What is a Keto diet?

A Keto diet is a very high-fat, low-carbohydrate eating plan that forces the body to shift from using glucose to using ketones as a primary fuel. This metabolic state is called ketosis.

What is the typical macronutrient distribution in Keto diets?

Popular Keto diets provide about 5% of calories from carbohydrates, 15-25% of calories from protein and 70-80% of calories from fat.

What are the common claims of Keto proponents?

It is commonly claimed that Keto diets:

  • Improve brain function
  • Improve physical performance
  • Increases longevity
  • Kill cancer cells
  • Produce weight loss
  • Reduce epileptic seizures
  • Reduce cardiovascular disease risk
  • Reverse diabetes

Is there any evidence that Keto diets are effective?

Convincing Evidence

  • Epilepsy – 36-85% of patients with epilepsy experience more than 50% seizure reduction with ketogenic diets; 10-15% become seizure-free. Especially effective for those who do not respond to medications or have rare metabolic disorders.

Moderate Evidence

  • Weight loss – favorable short term results; long term results similar to other weight loss diets. One metabolic ward study reported greater loss of muscle mass with the Keto diet compared to a 50% carbohydrate diet. Keto diets help to suppress appetite.

Limited Evidence

  • Diabetes – short term trials report weight loss, improved glucose control, reduced HbA1c, lower triglycerides, reduced medications; no reversal of insulin resistance.
  • Cancer – several small studies suggest benefit, especially when used with chemo in early disease stages; no evidence of increased survival with advanced cancers; not helpful for all tumors (some grow faster).
  • Brain function – very preliminary evidence suggests possible benefits for APO E4 negative allele Alzheimer’s patients; animal studies suggest benefits to cognitive function.

Contrary Evidence

  • Longevity – no human studies suggest benefits; low carbohydrate diets are consistently associated with increased mortality.
  • Cardiovascular disease (CVD) – children with epilepsy on Keto diets have high CVD risk; Keto diets increase LDL cholesterol; low-carbohydrate diets are strongly associated with increased CVD mortality.
  • Physical performance – despite fat loss, most studies report reduced performance on Keto diets.

What are the potential benefits?

  • Epileptic seizure reduction
  • Reduced energy intakes
  • Weight loss
  • Lower blood sugar
  • Decreased triglycerides; increased HDL

What are the potential risks?

Short Term

  • Constipation
  • Weakness, fatigue
  • Bad breath
  • Muscle cramps
  • Headaches
  • Increased LDL-cholesterol
  • Impaired glucose tolerance
  • Worsening kidney function
  • Reduced athletic performance

Long Term

  • Possible increase in all cause mortality
  • Increased exposure to POPs – metabolic disorders; birth defects
  • Impaired artery function
  • Kidney stones
  • Bone loss
  • Nutrient deficiencies
  • Non-alcoholic fatty liver disease (NAFLD), hepatic steatosis

Why choose a high carbohydrate plant-based over a high fat Keto diet?

Typical high fat, low carbohydrate Keto diets contain significant amounts of potentially pathogenic compounds such as saturated fat, chemical contaminants, products of high temperature cooking, pro-oxidants such as heme iron, and inflammatory compounds such as Neu5Gc (mostly in red meat) and endotoxins (a breakdown product of dead bacteria found mostly in meat). They are devoid of legumes, whole grains and starchy vegetables such as yams and winter squash, and most fruit. These plant foods help maximize our most protective dietary components – fiber, pre-biotics, phytochemicals, antioxidants, anti-inflammatory compounds, and plant sterols and stanols. For optimal health and longevity, pathogenic dietary components must be minimized and protective components maximized. Keto diets fail in this regard. In addition, Keto diets increase the risk of vitamin and mineral deficiencies.

Can a Keto diet be plant-based?

Yes, it is possible to design a plant-based Keto diet, but it is challenging as plants provide about 58-92% of calories as carbohydrates, with the exception of nuts and seeds which provide only about 12% of calories as carbohydrates. Generally, to achieve ketosis, the diet would include an abundance of concentrated fats and oils, plus nuts, seeds, avocados, coconut, and leafy greens and other non-starchy vegetables. For most people, the health advantages of a higher carbohydrate, low fat, whole food, plant-based diet would be significantly greater than that of a high fat plant-based Keto diet.

Selected References

  1. van Berkel AAet al. Cognitive benefits of the ketogenic diet in patients with epilepsy: A systematic overview. Epilepsy Behav. 2018;87:69-77.
  2. Bueno NBet al. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomized controlled trials. Br J Nutr. 2013;110(7):1178-87.
  3. Hall KD, et al. Energy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men. Am J Clin Nutr. 2016;104(2):324-33.
  4. Brouns F. Overweight and diabetes prevention: is a low-carbohydrate-high-fat diet recommendable? Eur J Nutr. 2018;57(4):1301-1312.
  5. Best Diets US News Rankings. https://health.usnews.com/best-diet/best-easy-diets
  6. Gupta L, et al. Ketogenic diet in endocrine disorders: Current perspectives. J Postgrad Med. 2017;63(4):242-251.
  7. Saslow LR, et al. An Online Intervention Comparing a Very Low-Carbohydrate Ketogenic Diet and Lifestyle Recommendations Versus a Plate Method Diet in Overweight Individuals With Type 2 Diabetes: A Randomized Controlled Trial. J Med Internet Res. 2017;19(2):e36.
  8. Numao S, et al. Short-term low carbohydrate/high-fat diet intake increases postprandial plasma glucose and glucagon-like peptide-1 levels during an oral glucose tolerance test in healthy men. Eur J Clin Nutr. 2012;66(8):926-31.
  9. Castañeda-González LM, et al. Effects of low carbohydrate diets on weight and glycemic control among type 2 diabetes individuals: a systemic review of RCT greater than 12 weeks. Nutr Hosp. 2011;26(6):1270-6.
  10. Czyżewska-Majchrzak Ł, et al. The use of low-carbohydrate diet in type 2 diabetes – benefits and risks. Ann Agric Environ Med. 2014;21(2):320-6.
  11. Brouns F. Overweight and diabetes prevention: is a low-carbohydrate-high-fat diet recommendable? Eur J Nutr. 2018;57(4):1301-1312.

12.   Klement RJ. The emerging role of ketogenic diets in cancer treatment. Curr Opin Clin Nutr Metab Care. 2019;22(2):129-134.

  1. Seidelmann SB, et al. Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis. Lancet Public Health. 2018;3(9):e419-e428.
  2. Azevedo de Lima P, et al. Effect of classic ketogenic diet treatment on lipoprotein subfractions in children and adolescents with refractory epilepsy. Nutrition. 2017;33:271-277.
  3. Li S, Flint A, et al. Low carbohydrate diet from plant or animal sources and mortality among myocardial infarction survivors. J Am Heart Assoc. 2014 Sep;3(5):e001169.
  4. Mansoor N, et al. Effects of low-carbohydrate diets v. low-fat diets on body weight and cardiovascular risk factors: a meta-analysis of randomized controlled trials. Br J Nutr. 2016;115(3):466-79.
  5. Kosinski C, Jornayvaz FR. Effects of Ketogenic Diets on Cardiovascular Risk Factors: Evidence from Animal and Human Studies. 2017;9(5). pii: E517.
  6. Noto H, et al. Low-carbohydrate diets and all-cause mortality: a systematic review and meta-analysis of observational studies. PLoS One. 2013;8(1):e55030.

19.   Mazidi M, et al. Lower carbohydrate diets and all-cause and cause-specific mortality: a population-based cohort study and pooling of prospective studies. Eur Heart J. 2019 Apr 19. pii: ehz174.

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