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Let me introduce myself. My name is Mark Sisson. I’m 63 years young. I live and work in Malibu, California. In a past life I was a professional marathoner and triathlete. Now my life goal is to help 100 million people get healthy. I started this blog in 2006 to empower people to take full responsibility for their own health and enjoyment of life by investigating, discussing, and critically rethinking everything we’ve assumed to be true about health and wellness...

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September 13 2017

Why Am I Getting Low Ketone Readings on a Ketogenic Diet?

By Mark Sisson

Inline_Ketone_Levels_09.13.17Even having finished and printed The Keto Reset, the quest for deeper understanding continues. I keep researching, thinking, revisiting, and discussing the science and practice of ketosis. My writing partner, Brad Kearns, and I maintain a running dialogue on all things keto. The latest conversation revolved around two very common questions or “problems” that keep coming up in the ketogenic community.

Why do some people on a keto diet blow high numbers of ketones while others eating the same way blow low numbers?

and this one…

Is ketosis glycogen-sparing or glycogen-inhibiting?

I won’t offer definitive answers fit to etch into stone. I will offer my exploration of the research, some educated speculation, and actionable advice you can ruminate on. And by all means get back to me with your take on the questions and my explorations, please. Dialogue is essential to understanding.

Why do some people on ketogenic diets produce low ketone readings when they test?

One theory is that some keto-adapted people are so adapted to producing and burning ketones that they don’t leave any extra to spill into the urine and breath. They make only as many as they can use and their cells gobble up almost every ketone they produce. Under this argument, low ketone numbers on a ketogenic diet are a reliable sign of full ketone adaptation.

This sounds plausible, but I haven’t seen any empirical evidence that it’s the case.

Another theory is that the keto-adapted have built so much fat-burning metabolic machinery in their muscles that they can burn free fatty acids directly and don’t require much additional fuel from ketones. They make enough ketones to fuel the brain, since our brain can’t run on fatty acids directly, but your muscles no longer require as many. Many people who have been in long term ketosis can get by quite nicely on 20-30 net grams of carbs a day and might only show .4 or .7 millimolar ketones on a blood test, but they have plenty of energy from burning free fatty acids and maintain muscle mass on relatively fewer calories than when they were dependent on carbs.

Keto pioneers Stephen Phinney and Jeff Volek found that keto dieters blew higher readings early on in the diet when they were still burning ketones in the muscle. As they grew adapted to free fatty acids as a source of fuel and produced ketones primarily for the brain, ketone levels dropped. It was totally normal. If anything, they were more fat/keto-adapted at lower ketone readings.

Consider the energy requirements of the brain. Whether it’s running on glucose (most of the population) or mostly on ketones, the brain is a steady state organ that never spikes energy demand. It’s a slow-burn 24/7 at nearly the same output whether you are sleeping, exercising hard, or concentrating hard. While the brain has a substantial caloric requirement (at roughly 2% of our body weight, it uses 20% of our resting metabolic rate), you don’t need a ton of glucose or ketones at any one time to power your brain gracefully all day long. That’s why people can “get away” with lower ketone production and still reap the benefits we expect from eating this way.

There’s almost certainly a genetic component to ketone production, too. Take the Inuit, who were rarely in ketosis despite traditionally eating a very low-carb diet. It takes several days of deep fasting for them to produce measurable ketones. Yet, they are adept at burning free fatty acids, almost as if they “skip” keto-adaptation and proceed directly to burning fat. Other variants that affect ketone production have yet to be discovered, but they’re out there.

What about people on long term ketogenic diets who still get astronomical readings? What’s going on?

A major factor not often mentioned in whether someone on a keto diet blows high or low ketones is overall calorie intake. How much food are you eating?

Ketones are generated when the amount of dietary fat available to be burned exceeds the supply of oxaloacetate (provided by protein or carbohydrates). It’s not that the body thinks, “This woman needs some ketones, stat.” It’s more like, “I’ve got too much acetyl-COA from all this fat, and I can’t find any oxaloacetate. Guess it’s ketones!”  If you’re the type to use keto to justify chugging olive oil, you’ll generate lots of ketones simply because your fat intake is outpacing the supply of oxaloacetate. Keto athletes eating tons of calories will probably produce more ketones simply because they’re eating so much fat.

If you’ve attained the much-desired “caloric efficiency” I espouse and eating fewer calories overall, you’ll generate fewer ketones but still be “keto.”

Another factor is the use of exogenous ketones. Dean Ornish could take keto esters and blow big numbers.

Above all else, focus on the symptoms.

Can you go without a meal and maintain steady, even energy and concentration?

Are you losing body fat or happy with your body composition?

Are you thinking more clearly?

Has the keto flu come and gone?

Are aerobic activities easier than ever?

If any of those are happening to you, there’s no need to fret over some numbers on a device. The numbers can’t negate your real world experience.

How does ketosis affect glycogen? Does it spare it? Impair our ability to utilize it?

A 1983 study by Steven Phinney gives us a few hints.  He put people on a typical high-carb diet for 4 days, ran a 65% VO2 max endurance test, then switched them over to a ketogenic diet with 20 grams of carbs and about 80-85% of calories from fat for 3 weeks and ran the test again. There was no difference in time to exhaustion after either dietary arm, but glycogen storage and usage changed a ton. During the high-carb arm, the group began the workout with 150 grams of glycogen and ended it with 50 grams. While eating ketogenic, the group began the workout with 75 grams and also ended it with 50 grams.

In a modern setting, the high-carb guy could just squeeze some glucose goo in his mouth, replenish the lost glycogen, and be ready for the next race. But in a setting where glucose goo isn’t available, the keto guy has the advantage. He’s still got 50 grams of glycogen left in the tank—enough for two more races—while the high-carb guy’s 50 grams of carbs will only last him half a race. And the low-carb guy doesn’t have to eat. That’s pretty cool.

It is the modern world. You can grab some glucose goo and win the race. But there’s something special about utilizing the metabolic machinery developed over hundreds of thousands of grueling, blood-and-sweat soaked years.

Sparing glycogen is one thing. Does keto inhibit our ability to utilize the muscle glycogen we’ve spared?

Free fatty acids sure don’t, according to this study. Healthy young males spent a couple hours depleting their muscle glycogen through exercise, after which they were split into two groups. One group got a high-fat breakfast, giving them elevated free fatty acids. One group got a low-fat breakfast, giving them low free fatty acids. They measured glycogen before and after exercise in both groups, as well as markers of the pathway responsible for burning glycogen. Normally, free fatty acids impair glycogen burning. Not this time. Exercise was sufficient to overcome the inhibitory effects of FFA on glycogen-burning.

Semantics enters the fray here. One man’s spared glycogen is another’s inhibited glycogen. We spare glycogen by using less of it—by inhibiting its metabolism. That doesn’t mean the ketogenic athlete can’t burn glycogen when required. It means there’s less to go around, and that’s probably okay because, once again, the ketogenic athlete can do more with fat and ketones and doesn’t need as much glycogen.

Confusing, isn’t it? That’s biology for you.

Still, we know a fair bit. The sparing/inhibiting effect keto has on glycogen metabolism doesn’t impair endurance performance and probably even bolsters it. Long-term elite keto athletes can burn up to 2.3 times more fat at peak oxidation and 59% more fat overall than non-keto athletes, and they do it at higher intensities.

We know fat-adapted athletes beat sugar-burning athletes at high-intensity intervals due to their increased ability to burn fat and retain glycogen. These aren’t 100 m sprints—they’re 4-minute intervals on an incline treadmill—but they’re still glycogen-intensive.

We know low volume, high intensity strength training doesn’t suffer on keto.

What we don’t know is how the delicate balance between glycogen sparing and inhibiting affects high volume, high intensity glycolytic work. I suspect you’re going to lose some performance at the upper echelons of intensity. I also suspect you can regain most, if not all of it by incorporating well-placed carb refeeds.

Anyway, folks, that’s what’s been on my mind these past few days. I wanted to get it out there on the blog so you folks can mull it over and kick it around, and hopefully come back with some good feedback and insight of your own.

Thanks for reading, everybody!


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90 thoughts on “Why Am I Getting Low Ketone Readings on a Ketogenic Diet?”

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  1. One shouldn’t get hung up on ketone numbers alone. Being fat adapted, is far more important…

  2. I read all the keto blog articles with interest, it’s something I’ll probably try one day, but I’m struggling to follow the bit about free fatty acids. This is how my (amateur, no doubt) understanding goes: eat a lot of sugar, burn sugar (glucose). This is where most people are at. Eat rather less sugar and burn fat – but you still need some, even if via gluconeogenesis, for ‘normal’ fat burning (via krebs cycle?) This is the general fat adaptation that primal aims for, right?? Eat so little sugar (and protein) that you can’t even burn fat, then you start making and burning ketones. Am I generally right so far? So… where does the free fatty acid bit come in? What am I missing…

    1. To burn fats, you produce a lot of acetyl CoA, that then feeds in to the Kreb’s cycle. If you have a lot of fat, this step may become limiting. The acetyl CoA will not hang around, but will get processed to ketones to be used elsewhere in the body. Mark says this when he suggests that people who are fat adapted, but glug down the olive oil may blow higher ketones – they have to shunt the acetyl CoA out.

  3. My ketone levels are about in the middle to high range. While perfectly fine with me for now, my doctor seems concerned and wants to retest my levels. (This is from my routine physical.) Any suggestions on explaining Ketosis to a doctor who doesn’t think it is a good thing for anyone?

    1. Your doctor might have reason to be concerned, depending on your various test results and other specifics. He undoubtedly knows more about ketosis than you do, so why not take advantage of what you’re paying him for? Ask him to explain why he doesn’t think it’s a good idea for you.

      1. Never assume a doctor knows anything!! Most of them are quite ignorant on anything beyond what they’re taught in medical school, and that doesn’t include a healthy diet.

      2. ” He undoubtedly knows more about ketosis than you do”

        I hope that was sarcasm Shary. 🙂

        1. Actually any MD should have at least a working knowledge regarding the keto diet. It isn’t rocket science and it’s been around for at least a hundred years. If he doesn’t know about it, then what else doesn’t he know about? In other words, it could be time to find another doctor.

          1. You are absolutely right, they SHOULD know, but unfortunately, on the topic of ketosis, many are sorely lacking. As a matter of fact, I do not think that I have personally ever met a doctor who could correctly explain the difference between nutritional ketosis and ketoacidosis.

        2. I am a nurse and none of the doctors I work with have a clue about This whole ketosis and diet thing. Don’t kid.yourself. I am actually educating them about it some seem interested and some not so much. Not saying that they won’t take an interest now that it’s coming more to the forefront.

          1. Physicians should have learned about the ketogenic diet in medical school and how it was first discovered useful with epileptics.

      1. I agree. Find a doctor who is open to your input and is willing to work with you. Picking a doctor is like choosing a perfume, very personal.

    2. Maybe time for a new doctor i.e. one educated in ancestral health?

      1. Educated in ancestral health? Good luck with that, Matt. I tend to share Linda’s opinion of doctors in general, but most of them should be familiar with a diet used for medical purposes. Whether they think it’s a good idea as a long-term way of life, or for someone not medically in need, is a different story entirely.

    3. Why would a doctor “undoubtedly knows more about ketosis than you do”? It’s more likely a random doctor knows less than a keto-enthusiast who reads MarksDailyApple. “Your waitress undoubtedly knows more about ketosis than you do” sounds silly but it’s no different than saying that about a physician, since physicians do not necessarily have any training about diet and in fact may have a bias against ketosis since they know very likely know about ketoacidosis but not the keto dietary movement.

  4. I’ve had the same experience, low blood ketones, but high readings with the ketonix which indicates I was burning ketones. As soon as I had a day with lots of exercise the blood ketones went up. It turns out that the blood ketones are merely the reserves that the body builds up because it thinks it will need it. If you’re keto adapted, you have optimal levels which you burn hence the low levels in blood ketones.

  5. About testing ketones, mct’s produce bHba which does not show up in a test strip.

  6. The reference to the Inuit is confusing – you already know why they skip ketosis as you alluded to in the boldface preface…because of their genetic mutation.Another problem is that in a 1928 study the Inuit were stated to consume on average 54g of carbs daily in the form of glycogen stored in the meat they eat (

  7. One big reason why some people test low is because they are eating too many carbs to maintain ketosis. This might be due in part to nutritional misunderstandings (“Oh, does that contain carbohydrates? I thought it was a fat.”) and possibly just eating too much. Most foods contain at least a few carbs, and they can add up quickly. You can’t cheat and expect to be in ketosis.

    Persons wanting to try ketosis for medical reasons might do well to obtain an individualized eating plan set up by a nutritional MD or a knowledgeable dietitian versus just winging it. For everyone else, as Mark points out, if you’re happy with the results, don’t worry about the numbers.

  8. Love this stuff, but it all boils down to listening to your body. I really try not to get hung up on numbers anywhere, and focus instead on how I feel and what I can do. I make myself crazy if I track something too closely. I have never tested for ketones, and if I ever do it will be out of curiosity. But I will be the first to admit that eating this way (and I consider myself “borderline” keto) makes me feel amazing. Tons of energy and focus. Comparing old pictures to current ones, I can see that my muscle definition is much better too, and I’m honestly not doing that much. So yeah, keto works, but noooo idea what my readings are.

  9. I never adapted after 2 months. My body fat was at 16% at the start. I saw muscle loss, weight gain and when I finally threw in the towel, the Dexa scan had me at 21.3%! I gained weight even though I was sticking to the macros and keeping my caloric intake at around 1500 cals per day

    1. same thing happened to me…..rarely made it into ketosis, eating only 40 g of carbs, 10% protein and the rest fat. 1600-1800 caloris a day for a month. Felt like crap, no energy, always hungry, my fasting blood sugars went from normal to almost diabetic (125-135 mg/dl). and I gained two pounds. I think people exist along a spectrum of ability to become fat adapted. And i am on the end of spectrum that does not do well with all that fat. Clearly there are undiscovered mutations in many of the hundreds of genes involved in fat metabolism…not the dramatic rare mutations of large effect (like PKU) but more common mutations of small effect that add up to meaningful variations in the ability to metabolize macronutrients.

      I am back to eating a whole foods plant based diet and feel and function much better.
      I am a postmenopausal female BTW.

      1. In some people, high fat diet will lead to physiological insulin resistance; it’s different then insulin resistance in a person who is diabetic. But still, one shouldn’t reach the levels you’ve mentioned. Try changing your ratios, by upping your carbs and protein and dropping your fat intake percentage. Cron-O-meter has a number of ratio options as well as manual override and it’s free, unless you want to generate detailed reports etc.

    2. I think keeping then protein high, which will naturally inhibit ketosis a bit is far more important than being in pure ketosis. I eat way to much protein to really be in full blown ketosis but I do show trace keytones in my system when I test with the pee strips. I think Mark is correct – ketosis is not really the goal, it’s being fat adapted that’s important. For some, that means they will never show ketones in a test.

    3. Flgrl same here! Same problem. Keto doesn’t work for everyone. Certain physiolgies it doesn’t work well with. Every body is different. This or any plan that restricts certain healthy food groups isn’t a long term solution. Keep trying to find what kind of eating works for you. Happy to see im not the only 1 not losing gobs of weight eating gobs of fat LOL

  10. 65 days of Zero Carb diet (meat and water only) and 10 lbs. weight gain! Trying to fast ends in total failure as only after 5 hours without food I feel intense inner cold and moodiness.
    I eat about 2400 cal per day, 70%fat 30% proteins. No breath or urine ketones and only very minimal blood ketones (0.4). Not sure why there is such huge weight gain? Am I or am I not in ketosis?

    Female, 52 y.o. 127 lbs at present.

    1. i’m no expert, but my guess would be that you need a few carbs from green, leafy veggies and healthy fats from sources other than just meat.

      1. Hi Kristen,
        Thank you for your feedback. After plenty of research I learnt that vegetables are not necessary to supply the body’s nutritional needs.

    2. At 127 lbs, 2400 cal/day is way too much… unless you are burning lots of cals like running more than 2 hours a day. Calories still matters in keto. Probably need to be closer to 1400 cal/day.

      1. Thank you, Victor. For a while I started to believe that the “calories in – calories out” theory was old fashionned and false. Now I am not so sure. My weight gain stops when I eat less, but then I also experience hunger.

    3. Your the same age and weight as I am. Even with Keto, calories do still matter if your trying to loose body fat. I suspect your calories are too high. I eat approx. 1500 – 1800 calories for weight maintenance, and I’m about 160cm tall with good muscle tone.

      I would try to cut your calories back to see how you go. Also, a lot can depend on where your at with menopause, so you may still need up to 20g total carbs per day to maintain healthy hormone levels.

      The main thing is to realise that if what your doing isn’t getting the results you’d like, then it’s time to change it and try something different. Experiment is key, as we are all individuals. Good luck 😉

      1. Thank you Amanda, I am not yet ready to throw in the towel but some adjustments are in order and already working. I adjusted my macros and slightly cut down the calories and the gain stopped. I find that I have many wonderful benefits, so consider this experiment succesful and ongoing. 🙂

    4. Read Fat For Fuel by Mercola (also the recent Plant Paradox) book. You should try getting protein under 10% of calories. Protein can be converted into sugar. To verify, you can check blood ketone and blood glucose levels.

      1. Be careful about all this concern lately about protein ‘turning into glucose’. It’s a little more nuanced than it is when someone consumes carbs/sugars which turn into glucose. I cut way down on my protein intake because of some alarmists saying protein turns into glucose and gained weight, felt bad cravings again for carbs and generally didn’t feel I was doing as well. There are a few people addressing this low protein trend and telling people to stop being afraid of protein like we are with carbs. I upped my intake and am losing weight again very steadily and carb cravings are gone again. (see Amy Berger, Ted Naiman, etc. for some deeper info re: protein needs.)

        1. Thank you Tee Dee. I am glad that you figured out what works for you. I don’t have a chance to eat too little proteins as I practice the Zero Carb diet (meat and water only). I have been working on adjusting the macros and eating a little less, and stopped gaining weight.

          1. I eat less than 5g carbs a day, so I’m very close to total carnivore. When I cut back on protein, I had no choice but to increase fat intake for satiety, which is fine in general. I just didn’t like taking in less than 50g protein per day, so I upped it to about 30-40 g per meal…

      2. Thank you, Ben. The information about gluconeogenesis varies and many reserchers disagree on this topic. But it is something I keep my eye on.

    5. .Beata, what on earth are you trying to accomplish? You aren’t doing your health any favors by following such an extreme diet. Get yourself back into a more normal eating pattern that includes a variety of fruit and vegetables, eggs, nuts, etc, Forget about fasting, at least for the time being. Your body is in a state of stress and is probably trying to conserve nutrients. Ketosis doesn’t work well for everyone. Neither does fasting.

    6. A couple thoughts. You may have started this experiment underweight or malnourished, or you may have increased lean mass. You didnt share your height or activities in past 65 days, but this does happen. 127lbs is not a lot of weight to be carrying for your average sized woman.

      1. Thank you, Jay. It is possible that my starting weight of 117 lbs. at 5.4 is not the whole lot. I came to Zero Carb diet from years of calories restriction so yes, it is possible that this had an effect.
        I also had to stop my daily 30 min brisk walks and yoga due to a broken toe, so this may have some sort of effect.

    7. I played a bit with an Atkins style diet a couple decades back. Meat and water., but no exercise All bloating and gas went away, felt great, Gained 3 pounds in 2 weeks, opposite of my goal. Given what’s been learned since then, I think healthy fats were critically missing and my protein intake was too high. (In only 2 weeks I probably wasn’t fat adapted either) Curious if you were using organic/pasture raised meat? Wondering if non-organic non-pasture raised meat can provide fat that contains chemicals that can cause insulin resistance, maybe as a defense mechanism? Anyone know if that’s been researched? It’s known that pigs fed coconuts have a different chemical fat breakdown than when fed other foods.. I had eaten a lot of chicken (no fat) and pork sausage/bacon (neither organic nor pasture raised,) If grains in humans can make us unhealthy, can fat from grain fed animals that we eat counteract keto efforts in certain people?

      1. Jeb, only organic grass fed meat, mostly beef, with some occasional fish. But I think you are right about a different profile of fatty acids in grain fed animals.

  11. I do a lot of exercise and I’ve been doing the Gaps diet for a few years, eating fats and lower carb count and mostly green veggies. I don’t eat starches or grains. i do have perhaps 1 fruit a day occasionally (not everyday). I exercise quite a bit. My concern (although I feel fine) is whether I can burn out my adrenals if I exercise without much carbs at all for a long time.

    I swim three times per week but they are long sessions, I do yoga as often as I can (aim for daily), I do weight training 3 times per week. I walk a lot, cycle here and there, play tennis with a friend etc.

    Thanks Mark for your considered approach and research and science based articles.

    1. You might also want to read Art & Science of Low Carbohydrate Performance ( There are great strategies for athletic performance while ketogenic. I have Crohn’s and exercise a lot, mostly keto, this helped me problem solve some of the longer term issues that came up.

    2. You may want to read The Art and Science of Low Carbohydrate Performance, which gives excellent strategies for athletic performance with keto. I have Crohn’s and mostly keto, and this book has been vital in figuring out how to make auto-immune + keto + athletic performance work

      1. Thank you Josh for your response. I’ll definitely check that out. I’m also doing this because of auto immune tendencies and issues my family members have with auto immune. But I’m also intolerant to many foods and wanted to heal my digestion. I don’t seem to do well with complex carbs anyway so eating more along the Keto diet works better for me but I also dont do too well with eating too many nuts as it affects my digestion so it’s been a balancing act trying to find the foods I can eat to fuel myself. Thanks again

        1. I also can’t really do nuts, soy or dairy, forcing me to get creative. Without getting too detailed…3 things that have changed my life, aside from ketones. 1- Organix comprehensive profile (shows what isn’t working and suggests how to fix) 2- MAP amino supplementation (effective amino use is often an issue with autoimmune causing all kinds of havoc) 3- Aquamin (red algae rich in minerals that I have used in combo with the MAP to restore and build muscle tissue + heal from surgery to spectacular effect under supervision of Stanford Medical). Good luck!

          1. Thanks Joshua. I’ll check all those things out. Just did the 23 and me test and awaiting results. Wanted to see if I have certain genes that might indicate what’s not working but the Organix profile might be much more effective in outlining what I need to do. Thanks so much for taking the time

          2. Thanks Joshua,

            I did the 23 and me test recently and still awaiting results. I was hoping to find some clues in the genes but the Organix profile seems perhaps the better way to go. Thanks for all that. I’ll look at all of that. All the best to you

          3. I really can’t recommend the Organix more. I think everyone should be getting them annually over 35. Game Changer

          4. Thanks you Joshua. I’ve contacted them. Not sure how to go about it from Canada or later in the year Australia so I’ll see if it’s possible.

          5. Hi Josh, Thank you for the link for the online test. There are a few on there do you know which one would be recommended or the difference between them. Thanks for this.

          6. Hi Again Josh,
            As I’m leaving for Australia on October 31st for at least 6 months and haven’t managed to do the organix test I did however buy this amino acid (one bottle)

            I took two with lunch and two with diner. I didn’t really expect to see any difference but I feel amazing. I have energy and I’m calm. I have so much going on around me right now that I have every excuse to be anxious but I’m just peaceful and sleeping well and not worried about little things or even big things. It could be a coincidence (I do yoga) but I think highly unlikely. I would like to do the test and perhaps the link below would work but because I’m leaving I’m pretty sure I should wait until next year. I’m curious. How much do you take? I’m feeling like I should continue to take those supplements

            Thanks so much for your comments here.Feel free to email me directly at if you like.

          7. I am not familiar with that product, but I take about 5g (5 tablets of the MAP aminos). I am not surprised you felt the impact with the free aminos – not having to digest/process them allows your body to just utilize them, something your biology is probably struggling with. Good luck!

          8. Thank you. That’s good. Gives me an idea. I will look at the testing but in the meantime I feel the freeminos or Maps are a good idea! I feel it’s obvious I would have had some deficiency if I’m seeing marked improvements in such a short time.
            Thanks again

      2. 5 years Fat Adapted here, AM ketones .4mmol/l and PM .7mmol/l.Even after a carb tefeed (when i did them) i return to these levels next day. Exercise does elevate them as does fasting but ive never blood tested more than 1.2. I’m always between 10 and 14% body fat and still maintain these nlood ketone ranges even with 130-150g carbs per day (carb tolerance). I think once long term fat adapted, ketones production becomes efficient, muscles utilize FFA or can switch or consecutively burn both Carbs and FFA on demand. I don’t chase Ketones , i chase results.

  12. So… I did the six weeks of Keto to build the “metabolic machinery” . I’ve numbered the symptoms below. Just being fat adapted, just eating primally lets you fast intermittently, so (1) is a gimmie. And intermittent fasting — which I was doing before keto, continued through keto and continue now — loses you body fat. (3) seems to track largely with how well I sleep and i had no experience with (4). Or (5), really. I don’t know if I blew keto altogether or my brain was already living on ketones.

    Is there a useful distinction between being fat adapted and having the “metabolic machinery” from keto?

    (1) Can you go without a meal and maintain steady, even energy and concentration?

    (2) Are you losing body fat or happy with your body composition?

    (3) Are you thinking more clearly?

    (4) Has the keto flu come and gone?

    (5) Are aerobic activities easier than ever?

  13. I eat lots of veggies, get an ample amount of protein via fish and fowl, drink bone broth daily, use olive oil and coconut oil, eat a variety of different nuts, 90% of the small amount of fruit I eat are berries, I avoid simple carbohydrates, and take of host of carefully researched supplements (and eat a couple of Mark’s collagen bars each week). All my meals fall within an 8 hour time period. That’s going to have to do for now, although I admire Mark’s deep dive into biochemistry. I’m focused on epigenetics, autophagy and hormesis these days, and aspects of keto fall into those categories, so good info to file away.

  14. I just read the physical performance chapter in Wilson and Lowery’s “Ketogenic Bible.” They have done some interesting studies. One 11 week study on well trained weight lifters is reported on by Lowery in the current blog of In the eleventh week Carbs were drastically re-introduced into the Keto group’s diet.

    I’m surprised that they didn’t mention your contributions in their “Bible.” I guess that they were just going for peer reviewed, controlled studies. But I think that intelligent insight and interpretation (based on self experiment of N=1 and observations of smany clients, as well as on peer reviewed studies) are just as valuable as the raw studies.

    I hope that you can make friends with these guys, and get some cross fertilization going.

  15. Male 35 6’3″ near 185lbs 44 chest 35 waist AFTER I Lost 60 lbs in the last 7 months being hflc/keto. I definitely have all indications of being keto adapted and an ideal body composition. It happened so fast I couldn’t keep up with it. I went from 38s to 30s. An off the rack 44 to a 38.

    I eat a keto diet VERY high in dairy and vegetables. Moderate protein. I may go through a gallon of heavy whipping cream a week but I focus on nutrient density. I have more digestive issues with kale or broccoli than I do dairy and fat. Lucky me 🙂
    I think I eat something like 2500-3000 calories a day and putting 24 to 48 hours between meals isn’t very difficult or uncommon at this point. Either is having all kinds of energy whether working out or not even fasted.
    I’m in the meanest leanest shape of my life. The keto diet is very weird and seems to work fully backwards from everything you’re not only taught but even intuitively imagine.
    People worry about me even in the face of clearly excellent and rapidly improved health.
    I can’t easily explain it even tho the science makes sense but man do I THRIVE on this diet!

    1. Thanks for sharing. I have always done well on a low-carb ketosis diet but have never stayed at it long enough. Mark’s book and stories like this will help power me through.

  16. This is an appropriate topic for me. For me, I’ve lost over 50 pounds, over the course of about 4 years low carb, about 2 just low carb, then adding in intermittent fasting. I also had shoulder surgery to repair a torn rotator cuff (think no lifting weight >10 pounds for about 6 months, one month in a sling), tried eating resistant starch to see what that was about (about 4 months, no benefit I could see), etc. I got a DEXA scan done, and still could lose another 50+ pounds, though I’d be OK with 20 to 30.

    I gave up on urine strips way back, as they would not show ketosis even when breath and blood did. I don’t use breath as much, only because I have one ketonix, and it gets tiring taking it back and forth from work. I have two meters, so I can test BOHB at home and work.

    There are advocates like Ted Naiman ( who advocate higher protein (and lower calories) even while low carb, the theory being that if you’re trying to lose weight, you would burn fat from your fat stores instead of what you eat. Phinney and Volek have a similar argument.
    The Diet Doctor did a test where he tried upping protein to see if he could kick himself out of ketosis, but he did not:

    The problem for me is that after about 4 years of low carb, I’m rarely in ketosis at all. Last week, for instance, I fasted for about 40 hours, lifted weights at the gym (Body by Science workout), then ate all meat. I had two cups (16 ounces, yes I measure it) black coffee that day. So, my carb content was extremely low, but I ate higher protein, low fat meats. The next morning, my ketones were 0.2 BOHB. And this happens all the time: if I eat higher protein, even with “zero” carb intake (that is, only black coffee and meat), I am not in ketosis. Add some small salad or olives or a pickle, and I’m definitely not in ketosis. The only time I get ketones over or near 1 is if I fast for multiple days, or eat quite high fat.

    Oddly, too, my ketones will go down, especially overnight, while fasting. For instance, I had 0.8 BOHB last night before bed (fasting 24 hours) and had 0.4 this morning (fasting 36 hours). But this doesn’t happen all the time. Sometimes they go up.

    I’m trying to test whether higher protein, lower fat is better for me than higher fat, lower protein, in combination with the intermittent fasting and low carb diets I follow. But if ketones are useless, the only markers I have are blood sugar and insulin. Blood sugar is a bad marker, as the error is plus or minus 15%, and since I have to prick my fingers for this, I get a very inaccurate picture due to so little data. I believe higher protein = lower ketosis and higher blood sugar, but I’m not sure. And even if there is lower ketosis and higher blood sugar, is that bad or good? I find it difficult to tell whether I get hungrier when I eat higher protein, although I think that’s possible. As for insulin, since I have to go have blood drawn for that, I rarely take it.

    Additionally, if I eat something I know will kick me out of ketosis, such as Chicken Shawarma, made in an instant pot and with garlic sauce but with onions and carrots, I find it difficult to tell when I’m back into ketosis. Or even if ketosis is important anymore. It may not be. I’m slowly moving to zero carb/carnivory, as my diet is near 100% meat, with some vegetables every once in a while. But even then, I’m rarely in ketosis.

    For me, the issue is and remains confusing.

    1. I’m not sure why you’re so focused on ketosis. It isn’t a be-all and end-all. It’s just a tool that isn’t always effective. It sounds like your diet has become unbalanced and much too extreme. The human body doesn’t do well on extremes. You might consider moving in the other direction, toward more plant foods and backing off the protein a bit. Normalizing your diet and thereby increasing nutrients may help jumpstart your body’s ability to lose that extra 20 or 30 pounds.

      1. I concur. Though Bob provided a very detailed analysis of his tightly controlled diet and ketosis goals, nothing was mentioned about health and happiness. That’s the goal behind good living isn’t it.- to feel great. Numbers are just that, numbers. Numbers aren’t health or disease.

  17. 1) What is the best way to monitor ketone levels? 2) Can it be done with a regular blog glucose monitor??

  18. One of the issues that I wonder about, and did not notice was addressed in this discussion, is the blood sugar levels in people with low and with higher levels of blood ketones, Also, it seems to me that ketone levels not measured from blood, are very unpredictable. My wife and I have Type II diabetes that has gone away now that we have lost weight and maintain a very low carb diet, even when minimally in a ketotic state. We have found with my wife’s blood tests, being more ketotic than I, that when her blood glucose is 90+, there is no use checking her blood ketones as they will be very low. When she is strict enough on her diet to have blood sugars between 70 and 80, she will find her blood ketones to be between 3 and 6 mmoles. So, just some thoughts here.

  19. For my “sprints”; I run upstairs (100 steps) then rest walking down, then do it again several times. This gets me to my max HR (sometimes above). So am i strictly burning glycogen during these intervals?

  20. I’m 5+ weeks into my keto experiment, and delighted with the results so far. More on the details below, but my question/concern is that my fasting blood glucose numbers (I’m diabetic) have actually increased slightly (averaging about 118), although after eating they have slightly reduced (generally under 130).

    This comes as a surprise since my original goal with keto was lowering my BG, but what I got (and welcome!) was delightful and easy body fat burning, such that I look and feel delightfully slimmer all over in a bathing suit and I’m down 6 pounds, well into my goal range, weight-wise. Even my face is thinner.

    In researching, there’s a theory that the muscles quickly come to prefer keytones as fuel, and spare what little glucose there is for the brain, so it remains in the veins. Ok, fine, but isn’t it causing glycation? Just what I want to avoid.

    I have an A1C test coming up in 2 weeks that will be an interesting view of this keto journey.

    Details:. I’m eating 5% net carbs (less than 20/day, often less than 15), 20% protein, 75% fat, all whole Primal foods, no fake stuff, lots of greens and veggies, no fruit (even berries were a problem, so I have just recently given them up, perhaps this will produce a change in my numbers). Don’t test ketones but have the dragon breath, stinky urine, fat loss, can easily go 24 hours without food, and can Zumba up a storm (after suffering a week-ish of keto-flu weakness, nausea and sleeplessness), sleeping great now. Was Primal 8 years prior so fairly easy conversion to Keto.

    Mark, are my blood glucose increases on keto typical?

  21. I’ve been eating Keto coming up one year as of October 4th.
    I have definitely had an improvement in performance especially in endurance and my musculature seems to have grown also. I maintained crossfit during this time, but have switched to more functional strength training now.
    I’d still like to lose another few percentage points in body fat, but its happening slowly. Ample sleep seems important in this regard.
    I also don’t have so much mental fatigue. Im pretty even except when i need to rest as per normal physiology.
    I test my ketones with breath and blood, but not always, just when i need to fine tune things. Otherwise you can get obsessive about it and there are so many variables apart from what you eat.
    Ive done a few carb refeed cycles early but i just got too interested in carbs again so i stopped that. You don’t need refeeds. I guess you could do them if you were feeling deprived but I don’t eating loads of fat.
    Calories naturally are at about 1500-1900. I struggle to get in 2000.

  22. I’m a 41 year old Master CrossFit athlete, been in keto / LCHF Primal lifestyle for the past 9 years. I feel that my performance has improved a lot and continues to improve pretty significantly. I follow sort of a TKD / CKD where I incorporate weekly carb refeeds (but maybe not enough?) and sometimes eat carbs at night during the week, but never above 60g so It doesn’t even kick me out of ketosis due to activity level. I’ve been playing with some measurements and I noticed that my BG reading after high intensity training sessions is really high (up to 180mg/dl). But it goes down fast (sometimes it goes down to 50mg/dl but I show no side effect of hypo, function completely normal). From my research, the high glucose post high intensity is normal and due to the stressful response of the exercise. But should I try to add some carbs to the post workout window to try to blunt this reaction? Or since its going down so fast it’s nothing to worry about? One more thing that I noticed is that my HR does not move Beyond a certain point. I can still perform quite at a high level and faster than most people at my box but weirdly enough it’s like there’s a block on my HR which doesn’t allow it to move beyond 160 bpm. I’m not sure if this is good or bad! Could I go even faster if my HR would pass this limit?? It is a physiological barrier created by the glycogen sparing mechanism that doesn’t allow my body to move after a certain point so it won’t have to tap into the already low glycogen stores?? I LOVE this lifestyle but at the same time, as athletes; we’re always thinking on how to improve performance. My sport is glycolitic so the question remains: Can we have both keto + performance on CrossFit?!!

  23. I have been eating the “Keto” way for 2 months now and yet I can not get my blood ketone levels above .6 mmols/l. I am eating very few carbs … less than 5% of my diet yet I can not seem to get into the desired 1.3 -1.5 levels. My macros are spot on and I get most of my fat from animal fat as well as MCT and Coconut oils. My weight has gone down very little and I am getting frustrated. Any advice?

    1. I am in the same boat as you are. I have been doing keto for over a year now and no matter what I do, including a three day fast, I cannot get my blood Ketones up more than about .6. Does anyone know why this would be the case? I’ve heard all the comments like you’re eating too many carbs or you’re eating too much protein etc., but when you are water fasting only and it’s exactly the same case, It’s sort of baffling. I’m At the point where I’m thinking some people might just have a body that will not let them go into ketosis. Perhaps their liver just keeps spitting out enough blood sugar to prevent it. At this point I just don’t know. It is really frustrating when you’re doing everything right and it still doesn’t work.

  24. So, had urinalysis done. No ketones!

    This might kind of makes sense now, thank you!

    For years I usually eat one or two meals between 6 and 11. Maybe once or twice a week eat a lunch or brunch.

    Have been eating keto for about 6 months, although always ate plenty of fatty meats, butter evoo etc.
    (With a once or twice a week hoagie or Whopper, lol.

    Could it be that I am pretty used to producing and using ketones efficiently?

    Not overweight, never really have been. Upper body ridiculously lean. I’m female, so carry a little hips, thighs about 2 lbs extra.

  25. About this paragraph “We know fat-adapted athletes beat sugar-burning athletes at high-intensity intervals due to their increased ability to burn fat and retain glycogen.”
    The study that was listed was not of fat adapted athletes in the ketogenic or even low carb sense. It looked at the difference between Well Trained and Recreationally Trained athletes. The Well Trained athletes oxidated fat at a higher rate than the less trained cohort. This was a function of training level not of their dietary selection. There may be a study which shows what the sentence indicates but it wasn’t that study.

  26. I have a ketone question: my bf and I have been doing keto since May 31st. We waited about a month then tested our blood ketone levels. They were around 1.6 and 1.9 respectively. The next week, they jumped to 2.6 and 2.9 and the weight was coming off. I’ve hit a stall and we checked levels tonight. I was 0.7 and he was 1.6. We are eating the same type meals and I even added MCT oil to my daily routine. Can anyone tell me if ketone numbers drop when you become keto adapted or am I back to square one and in just light ketosis. I’m sort of confused. Thanks for any advice

    1. I am reading this because I am fat adapted and in the same situation. I am losing weight though. I think we should just call it normal.

    2. Same story- never did loose inches perhaps maybe at some point when ketones were higher… now no matter what- low fasted 0.5-0.8, and FBG high 5-5.9 mml/L (then it goes down)… basically something is not working fully… apart from that feel really adapted… (food digestion sleep)… is this Insulin resistance pre- keto or developped IR under keto?

  27. Thank you for the article. I’ve been keto for the emotional gains which have been mind blowing and basically “cured” decades of depression.

    However, I was knocked out of ketosis a couple weeks ago and been wavering ever since. Fasting normally helps, but I already have an issue hitting calorie goals. I’ve been hitting the gym to gain muscle as I was underweight from not eating enough for years.

    Basically, I put a ton of focus on protein because I was to gain muscle. As a result, I’ve been testing very low ketones and been struggling with depression. Not nearly as bad, but annoying nonetheless.

    I need to eat more fats. My mindset was fewer carbs = high ketones and great mood. I need to shift to high fat while in ketosis = high ketones and great mood.

    In fact, I’ve been fasting trying to raise my ketones and the foods I have been eating when I do are primarily protein. No wonder I’ve been struggling.

    Thank you 🙂

  28. This article was extremely insightful!

    Thanks a ton??

  29. This is a really excellent article. I appreciate how much you respect empirical information, “the science.” I don’t find that with many articles pertaining to the ketogenic diet. That, or else the writer fails to explain the basis for an opinion/conclusion. I your post because I was searching precisely for a reason as to why my ketone levels have fallen from an average of 2.6 last month, to 1.1 this month, despite no significant changes in my macros (I have only been on this diet for two months.) I think I’ll calm down now as it may actually be a good sign that I’m adapting well. To newbies, it is easy to get frustrated when you’re doing all the right things, yet the numbers are heading down. I’ve bookmarked to website. I’ll be back. Thanks.

  30. Well, I can certainly testify that a ketogenic diet significantly impairs weight training in the 8 to 12 repetition range. It’s such a shame, because I love weight training but I also love the ketogenic diet. Weight training was my preferred form of exercise, and because I’ve not been able to lift as I used to, I think I may also be losing some muscle mass, which is not great for a 41 year old guy who faces increasing sarcopenia.

    Unfortunately there is so little research on targeted ketogenic diet, or cyclic ketogenic diet, or other strategic carb loading protocols that one is left only with the option of experimentation, but there are infinite ways of utilising carbohydrate strategically in a ketogenic diet. Where to start, and at this age one doesn’t want to reinvent the wheel.

    So I am in limbo, paralyzed between the options of carbing up or changing my exercise regime and losing my biggest weapon against sarcopenia. Yet I’ve only been keto for 5 weeks. Perhaps I need to give it a bit longer to ensure maximum adaptation so I can see where I stand. Our understanding of resistance training and high-intensity exercise on a ketogenic diet is still too much so in its infancy for us to have any sure guide. Testimony is the only real data we have, other than a few scattered studies which show only the possibility of maintaining strength but not the protocol which enabled them to maintain strength, and no data on how to increase strength and muscle mass when appearing as far as possible to a ketogenic diet.

    Someone tell me where the two go back to carbs or sacrifice the pleasure I have gained weight training for the last couple of years. Please!!!

  31. Thank you millions for posting this article! I am an athlete and have been wondering for 2 years now, why I cannot go over .5 unless I’m fasting on coffee and MCT oil! I am a woman at 9% body fat, well muscled, and consume a total of 30 grams of carbs but about 80% good fats. I do blood tests, and only hit .5 or even low as .4 on any given day. Once I have my coffee and MCT oil I hit over 1 but then when I eat it goes back to .5 Now I know why!