Topics » Nutrition Science » Is a High-Fat Diet Healthy? What the Science Says
T. Colin Campbell Center for Nutrition Studies

Variations of the high-fat diet have been popular for decades. Examples include the Atkins Low Carb Diet and numerous takes on the ketogenic diet. Although they are not uniform—there are vegan ketogenic diets, cyclical ketogenic diets, a diet that combines elements of the Mediterranean and ketogenic diets, and many more variations with differing levels of strictness—these diets are generally very high in fat, high in protein, and low in carbohydrate. There may be a marketing rationale for the preferred label, low-carb diet, but we might as well call them high-fat diets because, in order to reduce the intake of carbohydrates to the level considered “healthy” by these diets, the proportion of fat in the diet must by necessity be high.

The T. Colin Campbell Center for Nutrition Studies (CNS) has published a few articles on the ketogenic diet before. If you’re unfamiliar with those resources, I’d encourage you to check them out. Here are just a few titles:

What is the Ketogenic Diet?
Is the Ketogenic Diet Natural for Humans?
Does the Ketogenic Diet Really Work for Weight Loss?

One challenge associated with the high-fat diet that we have not covered as much before, at least not on this site, is how difficult it is for many dieters to follow. When I recently discovered a lifestyle and weight management center close to where I live—affiliated with a very prestigious university, no less—and saw that some of its doctors are advocating for the ketogenic diet, my curiosity got the better of me.[1] I was soon on the website of one of those doctors, which I believe may provide a decent case study to explore the obstacles to adherence.

It can be difficult to find foods that are allowed

The first clue is in the online shop.[2] Apparently, patients were having a difficult time snacking. Too many snacks have carbohydrates. Too many snacks provoke a guilt response in the dieter. To meet this challenge, the good doctor, “developed delicious guilt-free snacks to help make your low-carb lifestyle easier and more sustainable.” That should help.

Another thing that might help is a video on the doctor’s YouTube channel in which he walks you through the store—largely avoiding plant foods; speaking in defense of diet sodas, cheese crisps, eggs, and heavily processed meats (a Group I carcinogen according to the International Agency for Research on Cancer of the WHO[3]); and lamenting the lack of keto-friendly ice cream.[4]

High Fat Diet Myths

There is competing information about what is the “correct” keto diet

I touched on this before: there are many ways to apply yourself to a keto diet. While they are all high in fat and low in carbohydrates, there are various ways to reach those targets. And so there are also various ways to sell the diet. In the video referenced above, the doctor illustrates this fact when looking at several brands of “keto-friendly” ice creams and snack bars, which he dismisses for not being strict enough. He prefers, “that you eat real food,” which of course includes his own snack products.

If you’re looking for a more comprehensive list of foods that are allowed by this particular keto doctor, unfortunately, you’re going to have to pay for it.[5]

And to help us navigate past all of the confusing science we might have heard about carbs and eggs and protein and whole grains and beans and heavily processed meats, the doctor’s business also sells several courses. One of these focuses specifically on overcoming common obstacles to weight loss on a keto diet.[6] This is the course for keto dieters who are at risk of lapsing, and it brings us back to the central question of this article: why would a person on a high-fat diet be at risk of lapsing?

Physical and Emotional Discomfort

The physical discomfort of the diet—which might in the short term include, “headache, fatigue, nausea, dizziness, ‘brain fog,’ gastrointestinal discomfort, decreased energy, feeling faint, and heartbeat alterations,” a smattering of side effects that fall under the general umbrella term of “keto flu”—is only one component of what a keto dieter might feel.[7] There are also familiar emotional reasons, which are conveniently listed in the sales pitch of the course mentioned above:

“you’re stuck… you’re doing everything right but the stubborn weight still won’t budge… you’re confused… you feel frustrated, disappointed, and demoralized… you’re overwhelmed… it’s disheartening to watch other people lose fat… you’re running out of hope that keto will ever work for you.”[8]

Incidentally, in the various descriptions of what the course includes, there are more than 20 direct references to weight loss or fat loss, and not one single passing reference to health or wellness.

It can take a long time to get used to the restrictions of a high-fat diet

The average dieter will require 6–12 months to learn how to follow the ketogenic diet, but how many people will persist during and beyond that learning period? According to a researcher at Louisiana State University, six months is about as long as most people last on a diet, an amount of time that decreases significantly when the plan restricts entire food groups, as in the type of ketogenic diet proposed above.[9]

In a meta-analysis published in the Journal of Clinical Neurology, researchers looked at 12 studies involving adult patients with intractable epilepsy.[10] 270 epileptic patients were evaluated in this meta-analysis, and the researchers compared combined compliance rates for all types of the ketogenic diet, a classical ketogenic diet, and a modified Atkins diet. Because the efficacy of the diet is relatively high for controlling the symptoms experienced by epileptic patients, one might assume that these patients would be highly motivated to comply with the diet. However, even among such patients, the compliance rate for all types of the ketogenic diet was only 45 %. That compliance is defined as following the diet, “up to a given time point, usually the endpoint of each study.” In other words, more than half of these patients—which again, I presume were especially motivated by their condition—did not adhere to the diet for the entirety of their respective studies.

There are limitations to this meta-analysis. As the researchers point out in the discussion section, the total number of patients in the studies included was relatively small. Nevertheless, the findings are consistent with the concerted efforts of keto diet proponents to improve adherence: the second medical provider that specializes in using the keto diet to help patients lose weight at the lifestyle and weight management center referenced above conducts research focused on improving the long-term adherence to the ketogenic diet.[11] Perhaps one way to improve adherence would be to purchase a subscription from Diet Doctor, “the largest low-carb site in the world,” a business that includes this very same doctor on its medical review board and pays him personal fees.[12], [13], [14]

High Fat Diet Myths

It often fails to provide adequate nutrition

As expected, “extreme carbohydrate restriction can profoundly affect diet quality.”[7] Such a diet, “may lack vitamins, minerals, fiber, and phytochemicals… are often low in thiamin, folate, vitamin A, vitamin E, vitamin B6, calcium, magnesium, iron, and potassium… Even when consuming only nutrient-dense foods, a 4:1 ketogenic diet is reported to have multiple micronutrient shortfalls.”

In a 2010 study of popular diet plans, researchers found the Atkins for Life diet plan deficient in 15 of 27 essential micronutrients as per the Reference Daily Intakes (RDIs) determined by the US Food and Drug Administration (FDA).[15] The researchers wanted to know how far off the diet was from providing sufficient levels of those essential micronutrients. What they found is startling: “New calorie intakes were calculated and an evaluation determined that the Atkins for Life diet required 37,500 calories to become 100% RDI sufficient in all 27 essential micronutrients.”

How much food could a person eat before reaching 37,500 calories?

Every year, competitive eaters from around the world arrive on Coney Island to see how many hot dogs and buns they can eat in 10 minutes.[16],[17] The competition this year was televised on ESPN. The winner, it might surprise you to know, did not come as a surprise to anyone in the know. Joey Chestnut (nicknamed Jaws) has won 15 of the last 16 competitions, and this year, with a tally of 63 hot dogs and buns, he defended his title. The hot dog used for the competition (Nathan’s Famous) contains 150 calories, and the average bun is no more than around 150 calories.[18] That means Joey only ate around 18,900 calories. If he wanted to reach 37,500 calories, he would have to eat 125 hot dogs and buns. But of course, if on a ketogenic diet—“Hold the bun, please”—he would actually have to eat around 250 hot dogs.

Far be it from me to question Joey. The man is clearly in a class of his own. But at some point, too much will be too much, even for him. I don’t doubt his tenacity, only his capacity.

Long-Term Success

Because of all the challenges described above, it’s difficult to say with confidence just how impactful, either positively or negatively, this kind of diet is on long-term health. But we know that there are risks associated with consuming high levels of foods containing animal protein,[19][22] and risks associated with yo-yo dieting, which results in rapid weight fluctuation and increased mortality.[23]

This article is not intended to target any one doctor— instead, broader trends that make adherence to a high-fat diet difficult. Many of the same challenges can and do apply to other diets. Dieters of all types can and do face similar challenges. I believe this might have something to do with expectations and the goals motivating the average dieter. It’s obvious from reading about the ketogenic diet and other dieting plans that weight loss is the be-all and end-all for many people. As I alluded to before, there is much less focus on overall health—including emotional health—than on fat loss. And though losing weight is often going to help improve overall health, focusing on weight loss instead of wellness may often be counterproductive. It may even perpetuate many unhealthy eating patterns.

People who are depressed are more likely to be obese, and depressive symptoms are associated with a higher rate of obesity.[24] Moreover, many individuals experience psychological distress, “if they have tried to lose weight in the past and failed to achieve their desired weight.”[25] This is a very dangerous dynamic. A person pinning their hopes on a highly restrictive, nutrient deficient diet that is difficult to adhere to is often going to fall into this vicious trap of feeling like a failure, not because they are a failure, but because the diet’s exploitative salespeople are aggressively marketing products and ideas that fail to sustainably promote health in the long term.


  1. Duke Health. Keto diet for weight management. March 24, 2022. Accessed August 19, 2022.
  2. The official website of dr. eric westman. Products. Accessed August 19, 2022.
  3. Harvard School of Public Health. WHO report says eating processed meat is carcinogenic: understanding the findings. November 3, 2015. Accessed August 19, 2022.
  4. Adapt Your Life. Shopping with dr. westman – dr. eric westman [Video]. YouTube. March 9, 2000. Accessed August 19, 2022.
  5. The official website of dr. eric westman. Page 4. Accessed August 19, 2022.
  6. The official website of dr. eric westman. Courses. Accessed August 19, 2022.
  7. Crosby, L., Davis, B., Joshi, S., Jardine, M., Paul, J., Neola, M., & Barnard, N. D. (2021). Ketogenic Diets and Chronic Disease: Weighing the Benefits Against the Risks. Frontiers in nutrition, 8, 702802.
  8. Adapt Your Life Academy. The stall slayer. Accessed August 19, 2022.!
  9. Zelman, K M. How to Stay on a Diet. Reviewed by Chang L, December 26, 2008. Accessed August 19, 2022.
  10. Ye F, Li XJ, Jiang WL, Sun HB, Liu J. Efficacy of and patient compliance with a ketogenic diet in adults with intractable epilepsy: a meta-analysis. J Clin Neurol. 2015;11(1):26-31. doi:10.3988/jcn.2015.11.1.26
  11. Duke Health. William samuel yancy jr., md, mhs. Accessed August 19, 2022.
  12. Diet Doctor. About diet doctor. Updated by Eenfeldt A, March 23, 2022. Accessed August 19, 2022.
  13. Diet Doctor. Meet our team. Updated by Eenfeldt A, August 12, 2022. Accessed August 19, 2022.
  14. Kumar NK, Merrill JD, Carlson S, German J, Yancy WS Jr. Adherence to Low-Carbohydrate Diets in Patients with Diabetes: A Narrative Review. Diabetes Metab Syndr Obes. 2022;15:477-498. Published 2022 Feb 18. doi:10.2147/DMSO.S292742
  15. Calton J B. Prevalence of micronutrient deficiency in popular diet plans. Journal of the International Society of Sports Nutrition. 2010;7(24). doi:10.1186/1550-2783-7-24
  16. The Athletic. Joey chestnut eats 63 hot dogs to win his 15th nathan’s hot dog eating contest. July 4, 2022. Accessed August 19, 2022.
  17. Dator, J. Everything you need to know about the 2022 nathan’s hot dog eating contest. SB Nation. July 4, 2022. Accessed August 19, 2022.
  18. Hill, A. How many calories are in a hot dog? Healthline. November 22, 2019. Accessed August 19, 2022.
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  20. Armstrong, D. & Doll, R. Environmental factors and cancer incidence and mortality in different countries, with special reference to dietary practices. Int. J. Cancer 15, 617–631 (1975).
  21. Connor, W. E. & Connor, S. L. The key role of nutritional factors in the prevention of coronary heart disease. Prev Med 1, 49–83 (1972).
  22. Jolliffe, N. & Archer, M. Statistical associations between international coronary heart disease death rates and certain environmental factors. J. Chronic Dis. 9, 636–652 (1959).
  23. Harvard Health Publishing. Ketogenic diet: is the ultimate low-carb diet good for you? Harvard Health Blog. August 9, 2022. Accessed August 19, 2022.
  24. Pratt LA, Brody DJ. Depression and obesity in the U.S. adult household population, 2005-2010. NCHS Data Brief. 2014;(167):1-8.
  25. Rand K, Vallis M, Aston M, et al. “It is not the diet; it is the mental part we need help with.” A multilevel analysis of psychological, emotional, and social well-being in obesity. Int J Qual Stud Health Well-being. 2017;12(1):1306421. doi:10.1080/17482631.2017.1306421

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