8 Comebacks For Keto Criticisms

keto criticismsIt’s easy to forget how weird we all are.

We spend our days reading this and other health blogs, communing with Primal and keto folks on social media, staying abreast of the nutrition literature, arguing about arcane metabolic minutiae on forums, counting your linoleic acid intake, and you forget that most people don’t know 2% of what you know about diet.

So, when you hear people criticize keto, don’t get exasperated (even if the criticisms are silly). Be ready to respond. And hey, not all criticisms are unfounded. In many cases, wrangling with them will only make you more honest and informed about your diet. Let’s look at some of the more astute keto critiques….

1) Your Brain Needs Glucose, How Do You Even Think?

This isn’t so much wrong as incomplete. Yes, the brain famously needs glucose—but not as much as we’re lead to believe. Once you’re keto-adapted, ketones can provide most of the brain’s energy needs. At max ketone production and adaptation, you’ll still need about 30 grams of glucose for your brain.

Your liver can make about 150 grams of carbohydrates a day from gluconeogenesis, so even if you don’t eat any carbs at all (and you can definitely eat carbs on keto) you’ll still be able to manufacture the requisite 30 grams of glucose.

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2) Don’t You Need Carbs for Energy?

The beauty of keto (and low-carb eating in general) is that it leads to low insulin—both fasting and post-prandial (after meals). When your insulin is low, you’re able to access your stored body fat and liberate it to be burned for energy. Since even the leanest among us carry pounds of body fat, that means you have tens of thousands of calories of clean-burning energy available for liberation at any time.

Once you’re keto-adapted, you’ll most likely find that you have steadier energy than before.

3) How Do You Get Fiber?

Actually, there are plenty of ways to obtain fiber on a ketogenic diet. Many of the best sources of prebiotic fiber—the kind that feed and nourish the good gut bacteria living in your digestive tract—are fairly low in digestible carbohydrates and mesh well with keto. For example:

  • Berries
  • Jicama
  • Onions
  • Garlic
  • Leeks
  • Dandelion greens
  • Green bananas (Yes, a green banana is mostly resistant starch, which your body cannot digest.)
  • Asparagus
  • Broccoli
  • Dark chocolate
  • Almonds and pistachios
  • Mushrooms
  • Avocados

Plenty of fiber in those.

4) How Do You Exercise Without Carbs?

Quite nicely.

There are two primary energy systems used during exercise: aerobic and anaerobic. Aerobic energy relies on fat; anaerobic relies on glucose. The better you are at burning fat, the more work you can do while remaining aerobic. This preserves stored glucose (glycogen) for more intense efforts, increasing your overall energy efficiency. Particularly for endurance training, being keto-adapted allows you to utilize greater amounts of stored body fat for energy and reserve glycogen for when you really need it.

And besides, if you do engage in glycolytic, glucose-intensive training, you can always cycle carbs in and around your workout sessions. Your insulin-sensitive muscles will suck up any glucose you consume as glycogen without affecting your insulin levels or your ability to generate ketones and burn fat.

5) Doesn’t All That Fat Give You Heart Disease?

The vast majority of studies placing people on low-carb, high-fat or ketogenic diets find that markers of heart health improve rather than decline.

In obese adults with type 2 diabetes, a ketogenic diet improved blood lipids and boosted fat loss compared to a low-calorie diet.

In lean, healthy adults without any weight to lose (and who didn’t lose any weight during the course of the diet), total cholesterol went up from 159 to 208 mg/dL and triglycerides fell from 107 to 79 mg/dL. A lipophobic doc might freak out at the rise in TC, but given that the triglycerides dropped, I bet the change reflects a rise in HDL and an overall positive, at worst-neutral effect.

Now, do some people see classically-deleterious changes to their blood lipids? Sure. Anything can happen. We’re all different. I talk more about keto and cholesterol effects here. But the weight of evidence shows that becoming fat-adapted through a keto diet is better for your heart health than not.

6) You’re Just Losing Water Weight, Not Fat

Here’s the truth:

Yes, when you go keto and start shedding glycogen from your liver and your muscles, you lose a lot of water. That’s because every gram of glycogen is stored with 3-4 grams of water. Burn the glycogen and you lose the water along with it.

But this glycogen-and-water loss is a prerequisite for losing “real” weight. It’s a harbinger for fat loss. Once the glycogen runs low, that’s when you start getting into deep ketosis and developing the ability to burn massive amounts of body fat for energy.

7) I Heard the Keto Diet Kills Your Gut Bacteria

Ah, yes, I remember that study. They either fed people a varied diet of fruits, vegetables, grains, legumes, and other foods—or a diet of lunch meat and cheese. Turns out the lunch meat and cheese “keto diet” was bad for the gut biome, increasing gut bacteria linked to obesity and metabolic problems and decreasing gut bacteria linked to health. Of course it was.

A keto diet doesn’t have to consist of bologna and American cheese slices. In fact, it shouldn’t. As I explained in the fiber section, a well-formulated ketogenic diet is full of prebiotic fiber, non-starchy vegetables, and even low-sugar fruit that provide plenty of nourishment for your healthy gut bacteria. What these studies and media stories attack is a caricature of keto, a diet full of processed meat and low quality cheese. They aren’t relevant for someone following a Primal keto diet.

8) Keto Isn’t Sustainable

Well, what do you mean by sustainable?

If you’re talking about the “restrictiveness” of the diet at a personal level, that depends. Sure, you can’t go keto and continue eating Pop Tarts and donuts for breakfast, heaping bowls of pasta for lunch, and fast food burgers (with the bun, at least) and fries with a shake for dinner. But you can eat eggs, bacon, and blackberries for breakfast. You can eat a Big Ass Salad full of a dozen different species of vegetables for lunch. And you can have a ribeye with buttered broccoli for dinner with a glass of wine. I don’t know about you, but that’s a pretty damn sustainable way to eat in my book.

If you’re talking about the environment, and worrying about farting cows or whatever, the evidence is quickly accumulating that properly-raised and managed grazing livestock can sequester more carbon than they emit, revitalize (and even de-desertify) grasslands, and produce more calories-per-unit-of-input than conventional pasture-raising. A large portion of the world’s surface isn’t even suitable for growing crops and is better used for grazing animals. The environmental sustainability of meat-eating is still an open question, but the popular conception of “meat bad, grains good” is completely incorrect and incomplete.

What other keto criticisms have you encountered in the wild? Leave them down below, and thanks for stopping in today, everyone.


Hussain TA, Mathew TC, Dashti AA, Asfar S, Al-zaid N, Dashti HM. Effect of low-calorie versus low-carbohydrate ketogenic diet in type 2 diabetes. Nutrition. 2012;28(10):1016-21.

Phinney SD, Bistrian BR, Wolfe RR, Blackburn GL. The human metabolic response to chronic ketosis without caloric restriction: physical and biochemical adaptation. Metab Clin Exp. 1983;32(8):757-68.

TAGS:  Keto

About the Author

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

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54 thoughts on “8 Comebacks For Keto Criticisms”

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  1. I’ll answer any of the questions about how I stay so thin when they answer “how do you stay so fat”.
    You don’t have to defend yourself. You’re not on trial. Just do the best you can for this life you live. No one gets out alive. I’m just going to leave at a later date.
    I’ve even been reprimanded at work for recommending Keto/Primal lifestyle.
    All I say is “the emperor is nude”.

    1. Hmmm … I have people ask me how I stay so lean, but it’s never been in an accusatory way, but I’m a guy maybe that’s the difference. I tell them I eat a paleo diet (I don’t initially try to go into the nuances of a primal diet unless they are really interested and ask followup questions) do some light weightlifting and body weight exercises and play a little tennis and they may ask questions or else just respond “oh yeah I’ve heard that’s a good diet but I could never give up .” When you say “reprimanded” I hope you just mean ignorant comments from coworkers. I don’t evangelize (except with my nuclear family) but I will answer questions if posed to me, keeping in mind many people don’t really want to change, want responses that fit their narrative, and as Mark noted are woefully uninformed about what a health lifestyle involves and think simple carbs “are part of a nutritional meal” as the cereal makers might frame it LOL.

      1. Guess the web page does not like angled brackets, tries to treat it as HTML so I’ll use parens … sentence was to read “oh yeah I’ve heard that’s a good diet but I could never give up (insert addicting carb food group here)” 🙂

  2. I’ll answer any of the questions about how I stay so thin when they answer “how do you stay so fat”.
    You don’t have to defend yourself. You’re not on trial. Just do the best you can for this life you live. No one gets out alive. I’m just going to leave at a later date.
    I’ve even been reprimanded at work for recommending Keto/Primal lifestyle.
    All I say is “the emperor is nude”.

  3. Mark, LOVE your stuff. I bought your course and with the added grocery samples option! They are awesome! What a value.

    This post is very good. It is easy to lose perspective when we are personally, so deeply-diving ourselves into the world of Keto and nutrition and health.

    And this is something we all need to bear in mind. People NEED what we know, and I feel an obligation, as do you Mark, to spread the word to them if we can.

    Keep up the good work!

    Rob Cook (founder of Keto Frustrations on FB)

  4. I also get the comment that keto is tough on your liver. Personally I have never felt so good being on Keto, but is there any truth to this criticism?

  5. How do you exercise without carbs?

    I have friends that work out and when they are visiting, I just show them. Then they are curious and ask questions. I may not even eat until dinner after the morning, fasted workout. Then maybe a 3 mile little hike in the afternoon. They are shocked into seeing it can be done.

  6. I was having a discussion with a Vegan clinician the other day and I brought up the physics of cellular fuel. Biology consistently takes the most efficient means to accomplish its tasks. Using fat as energy by the mitochondria of the cell requires two LESS steps than sugar. It produces more ATP (energy) and less byproduct. So, it’s more efficient, more energy, and less byproduct. Doesn’t that sound like a primary fuel and not a secondary? He agreed that that makes sense.

  7. I’ve not had to defend it as much as over-compensate for the fact that my friends immediately assume I “can’t” or won’t eat something and they start to plan around it. “Hey, what if we made strawberry shortcake….oh, David couldn’t eat that.” Says who? I might just eat berries with cream. I may decide to allow have a shortcake biscuit into my macros for the day. I “can” eat anything I choose —even if I know it may knock me out of keto for a day. No big deal, I’ll be back in the next day. I rarely talk about my eating choices or plan so while I appreciate that they’re supportive and not telling me to stop (for whatever questionable media message they’ve heard/read), they’ve instead jumped to conclusions about where and what our social group can eat because of thinking they’re working around me (without asking me). I’ve said before that if we go to a great restaurant and I choose a Caesar salad with added protein, I’m happy. I can’t find something anywhere.

    1. Yes!! My experience as well… And it IS easy to find food at ANY restaurant! Even at McDonald’s you can take the burger out of the bun…

    2. LOVE this, David!

      How many times have we all ready that keto will ruin your social life? Well, mine has not slowed down one bit. I still go out for dinners with friends, and have them for drinks around the camp fire. In two years time, there have only been two occasions where there was nothing keto friendly that I could eat. Once at a convention on BBQ night (they sauced everything) but it was in Kansas City, so I ate BBQ and just avoided the grains. The other time was a graduation party where they had pizza and cake, how on Earth did I ever survive 2 hours without eating? I spent my time socializing instead of eating- how anti-social of me (lol)!

      1. Sometimes I peel the good stuff off the pizza crust. It’s easy to do.

    3. This, for sure!!!! It drives me crazy that friends immediately think we can’t go here/there because of the way I eat. Do they have a salad and some meat? I’m happy! I have found I can truly find something anywhere.

  8. I know Keto is fashionable right now, but these are basically the same criticisms people have levied against all low carb diets at least since Atkins.

    My favorite: “You’re Just Losing Water Weight, Not Fat”

    Yes, I was apparently carrying 50lbs of water weight.

    The biggest problem with all of this is people are extremely uneducated about health and nutrition in general. “Carbs = energy” is one of the biggest “everyone knows” nonsense out there.

    At the end of the day, you can read study after study but if you want to know if/how well a particular diet/health lifestyle works you just have to give it a real effort and record the results (that whole science bit). You can make educated guesses, but I know too many people that read too much and just tell me the way things are.

    I still hear the “yeah, and they died at like 20 years old” when talking about Paleolithic eating principles. But “paleo” diets are less about living like a caveman and more about understanding consumption in the framework of our evolution. That was and still is the biggest “ah-ha!” for me. That became the sort of guide to figure out if I should even care about certain studies or techniques.

    With that said, if your diet is working and people see transformations, that leads to generally healthy conversations. In general, as long as you respect other people’s boundaries and don’t get preachy, these are super easy conversations to have.

    About the only people I deal with negatively in terms of health and nutrition are “well-read” know-it-alls who spout off platitudes from news headlines (see #1, 3, 5, 6, and 7) and they tend to be like that about everything anyway. The other issues are members of the Cult of Veganism. But they’re mixing religion with health and nutrition so… it’s not really about science, studies, or facts anyway. (And not all vegans are members of said cult. I think most of you know the difference!)

    I think #8 is probably the biggest talking point I deal with, even among people having success. I don’t really even like Keto outside of short stints and don’t recommend it to most people I talk to. Good old Primal, for me, is so much easier.

  9. My main concern since discovering I’ve got Hashimoto’s which does not respond well to very low carbs, is that keto doesn’t work for everyone and that’s ok. I’m glad it works for so many but any diet is not a blanket approach for every human on the planet. Paleo was a good starting point for me and I learned a lot since starting it, namely that everyone’s biology is different and I tolerate rice and potatoes just fine.

    1. Yes! I have Hashimoto’s, too. Did the AIP diet and lost 30 kilos in 6 months. People stop me in the street to ask. I always tell them that the food pyramid is a lie and that every person has to find their own diet. Mine is Paleo, minus my intolerances, found while doing AIP. I do not try to be low carb, but because of intolerances do go keto naturally from time to time. At any rate, I do very poorly when I eat lots of carbs, even if that’s improving as (I think) my body develops more metabolic flexibility. And I feel great when in keto. After 1 year with this diet, I got normal blood iron results for the 1st time in 10 years (!) and no bad cholesterol. My dr said my blood test was “to envy”. I’m now ready to try intermited fasting. It’s baby steps for me and lots of listening to my body.

      1. That’s awesome! I’ve read a lot about thyroid issues being potentially reversible with diet so I’m cautiously optimistic it may help. I was hoping Mark might chime in with info but I’m sure he’s too busy to keep up with all the comments! Pretty sure I’ve read everything he’s put out regarding thyroid and I haven’t seen any mention of it in relation to keto.

  10. the criticism I read said that it would cause low thyroid function in women if done for more than a few weeks and causes cortisol levels to raise because the body is stressed.

    1. Hi Kathy,
      I think that people DO get stressed if they make the change from an ordinary SAD diet to keto in one fell swoop. I think it works much better if people change their diets SLOWLY. And then there is no stress.

      1. If that was true, then why are children with epilepsy fasted in a hospital before embarking on the keto diet? Instant two day swich-over is a medical proceedure safe for children even.

        1. Childrens bodies arent geared toward healthy reproduction like an adult womens. So it may be that an i stant two day fast then jump into keto is a gentler transition than a women in child bearing years would have.

      2. I agree. Rather than cleaning out the pantry in one hit, it’s often best to taper off the grains by gradually using them up, so you can phase on to a low carb diet, and (most of the time) avoid the dreaded low carb flu.

    2. This is true, I have Hashimoto’s hypothyroidism and one of the things they advise you on is not to go low carb or calorie.

      1. I don’t know, they usually tell diabetics to eat more carbs because they can medicate and tell cancer patients that diet doesn’t matter, in fact sugar is usually a first choice food for cancer patients.

  11. My answer to the “all that fat” criticism is different than the one above. I simply explain that if you are NOT eating all those carbs (which are the biggest source of calories for most people), and are instead eating lots of vegetables and meats, the primary source of your calories is the fat in the meat. And that is why they call it a “high fat” diet. I then go on to explain that I don’t trim off the fat from my meat or the skin from my chicken, I do butter my cooked vegetables, and put oil & vinegar dressing on my salads, and that the fats help you to absorb the vitamins and minerals, but only if their eyes have not already glazed over…

  12. The only thing I consistently hear is that Keto is going to mess up my metabolism. That I can lose weight by doing Keto, but that I will never again be able to eat carbs without blowing up like a balloon.

  13. I get more pity than criticism. “Oh, you poor thing, you can’t have that can you?” “Oh, I am sorry, I should have brought something special for your diet.” or a very condescending “You really can’t just have one?”

    I used to say “It isn’t that I can’t have it, it is that I choose not to.”

    Now I just say “That’s disgusting, throw it away.” … because it is…

    1. Hahaha I love it! Similar to what I tell my toddlers about unhealthy foods. I’m gonna borrow that 🙂

    2. I tell my kids: “that’s not food, it’s a petroleum derivative.” I also tell them that if it does not rot in a few days, it’s not food.

      1. “if it does not rot in a few days, it’s not food.”

        Excellent point. I once did a six-month stint on a sailboat. During the ‘laying in of the stores’, a bag of supermarket bagels fell behind a storage bin. During the boat clean out 6 months later, the bag of bagels was discovered.

        The bagels looked like they had just been purchased…

  14. Most people I know are simply not prepared to not eat processed foods and grain carbs, but they complain about their weight and various health conditions, and hope that just eating less is the answer. They can’t imagine life without muffins, pasta, white bread in all it’s various forms, etc. It’s an addiction for a lot of people. They often comment on how lean I am and wonder how I have so much energy. I don’t push too hard when people ask what I’m doing , I give them the basic concept and if they’re really interested I’ll go into greater detail and even offer to loan them some books to read.
    It’s sad that most people would rather eat crap and feel crap, however it’s the opposite for me, I’ve been Keto for almost six years and look and feel better now at 50 than when I was 40

  15. The sassy comeback version:

    1. Well obviously I am still here and thinking, so what does that tell you about your assumptions?

    2. No, that’s the point.

    3. Green leaves.

    4. Works fine, that’s the point.

    5. Apparently not.

    6. Really? That 30 lbs was all water? Wow!

    7. Can you tell me exactly where you heard that? (This part is so theoretical that the source isn’t likely to be something trustworthy.)

    8. I’m sustaining it just fine. Oh and by the way, next time you go on a diet, I’ll be sure to make you explain it and ask lots of accusatory questions “for your own good.” That’s supportive right?

    But I generally just say “Not all diets work for everyone. You have to find the one that works for you.”

    The response I’ve had that really bothered me was “Eww, fat is disgusting.” Beyond me why anyone would call anything someone else eats “disgusting” right to their face. I wouldn’t even tell a French person that escargot is “disgusting.” Beyond rude.

    1. I’m pretty sure the thing I like most about escargots is the beurre bourguignon (garlic butter)!

  16. How about worries about ketoacidosis? I commonly hear people raise concerns about this. I often find myself explaining that ketoacidosis is not a result of normal, dietary ketosis.

  17. Love this one …well written and VERY helpful – even as a “refresher” for a Keto zealot like me. ?

  18. I typically just challenge them to a fight and when they’re working on a verbal comeback, I hit them with a three punch combination.

    1. Here is a verbal punch. “I prefer to use my fat for energy, not accumulate it.”

  19. A year and a half ago when I went Keto, the folks at work argued with me and told me how bad it was for my health. 8 months in they were telling me how good I was looking, down 85 lbs (@175). Now it seems everybody I talk to are either Keto or Primal.

  20. I agree. Rather than cleaning out the pantry in one hit, it’s often best to taper off the grains by gradually using them up, so you can phase on to a low carb diet, and (most of the time) avoid the dreaded low carb flu.

  21. These days, if I’m asked, I just tell people I’m a meat and veggies girl, with occasion fruit. People seem to be able to understand keto in those terms.

  22. To me keto is a goal not an absolute. I simply say my body does not do well with the dubious chemicals in factory foods. The packaged food industry wants us to crave what is cheap for them to make and store. They don’t care that it makes us sick, fat and malnurished. In that respect, farm/sea to table is essentially simple for most people to understand.

  23. I love this article! You hit all of the objections! We are raising a few dairy cows on a restoration agriculture small farm. We rotate them through paddocks every 2-4 weeks and follow them with our organically fed ducks and chickens. Every has more than enough to eat and we have apple, cherry, peach, apricot, hazelnut, almond, chestnut, pecan and walnut tree growing along with blackberries, raspberries, red currents and strawberries. Quite an ecosystem. It can be done. We have so much grass and we plan to add sheep and meat cows to our group. All organic!

  24. “Keto isn’t sustainable”. I just had a nutritionist at my new gym tell me that when I told her I’d been eating keto. She wanted me to be on a 40% carb macro. Just because I’m too nice to say no, I did her recommended macros. After 2 weeks, I had to go back to low-carb foods because I couldn’t stand the brain fog, the forgetfulness, and increase in my arthritis inflammation. Now that I’ve read these comebacks, I do wonder what she meant by the word “sustainable”.

  25. My husband always says a balanced diet is best or the Mediterranean diet is best. I say yeah even a little bit of poison or the ancestral Italian diet was different to our version of it today. When I’m not around he eats oats and pasta and bread and pizzas. His father suffered from Alzheimers disease. I try to keep his gut healthy with lots of bone broth and good gut bacteria foods but fear he’s working against me.
    His sleep could be a lot better. He is lean and strong at 68 years of age surfing, windsurfing and cycling so maybe I have nothing to worry about.I enjoy a full primal diet and exercise regime.

  26. I was at a lunch with some of my retired coworkers. I ordered a taco salad without the chips. Just meat and pico and cheese plus guacamole. I didn’t forget the sour cream either. My obese friend took one look at the meat and declared I would get gout. Then he tucked into his fried something in a corn shell smothered in beans and rice and some disgusting looking sauce. I just smiled. I’m 71 and can run rings around him over and over again. Sad.