Dear Mark: Does Low-Carb Shorten Lifespan?

For today’s edition of Dear Mark, I’m answering a single, significant question. It concerns the latest “anti-low-carb” study claiming that we’re all killing ourselves by not eating bread. A reader wonders if the study is legit and if we should be worried about eating fewer carbs than “normal” people.

I don’t think we should be concerned, and I’ll explain why in detail. Let’s take a look and break it down.

Hi Mark,

I’m sure you’ve seen this latest study to claim that low-carb diets will kill us all:

Is it legit?

Yes, I’ve seen it.

Where to start?

This study came from Walter Willet, he of the voluminous mustache and unbridled enthusiasm for seed oils.

The most glaring weakness is the way they gathered the data. Over the course of 25 years, participants were asked to accurately report their diet reaching back as far as six years. This is an inherent issue in most nutrition data gathering, so it’s not unique to this study, but come on. Can you remember what you ate 6 years ago? Did your diet change at all, or was it stable enough to encompass with a curt summary?

The characteristics of the participants differed greatly.

Low-carbers were far more likely:

  • To be men—Males have a higher risk of mortality than women.
  • To be diabetic—Diabetes lowers lifespan, especially in the 1980s (when the bulk of the data was collected).
  • To be sedentary—Failure to exercise is a major risk factor for early death, and ill health in general.
  • To smoke cigarettes—Again, this is an elementary variable. Nothing like being able to smoke indoors. Remember smoking sections on airplanes? I do.
  • To eat fewer fruits and vegetables—Carnivory is popular these days, and may work for some, but plants are still good for you and actually complement a low-carb, high-meat diet quite nicely.
  • To be overweight—All else being equal, the fatter you are, the unhealthier you are.

Even if they were able to “control for” all those variables, you can’t control for the overall health and wellness trajectory of a person hellbent on ignoring their personal health. What other unhealthy things are they doing that weren’t captured and accounted for by the researchers?

For instance, alcohol intake. They didn’t look at alcohol intake in this trial. Seriously, search for “alcohol” in the paper and you’ll come up blank. It’s very likely that the low-carbers were drinking more alcohol, as similarly-conducted epidemiological research has found that “carbohydrate intake [is] the first to decrease with increasing alcohol consumption.” (2) Alcohol can take a serious toll on health and lifespan if you aren’t careful with your intake.

Oh, and low-carbers were also more likely to be on a diet. This might be the most crucial variable of all. Who goes on a diet, typically? People who have a health or weight problem. Who doesn’t diet? People who are happy with their health and weight. There are exceptions to this, obviously, but on a population wide scale, these trends emerge. Did the low-carb diet actually reduce health and lifespan, or did the health conditions that prompted the diet in the first place reduce health and lifespan?

Ultimately, this was all based on observational studies and epidemiological data. It can’t establish cause-and-effect, it can only suggest hypotheses and avenues for future research.

Luckily, we have controlled trials that demonstrate the health benefits of low-carb dieting, all of which correspond to better longevity:

You could make the argument that the positive health effects are purely short-term and that in the long run, those benefits turn to negatives. It wouldn’t be a very good argument, though, because we don’t have any indication that it actually happens. If you go reduce carbs or go keto and you lose body fat, gain lean muscle, improve your fasting blood sugar, normalize your lipids, and reduce inflammatory markers, I see no plausible mechanism by which those improvements lead you to an early grave. Do you?

It seems the burden of proof lies in the Willet camp. If the only healthy range of carbohydrate intake is between 50-55%, he would have to show that:

  • No healthy, long-lived cultures or individuals have a carbohydrate intake that strays from the 50-55% range. Anthropological and ethnographical evidence must confirm.
  • The benefits of low-carb diets, established through randomized controlled trials, are illusory and/or transitory, eventually giving way to health decrements that lower lifespan.

That’s a tough one. Hats off if he can pull it off. I doubt he can.

Thanks for writing in. I hope I allayed any concerns you might have had.

Take care, all, and be sure to share down below with your own comments and questions.


1. Seidelmann, Sarah, MD, et al. Dietary Carbohydrate Intake and Mortality. Lancet. 2018. (Online First)

2. Liangpunsakul S. Relationship between alcohol intake and dietary pattern: findings from NHANES III. World J Gastroenterol. 2010;16(32):4055-60.

3. Thorning TK, Raziani F, Bendsen NT, Astrup A, Tholstrup T, Raben A. Diets with high-fat cheese, high-fat meat, or carbohydrate on cardiovascular risk markers in overweight postmenopausal women: a randomized crossover trial. Am J Clin Nutr. 2015;102(3):573-81.

4. Ballard KD, Quann EE, Kupchak BR, et al. Dietary carbohydrate restriction improves insulin sensitivity, blood pressure, microvascular function, and cellular adhesion markers in individuals taking statins. Nutr Res. 2013;33(11):905-12.

5. Rajaie S, Azadbakht L, Saneei P, Khazaei M, Esmaillzadeh A. Comparative effects of carbohydrate versus fat restriction on serum levels of adipocytokines, markers of inflammation, and endothelial function among women with the metabolic syndrome: a randomized cross-over clinical trial. Ann Nutr Metab. 2013;63(1-2):159-67.

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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29 thoughts on “Dear Mark: Does Low-Carb Shorten Lifespan?”

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  1. Keep in mind also that their consideration of “low carb” is 39% of your calories and also that data from individuals who recorded eating around 600 calories a day for years at a time was acceptable input (not sustainable and probably deadly over an extended period of time)

  2. It’s far more than the foods we eat, or don’t eat. It’s how we sleep… it’s how we move… it’s how we avoid dangers (even low-carb compliant dangers lurk like artificial sweeteners & colors, rancid oils, fluoride, excessive wifi, emfs, vaccines, mercury, non-native water, non-native bedding, non-native eating and drinking containers, non-native toiletries, etc)… it’s how we connect with the earth… it’s how we expose ourselves to the elements that shaped our genome (including sun, soil, hot and cold)… it’s the tribal bonds that we form that give us meaning, purpose, love and laughter.

    – Low-carb diets (not keto) can totally shorten lifespan… think subsisting on skinless boneless chicken breast, skim milk and fat-free cans of tuna.

    – Low-carb diets (yes keto) can totally shorten lifespan… think subsisting on fast food hamburger patties and cheese whiz.

    – Low-carb diets (yes keto) can totally extend lifespan… think subsisting on liver, bone marrow, pastured-eggs and wild fish.

    1. Yes, it is far more than the foods we eat – it is the foods we DON’T eat that are far more important to health.

  3. Thanks for laying this out. It’s nice to have this to show people who point to these garbage studies.

  4. Hey Mark,

    as much as I love this blog… you are not very convincing today.

    The study isn’t bad. They controlled a lot of stuff. They did control for diabetes and energy intake (to make sure that low carbers are not dieting?). However, from what I found they did not control for fruit/veggie intake which was the lowest on the low carb high animal diet.

    1. Did they publish the calculations they used to correct for these factors? If not, then the study is not repeatable and hence not science. It may still be of some value (doubtful for other reasons) but it’s impossible to say if these things were really controlled for.

      Also, it seems reasonable that the benefits of a lower percentage of carb consumption are not linear. IOW, if one does not lower carbs enough to reduce hunger and increase fat-burning, then lower carbs might be a net negative, or at least not helpful.

    2. Only one way to be sure – go to the doctor, get some bloodwork and record your health markers. Jump on a high carb diet for a few months, and then re-check your health markers. The savage effects on your health will be worth the sacrifice to contribute to the pool of knowledge for humanity.

      1. It is a complete fallacy that everyone on a high-carb (or higher carb) diet has, or will have adverse health markers. There are spectacularly healthy people all over the carb spectrum, including within the Paleo/Primal community. This reductionist view of diet and health isn’t particularly productive. As many people have pointed out, there are far more variables in the health equation. Oversimplification and polarization makes for better headlines, but isn’t particularly effective at creating behavior change or improving health.

    3. insulin shortens life spans in all organisms, this is fact. So the more carbs you eat the more insulin you produce therefor the shorter lifespan. This man has a sensible balanced approach.

  5. Did they not come to the opposite conclusion of the PURE study, published last year in the Lancet, which claimed that low carb diets extend life?

  6. Another thing that is a hot item on the internet Mark might want to address:

    “A 50-minute German lecture becoming a viral hit on YouTube might sound unusual, but the title of the talk by Karin Michels, the director of the Institute for Prevention and Tumor Epidemiology at the University of Freiburg and a professor at the Harvard TH Chan School of Public Health, has caused a bit of a stir online. … Michels went a step further than to recommend avoiding the foodstuff, saying “coconut oil is pure poison” and “is one of the worst foods you can eat.” “

  7. Cutting a few years off my life in exchange for years of robust health up until my last breath would be worth the trade. I don’t want to live to be 90 if I have to spend 30 pain-filled years at the mercy of the medical industrial complex. “Live long, drop dead!”

  8. More epidemiology confounded by uncontrolled variables. It’s worth a footnote, maybe. But intervention studies are the only thing anyone should really be looking at.

  9. Let’s face it – in the end you’ll be lucky to get out of life alive…

  10. I saw the article about how unhealthy LCHF eating supposedly is. But at the end of the day, even if it was true it would shorten my life I’d still do it because it makes me me so great!! ?? Live on keto tribe!!

  11. I saw this study on my newsfeed and was pretty sure it was going to be today’s topic, even before the Weekend Link Love basically said as much.

    Since going primal/paleo/ancestral/evolutionary (whatever label you want to use), I’ve found it really easy to tune out the noise. I do look at the data on some studies out of curiosity but the reality is, when I considered my consumption in terms of my evolutionary makeup, everything got a lot simpler. Don’t tell me a basic whole foods diet of meat and veggies won’t work for basically everyone. It pretty much will. Everything else is noise.

    Ridding myself of the myth that primitive man lived these short, painful lives was an absolute game changer.

    And the peanut gallery can say what they want about low carb, but whole foods low carb diets just work. I have seen it over and over again at this point. In addition to weight loss, there are almost always other extremely positive side effects.

    I am inherently distrustful of all these long-term studies. “Correcting for variables” is a crapshoot. It just is. You can dress it up in scientific terminology’s best lipstick, but it’s nothing but a guess and more likely a biased one.

    At the end of the day, my weight loss, energy levels, vanishing pain, vanishing ache, increased libido, increased strength, improved blood markers, etc. are far more valuable than any study—whether it seems to be in line with my own observations or not.

    I look forward to the day when health and nutrition is actually science-based because right now it’s mostly an awful mix of corporate indoctrination and very strange religion.

    1. “At the end of the day, my weight loss, energy levels, vanishing pain, vanishing ache, increased libido, increased strength, improved blood markers, etc. are far more valuable than any study…”

      Exactly how I feel! Well said, Joshua.

  12. Remember when eggs were bad for us? and red meat? This is just another one of those short-sighted studies that will be reversed in a few years.

    If the carbs you’re lowering or eliminating are sugars and grain products, you haven’t got a thing to worry about. Unfortunately, there are still a few elements of the dietary research establishment that consider those things valid “food groups”, probably because they themselves can’t comprehend life without them.

  13. I’ll put myself in the camp that we probably can’t just entirely throw the study out. Willet and Co. are highly regarded, but don’t help themselves that back in the day they were pretty solidly in the camp supportive of trans-esterifcation of fats during the margarine days, and we know how that worked out. They and their colleagues may or may not have gotten it right on salt either.

    On the other hand, if we hope to communicate in an effective way the benefits of reducing CHO intake, helping others to understand this study will take some work. Note that it’s not just the study itself, but the tables contained therein that have several other analyses which show a higher risk of mortality when carbohydrate is replaced by animal protein and fat, and reduced risk when CHO is replaced by plant protein and fat. A potentially important factor raised by the authors is that in people who restrict CHO, fruit and vegetable intake can often be quite poor, which could significantly contribute to the observed mortality risk. This really puts a fine point on the whole “put everything you can into that Big Ass Salad”.

    As with so many other things in Nutrition, this is going to cause substantial confusion, and there’s some burden on those reasonable heads to provide the right information and perspective. All the limitations noted in this discussion are very reasonable, but dismissing this study will not do the trick.

    As for me, I’m still reeling from the shock that almost immediately upon embarking upon Primal I’ve had to cut my blood pressure meds in half, blood sugar dramatically improved, loss of rapid hunger cycles, and generally feeling many of the other improvements that so many have experienced.

    Let’s face it, Lancet will continue to hold a very influential position not only for policy makers, but the public as well. Just when I though there might be enough evidence to start to swing the pendulum at the FDA / UDSA / IOM a little bit back in a better direction, this study will enable them to hold on to their moderate / high carb intake position for foreseeable future.

    Bob (a Ph. D in Biochemistry and many, many years working in Nutrition, FWIW)

    1. Hi Robert,

      thanks for your balanced perspective. The study in itself is not “bad science”, even though it does have its limitations (and if you have read to the end, you will have noticed the authors themselves listed some of them). Worse studies than this one have been cited here at MDA in favor of the LC lifestyle.

      In the end, this study doesn’t say anything about the Primal lifestyle. (Even though the researchers certainly could make some interesting statistical tests, because they know what kinds of food the people – probably – ate.) The Low Carb High Plant Protein/Fat people basically ate lots of peanut butter on white bread and chocolate. The Low Carb High Animal Protein/Fat people didn’t eat as many fruits and veggies as the higher carb people. Maybe in the end, it IS more important for longetivity to eat lotsa plants than to have less glycemic load?


      1. That’s likely a really good thought, and one that perhaps could stand even more focus in the Primal / LC eating pattern. The plant materials have to be there, and its got to be in large quantities.

        Reminds me that many vegetarians / vegans can end up having really poor nutrient intakes just because they don’t have the practice of getting enough of different kinds of plants in, and in sufficient quantity. Too restricted, and too little.

        Off to see what veg I haven’t had in a while…

        1. I have yet to encounter any reputable nutritionist, regardless of their biases, who says that eating a wide variety of fruits and vegetables is a BAD idea. No matter what else we do in our pursuit of health and wellness, we need to be pushing the produce!

  14. I was sure you would be coming out with a helpful analysis of this study. Thanks, Mark.

  15. In addition to all the valid points Mark made, I wonder what % of the meat these folks were eating in the 1980’s was grass-fed. Between 0 & 5 % I would guess. While macronutrient content matters a lot, the quality level of the food matters, too.

  16. This study seems like it is looking at people who by chance are eating a low”er” carb, SAD diet, these are not people who chose a low carb lifestyle or Primal/Paleo lifestyle.

    Checking out the appendix is key here and like how an appendicitis kills a person, it kills the validity of this article. Number 1, Mo’ Money = Mo’ Problems! People making 50k + are going to be working harder jobs at over 40 hours per week, which means more responsibility, more stress, less sleep, more smoking, more booze, more caffeine, less socializing, more fast food, less salads, drinking less general fluids (not just less soda), etc.
    Number 2, there’s no determination about how the animal products were prepared, KFC chicken with skin vs baked chicken with skin and all other fast food vs real food examples (which fast food = soybean oil).

    I’m really getting tired of studies telling me that SAD is bad. We know!!!

  17. Hey Mark, your Q & A session is amazing. I appreciate this post. Thanks for answering readers questions and sharing information on shorten lifespan of low carb diet. This kind of post is helpful for many.

  18. This study was flawed as it took low carb to mean below 40% consumption. Low carb should be much lower percentages and hence they have skewed data.