunger, impaired beta-oxidation of fat, increased carb cravings and intake – all hallmarks of the sugar-burner.

It’d be great if you could monitor the efficiency of your mitochondria, including the waste products produced by their ATP manufacturing, perhaps with a really, really powerful microscope, but you’d have to know what you were looking for. And besides, although I like to think our “cellular power plants” resemble the power plant from the Simpsons, I’m pretty sure I’d be disappointed by reality.

No, there’s no test to take, no simple thing to measure, no one number to track, no lab to order from your doctor. To find out if you’re fat-adapted, the most effective way is to ask yourself a few basic questions:

  • Can you go three hours without eating? Is skipping a meal an exercise in futility and misery?
  • Do you enjoy steady, even energy throughout the day? Are midday naps pleasurable indulgences, rather than necessary staples?
  • Can you exercise without carb-loading?
  • Have the headaches and brain fuzziness passed?

Yes? Then you’re probably fat-adapted. Welcome to normal human metabolism!

A quick note about ketosis:

Fat-adaption does not necessarily mean ketosis. Ketosis is ketosis. Fat-adaption describes the ability to burn both fat directly via beta-oxidation and glucose via glycolysis, while ketosis describes the use of fat-derived ketone bodies by tissues (like parts of the brain) that normally use glucose. A ketogenic diet “tells” your body that no or very little glucose is available in the environment. The result? “Impaired” glucose tolerance and “physiological” insulin resistance, which sound like negatives but are actually necessary to spare what little glucose exists for use in the brain. On the other hand, a well-constructed, lower-carb (but not full-blown ketogenic) Primal way of eating that leads to weight loss generally improves insulin sensitivity.

That’s it for today, folks. Send along any questions or comments that you have. I’d love to hear from you guys.

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. Sometimes I want to skip meals b/c I am not hungry or I am fat adapted… but I can’t get over psychologically not having 3 meals a day. And I fear other people saying “you’re not eating” or something like that… any other girls have this issue?

    Meagan wrote on July 5th, 2012
  2. The nerdy scientist in me must point out a correction: I would replace respiratory quotient (RQ) with respiratory exchange ratio (RER). RER refers to whole organisms, while RQ refers to isolated mitochondria. RQ would be near impossible to measure in humans (without cutting out pieces of them, homogenizing those pieces, blah blah biology wet lab stuff).
    Also, RQ can never be >1, so you definitely meant to say RER.
    Also, RER can be measured noninvasively. I do it all the time.
    Other than that, great summary!

    Laurent Wada wrote on July 5th, 2012
  3. You are the man, Mark! You have changed my whole outlook on life, nutrition, and exercise.

    JPizzay wrote on July 5th, 2012
  4. Getting started, about 4 weeks in, I have doubled my eggs, meat and fish proteins intake (from being almost vegetarian), increased a bit fat in my cooking and cut in half grains (cereals and bread). I have not lost weight yet (I’m only 15Lbs over) but I have lost some belly fat and gained a little bit of muscles.

    I’m no way eating a pound of bacon in the morning like I could read on one of these threads, when we eat meat, my wife and I each have a half (typical size) grass-fed hormones-free steak with vegetables (sometimes a grass-fed burger on buns) and that is way enough food IMO. I’m pretty sure Groke was not having a pound or two of meat when he fed himself.

    I’m not completely eliminating grains because I find gain-less diet extremely boring; I make my own delicious bread the French way and have a homemade pizza 100% from scratch or a quiche once in a while. Very rarely sweet stuff however such as cookies, cakes and ice cream, never any soda, never any manufactured food that contains corn syrup and MSG an avoid food potentially containing GMO’s.
    For breakfast instead of a half cup of organic cereals in the morning I just have 1/3 cup on organic rice milk to boot my brain up . Later in the morning I have fatty food, I eat a quality boiled egg (from a local farm when I can) and snack on about a 1/3 cup of nuts (walnuts, almonds and Brazil nuts) with a cup of coffee or two and I don’t get that mid morning drop of energy anymore.

    Overall I feel more energized all day and less tired in the evening, but if I grab a beer and snack on crackers or chips, I can feel my energy level crashing within minutes and get bloated.
    Yesterday I went kiteboarding for almost 5 hours non-stop then refueled with a half medium rare grass-fed steak and well oiled (olives) delicious mixed salad (lettuce, carrots, olives, dried tomatoes and a few black beans), and felt great.

    Geo wrote on July 5th, 2012
  5. This makes interesting reading and explains something that I’ve noticed since switching away from sugar – a couple of times when I’ve been busy this week I’ve missed lunch and simply have not noticed it, whereas in the past I would be starving my lunch time ..

    Neil Matthews wrote on July 5th, 2012
  6. I do not eat more whole grains, but this does not mean that if a baker of bread comes out smelling like I will not eat it because I know the problems that brings.
    To lose weight I have removed the binge eating of dried fruit.
    Also a week I started fasting for breakfast (I had tried a few months ago but apparently I was not ready because I’ve eaten at mid-morning), I feel good and go on without hunger until lunchtime (and I realize that often for lunch I eat more to habit than true hunger)

    Sally wrote on July 5th, 2012
  7. Headaches, grumpiness, fear of running out of steam 40 minutes into my workouts… I try to eat as primal as possible, but how do I make the transition?

    Danetta wrote on July 5th, 2012
  8. Considering I skipped meals all my life, I’d say I’m pretty fat adapted. Food was never an issue for me… problem is I’ve lost about 2 kg since going primal and I was already borderline underweight. No amount of weight lifing is helping me gain, and trying to overeat primal carbs has been a disaster of fruit and potato induced sugar rushes and crashes.

    Meh, I’ve decided to accept the fact that I’ll always be a little underweight.

    Wafaa wrote on July 5th, 2012
  9. How do you train your body to be fat adapted? I’ve read the PB and have been eating the primal way for some time but I don’t think I’m fat adapted yet hence still having difficulty at intermittent fasting.

    I’ve also found it difficult completely excluding starchy carbs so I included plantains as my only starchy carbs for no more than one meal a day.

    Are there any special techniques one can use to become fat-adapted and how long does it take?

    Any posts here you can point me to? I’ve searched but can’t find anything with specific guidelines. Thanks.

    George wrote on July 5th, 2012
  10. I’m still in constant awe of the difference fat burning makes to my overall experience of life. When I gave up smoking many years ago, I never experienced that “liberation” feeling people describe, but being fat adapted? Oh man, you just don’t realise how food dominates your life until it stops being the case.

    When I first read your suggestion of fasting “not IF but WHEN”, I know subconsciously I wrote the idea off as not really being for me: I was almost constantly hungry, so the idea of an unplanned fast seemed impossible!

    But sure enough, only the other day I walked six miles in a fasted state to a pub which had a pretty unappetizing menu for a primal eater. So I had a nice glass of water and walked six miles home again without giving it a second thought.

    Utterly liberating – thank you!

    Rachel wrote on July 5th, 2012
  11. Great article. I have been primal for about 2 months now, and for the past 5 days was in the mountains on a trip with friends. We hiked almost daily, and in the morning I would have tea and maybe some jerky or an egg, then we’d go on a 5 or 6 mile round trip hike. I would eat a few nuts or some more dried beef on the trail if my stomach growled, but I did not feel that howling, must-eat-now-or-die hunger, I wasn’t shaky, tired, crabby or anything like that. Coming back to camp for lunch after all that exercise sometimes I wouldn’t even be hungry, and this was a revelation to me. I never knew this was how my body was supposed to feel! It’s such a relief not to feel like I’m being controlled by hunger or planning my day around food, to know that even if I feel hunger, I am not in imminent danger of turning in to a raving b***h.

    Joanne wrote on July 5th, 2012
  12. What is the word of Fat-adapted and BONKING?

    My body is adjusting to a new way of eating and I have noticed that I can cycle longer in a fasted state. But I do not know how far I can go before I hit the wall. I have a 56 mile ride planned Saturday and am afraid to try it without a carb-y dinner on Friday.

    Please HELP. Thanks!

    John wrote on July 5th, 2012
    • If you can, drink a coke on the ride. Seriously, around the half way point. It won’t hurt your paleo. Later.

      dave wrote on July 5th, 2012
      • Come on, you can’t be health concious about your diet and recommend a coke! There’s better sugar than a coke… coke is one of the worst beverage for your health you can have. Not talking about the sugar but all the chemicals and acids it contains. If you need a sugar jolt, make your own lemonade with organic agave sugar or (real) maple syrup, sparkling water and fresh lemon juice. It taste good too.

        Geo wrote on July 6th, 2012
  13. I’m fat adapted. Yup, I’ve adapted to being fat……Joking of course, getting more paleo by the day. Goal weight, 190.

    dave wrote on July 5th, 2012
  14. I’m a sugar-burner. How do you become fat-adapted? I’m assuming it’s possible to switch from one for the other but what do you have to do to get there?

    Kat wrote on July 5th, 2012
    • Read the Primal Blueprint and do what it says.

      Sharon wrote on July 6th, 2012
  15. HOLY HANNAH, I’ve been researching this on my own incessantly. I’ve been 95-100% primal for the last year. I have no problems with it, I love it. I’ve been faithfully doing Crossfit 5-6 days a week for 8 months and I love it. I dont have a thyroid, 1 year on Armour. However, I cannot lose body fat to save my life. I do body comp tests every 6-8 weeks and I’m simply not losing fat. I am gaining muscle though.
    I can’t skip meals, Im hungry and headachey more often than not and rarely get through a day without a nap. PLEASE HELP! IS THE MISSING THYROID THE KEY?! I’m beyond frustrated!!

    Hannah wrote on July 5th, 2012
    • Hannah-Still working on issues myself, and quite frankly, the hormone stuff makes my head spin sometimes! Good for you to be on Armour rather than the usual T4 only/Synthroid crap. That being said, have you checked your other hormone levels? Vit. D? I’m still learning, but my doc and I are working to get my hormones back into balence. We’re starting with cortisol, since mine is at the extreme low end of what CW says is normal. My doc said no use to try and get thyroid fixed until cortisol and ACTH are back up.
      Interesting take-away, she told me that Armour and one other desiccated thyroid med she used to prescribe now have additives like corn and wheat! She’s currently looking into one called naturthroid ( I think) to see if it’s a cleaner version.
      So you might consider checking some other labs, as well as the content of the Armour you’re taking.
      There’s a website run by fellow thyroid patients called Stop The Thyroid Madness (STTM) that has lots of info on it. I’m still slogging through it, and the book of the same name; they are Sometimes a Little over the Top with their adjectives, if you know what I mean, but the info is very interesting. Hope this helps, Hannah. Good luck!

      BJML wrote on July 7th, 2012
    • I’m still new to this way of life, but I found I lost the most weight when following PB fitness. I’m presently in the middle of a trial of a 90 day cycle of p90x and I’m losing less, if at all. So maybe try out dropping the crossfit and following PB fitness. Also, try tinkering with the amount of protein, dairy and fruit you are eating, one at a time to discover if one of these are hindering you.

      Em wrote on July 9th, 2012
  16. I used to be hungry CONSTANTLY! Until I hit 30 I could also eat constantly and not gain, but then came a quick 25 extra lbs.
    It took me seven years of diet/ exercise to finally get to a system that melted lbs without exercise:
    I eat five-six hours each day only. Example: am smoothie of cultured coconut milk, hemp hearts, raw protein powder, kale, frozen berries and green tea. The rest of my eating period is 80%raw fruits and veggies.
    This way of eating allows me to sleep on an empty gi tract so that all of my restorative sleep is just that, no energy towards digestion/storage.
    I haven’t been hungry in months and have lost 30lbs over the last two yrs!

    Mali wrote on July 5th, 2012
  17. I’m pretty certain I’m a fat burner now having switched to low carb 9 months ago and lost 34lb. I prefer to exercise on an empty stomach – preferably first thing in the morning and at least 2 hours after eating. No longer crave carbs and when I tried my first bagel for 6 months last week I no longer liked it. My trouble is chocolate and I have to factor that into my day but certainly for me the hunger and cravings are largely psychological rather than physiological. When I’m bored or tired or stressed I crave sweet things, when I’m busy I can go for hours without thinking of food. Its so hard to separate the physiological hunger from psychological “hunger”.

    Fiona wrote on July 6th, 2012
  18. In correction to the above – I prefer to exercise 12 hours after eating not the 2 hours stated.

    Fiona wrote on July 6th, 2012
  19. Mark,

    Great post! I’ve always felt better energy levels as a fat burner and just in general healthier and less sluggish. Adapting to a more Primal diet and practicing intermittent fasting has definitely helped me make the transition.


    Alykhan - Fitness Breakout wrote on July 6th, 2012
  20. I have been primal since March. Lost approximately 25 lbs of fat and gained about 10 lbs of muscle. I calculated this through charting body weight, tape measurements and Accu-measure pinch test for body fat percentage. It is very important that all of us not to become so fixated on total weight loss alone. This is not a true picture of what is happening to our bodies.

    In addition, the same simple rule applies to the primal lifestyle, “Calories-in versus Calories-out.” If you want to reduce body fat, you must create a deficit!!!! Just because you are a fat-adapted, primal monster, it does not mean you are free to eat 3,000 kCal in one day when your daily requirements are 1800 kCal.

    For me, I use Intermittent Fasting (IF). I know for some, this is a scary concept, but if you desire weight loss, while keeping your muscle, this may be an approach for you. Mark has many posts on IF so I will not go into detail but I will let you know it worked for me. So how do I know I have not lost muscle while IF-ing? I charted my strength increases over the last 4 months. Increase in weight lifted and reps obtained went up 48%! Yes, this is with eating only once every 16 to 24 hours and no, I did not feel like I was starving. As long as I put in the “primal” only food, I had no hunger pains.

    So as they say, proof is in the pudding!

    Kraig wrote on July 6th, 2012
  21. I LOVE this article, but it makes me think I am doing something wrong — I have been primal for 2+ years and I no longer crave refined carbs (I used to have a HUGE sweet tooth). My cravings now include berries, dates, and nut butters, which I limit because I could eat a whole lot of these things. Constant hunger is still an issue though. I am def. hungry every 3 hours. I used to blame my very high activity level, but is this fair to do? Or am I doing something wrong?

    Hannah wrote on July 6th, 2012
  22. Great article, Mark! Thanks for all of your continued efforts to disseminate information like this in a way I can use to talk to my friends. It’s one thing to know all the chemical processes that go on in the body, it’s another to put it down in a way that makes sense to people who don’t, and you’re a master of that.

    Scot wrote on July 6th, 2012
  23. I’ve only been primal for a month, but I’m pretty sure I’m fat-adapted. Four meals in the last three days, one each for the last two days (a big-ass salad) and 24 hours between those; a four hour walk yesterday and a four-mile jog this morning, both before my one meal of the day. I had gone 18 hours without food when I went on my jog, and worked out for 5 minutes in the middle `cause I felt like it. Easy.

    My only source of carbs in the last three days has been vegetables. I suspect I’m in ketosis. I basically did three IFs in a row. Virtually no hunger, definitely no cravings.

    I’ll have a small dinner tonight and a can of semi-primal clam chowder sometime in the next 22 hours or so (potatoes).

    Bill C wrote on July 6th, 2012
  24. Hmm, I meet the fat-burning criteria except for the constant need to nap and the brain fuzziness … oh, that’s right! I have a six month old. Problem identified!

    Emily wrote on July 6th, 2012
    • Lol, me too! When I first began this I kept wondering why my appetite hadn’t been reduced. Then it dawned on me, duh, I’m nursing a little grokling!

      Em wrote on July 9th, 2012
  25. Just finished “The Art and Science of Low Carbohydrate Performance” by Jeff Volek and Stephen Phinney and I too wonder as a previous poster has pointed out if the gap isn’t that tight as suggested in the book. Mark seems to think you can tolerate more carbs and still be a fat burning machine, the book indicates that you have to be at or under 50 grams to achieve optimal fat burning (along with training at or under 65% of your VO2 max). Just began “The Big Book Of Endurance Training and Racing” by Phil Maffetone, will be interesting when I get to the nutrition chapter what Phil’s take on the subject is.

    Mainer wrote on July 6th, 2012
    • I haven’t read Volek’s & Phinney’s books yet, so I don’t know if this is the case, but it sounds like they are counting “net carbs” (total carbs – insoluble fiber) like the Drs. Eades do, rather than total carbs like Mark.

      Apples and oranges when setting your limits.

      Leaf Eating Carnivore wrote on July 6th, 2012
  26. I’m 9 months into Primal and I would say I’m pretty close to being fat-adapted. A year ago, if I ate a meal with too many carbs, I’d be shaking and desperate for food within 30 minutes. Now, I eat 1 or 2 meals a day and rarely get hungry. When I do, I usually feel like I’m running on empty instead of shaky and grouchy.

    So far I’ve lost 32 pounds, a steady 0.8 pounds per week, which is amazing for someone with hypothyroidism. It took about 2 weeks for my bread cravings to go away. I returned to eating a little cheese and ice cream since I didn’t feel any different with/without them. Those are my indulgences. I do use “Paleo” replacements occasionally, for baked goods, but it’s rare.

    Shelli wrote on July 6th, 2012
  27. Perfect timing Mark! I read this today after a couple rare days above 150g of carbs and wondering if those cravings meant I could still be sugar-adapted.

    But tonight, my kids and I went to the greenbelt near our house here in Phoenix to play soccer. They are 6 and 9 years-old so our play often revolves around keep-away and their thinking it’s funny for Daddy to chase the ball as far and long as possible. I went about 20-25 minutes kicking the ball around and having them make me do many sets of 50-80 yard sprints. At the end, I wasn’t very winded and felt incredibly happy and energized. As I put my arms around my sons on the walk home I thought, yep…definitely fat-adapted! 😉

    Dan wrote on July 6th, 2012
  28. “Fat adapted”…”Sugar Burner”?
    I seem to recall Mark saying Metabolic Typing was hogwash and yet he keeps dancing around the same concepts that Metabolic Typing supports. Metabolic Typing definitely supports Primal Blueprint eating for certain types but with even further detail. I love using Marks Cookbooks for clients to see how easy it is to eat whole foods that lean more towards fats and proteins.
    The take away from this post is that everyone is biochemically unique and we need to find what foods and macro nutrient ratios work for each person. No matter what “type” you are, keeping away from processed foods will also keep you away from the doctor.

    Michael wrote on July 6th, 2012
  29. Anybody heard of Roca Labs Formula? I want to know if the stuff really works. I heard it creates a natural gastric bypass effect so that your food intake is cut by half without surgery. I am definitely a sugar burner.

    elise wrote on July 7th, 2012
  30. Just received some lab work back and the urinalysis (UA) showed traces of ketones; the “normal expected value” was supposed to be negative. The remainder of the UA results confirmed that I had a major UTI ( infection), which I had known from the symptoms.
    Now, going over Mark’s list, I think I’m fat adapted-can go long stretches between meals w/ no crankiness, no napping required, have done workouts in a fasting state and felt hungry but fine afterwards, no more brain fog.
    So, here’s my question : are ketones showing up in my urine because I had the UTI, or because I’m fat adapted? ‘Cause if it’s the latter, and you wanted to check if you were fat adapted or not, I know there are urine dipsticks you can use to check and see if you have ketones in your urine and you could just do this at home-no doctor or lab required. Does anyone have any further ideas or info on this? Seems like it might be easier than that the respiratory efficiency test Mark was describing, if it has any validity as a marker for fat adaptation.

    BJML wrote on July 7th, 2012
  31. Mark
    I’m tired hungry and a complete sugar addict. I crave carbs and rarely eat well. I had a gastric bypass 5 years ago, lost 180 pounds, and have gained back almost 100. I’m tired of being overweight and tired of being tired. I loved this article because it describes me to a tee. My question is where do I start. Seriously! I am ready to get my energy, life and fitness back. I am motivated.

    Verl Workman wrote on July 7th, 2012
    • Good luck! It’s a fun journey to start. Go to the start here tab and just start reading and implementing. Consider yourself a science experiment and have fun!

      Em wrote on July 9th, 2012
  32. Hi there,

    I have a few questions I was hoping you knowledgable people could answer for me…

    I’m relatively new to this style of eating (had pulses and whole grains before, but otherwise mostly paleo). I feel like I’m some way down the Fat Adapted road – don’t get hungry between meals so much, can train without carbs etc. but I would like to become fully fat adapted. My questions are these:

    – how to accelerate that process? Just continue as-is (reasonably low carb, high protein, moderate fat) or move towards a higher fat diet?

    – what happens when you eat carbs? I am vegan one day a week – will these additional carbs have any effect on fat-adaption?

    – I do bouts of quite intense exercise, and normally eat carbs (banana or sweet potato) straight afterwards – if I am fat-burning, do I not need to do this, or do I still need to replenish muscle glycogen stores?

    Thank you in advance for any advice you many have!

    Fi wrote on July 7th, 2012
    • Get an oil lamp. Fill it with protein. Try to get it going. Now fill it with coconut oil and watch it burn baby, burn!

      Don’t be afraid of fat. Fat, as we have just demonstrated, is your fuel. Primal is not high protein, it is high fat.

      If your vegan day consists of vegetables and green leafys with olive oil and/or coconut oil, no problems mate. Consider, however, that one way to eat vegan is to – not eat. How about a fast day instead?

      Consider also the possibility that a vegan day is an affectation. You aren’t actually a philosophical vegan and there is no dietary or environmental reason for it. Let it go.

      Unless you are are engaging in multi hour, multi times a day, intense exercise in a competitive environment there is no reason to even think about your glycogen stores. It’s a complete irrelevancy. Your body will manufacture what it demands. From stored fat. While you sleep. “Worry” about getting enough high quality sleep.

      Note that an Ironman is NOT a multi session intense exercise just because it is nominally three events. It is a single moderate effort.

      If you have a psychological need to eat something try a hard boiled egg.

      kfg wrote on July 16th, 2012
  33. Mark and all… At our Center, we test our client’s resting and exercise metabolisms using the New Leaf Metabolism Assessment System. We have found it to be extremely important in determining whether the client is “fat adapted” and to what degree. In fact, it does give you an EXACT RQ value that you speak about in your article above and ultimately tells us what percentage the client burns fat versus sugar while at rest. Then, we design an exercise and weight loss nutrition program to help them improve all aspects of their metabolism and lose excess body fat as well. Thanks for posting this article – it truly describes the “real” issue when it comes to why the general population can’t lose and then maintain their weight.

    Richard Farina wrote on July 7th, 2012
  34. Thanks for this article!I am sugar-addict without any doubt and want to change it.I admit that it might seem really strange, but I don’t know how to do it. Just buy some primal book and start to eat this way? And what book would you suggest? Or should I somhow gradually do it? I would be really grateful if someone would give me a short advice.

    elfriide wrote on July 7th, 2012
    • As someone fairly new to paleo eating, I would recommend just going for it. There’s enough stuff on this site that you could read here and then just try things; I found Mark’s 21 Days book particularly useful because it gave me specific tasks for each day, which kind of got me started.

      DEFINITELY clear the junk out of your pantry; if you have to get dressed and leave the house to acquire a craving food, you can better resist ithan if it’s just down the hall.

      I really like the stuff on this website, the rest of Mark’s books, Loren Cordain’s books, Robb Wolf’s book and It Starts With Food.

      Good luck !

      BJML wrote on July 8th, 2012
  35. Ahhh, thanks. That was just what my brain needed after reading someone’s blog post “Ten Reasons I’m Not Primal/Paleo”.

    “……paleo is a fad with no evidence supporting it……”

    She even adds links to one of Mark’s interviews.

    Next blog entry you see CheesyGal and her grain fed mid-western hubby and think, “Gosh, I’m looking at two fairly big reasons why I eat primal”.

    Keep up the good work and thanks.

    Kenny wrote on July 8th, 2012
    • Millions of years of evolutionary eating: fad diet.

      A few decades of eating according to propagandized by marketing and political concerns: standard diet.

      Sometimes the stupid is so great the only thing you can do is point and giggle.

      kfg wrote on July 16th, 2012
  36. Something to note for people who still consume a fair amount of carbs, like me – if you are feeling constantly hungry, check your water intake. Glycogen stores require as much as 3g of water to store 1g of carbs, so if you are dehydrated all the carbs will leave your body without filling up your glycogen.

    Alex wrote on July 8th, 2012
  37. Great article. The one additional thing I would like to add regarding there is no “fat adaptation home test kit.” You can easily test blood ketone levels (bohb) via an inexpensive blood glucose and ketone monitoring system. I read that measuring one’s blood is more accurate than via a urine sample, so I ordered a testing kit with some blood ketone test strips and watched how my bohb levels are around 2-2.5 mmol after I became fully keno adapted (for me, I define that as <= 50 grams of carbs per day max — usually in the 40s for me). The Volek/Phinney book on LC performance was very beneficial for me. I tend to look at any home test kit like this as more of a validation tool that I am in the general range of being in a keno-adapted state, rather than over-analyzing individual test result strips down to the tenths.

    I have found the benefits of LC to be fabulous. I'm training for my first marathon, and I can wake-up early, no food/breakfast, and go out and run 6-8 miles and not feel tired, shaky, etc., something I could never do when I wasn't LC. Moreover, after I'm done with a long run, I'm not even hungry most of the time, and usually wait a few hours to eat, it's great not having to scarf food down for some supposed window for recovery as well as being really hungry. I know other local keno-adapted long-distance runners who have run 50 milers total totally LC leading up to and including the race, etc.

    chris wrote on July 8th, 2012
    • “I read that measuring one’s blood is more accurate than via a urine sample”

      A point often overlooked is that when one becomes adapted to ketones there will be few, if any, ketones in the urine.

      The reason is simple; you’re using them for fuel!

      kfg wrote on July 16th, 2012
  38. This weekend I went on a bike ride with my elite-road-racer boyfriend and some of his friends – 30 miles in about 2.5 hours – fasted, refusing their offers of Gu every 45 minutes, and finished strong! Later the boyf and I discussed fat adaptation, and he really can’t believe it. He’s definitely one of those people who gets cranky if he doesn’t eat every few hours. Fat adaptation and intermittent fasting come easily to me, but what about people who are so strongly sugar-adapted?

    Alexa wrote on July 9th, 2012
  39. Mark,

    I really like much of what you promote and enjoyed this article as well. Happily I am a fat burner. My biggest problem with Primal living is your belief in evolution. Because of your belief you give not credence to the Creator’s injunction not to eat the unclean foods such as pork and shellfish. To promote them is a disservice to your readers and followers. May I suggest you look at the scientific basis of how Biblically unclean foods digest and how they impact human health? ~Jon

    Jon Frank wrote on July 9th, 2012
  40. Some of you mentioned headaches and brain fog symptoms.

    Sounds like low carb dieting to me.

    Since I’ve increased my natural carb intake (of taro, sweet potatoes, normal potatoes, rice and quinoa) my headaches, muscle aches in the chest, brain fog, mood swings, heart racing, high cholesterol, anxiety, low libido and arrhythmia have stopped!

    Having too few carbs can make you excrete minerals, vital to keep your mental health and heart healthy. So if you’re getting same symptoms I did after going on PB, try increasing natural carb intake, increase mineral intake (potassium, magnesium, selenium, copper) and eat more liver to mitigate any loss of vitamins.

    So safe carbs aren’t evil (only wheat & sugar are evil).

    Sylvia wrote on July 10th, 2012

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