According to the Centers for Disease Control and Prevention, from 2017 – 2018, more than 40% of adults in the US were obese. Heart disease, stroke, type 2 diabetes and certain types of cancer are linked to obesity, and these diseases are also some of the leading causes of preventable, premature death.¹ Research has focused on ways to manage the obesity epidemic, and the low-carbohydrate, high-fat ketogenic diet (also known as keto diet) has been proposed as a solution.
Over a century ago, the keto diet was used as a treatment for epilepsy and for children with type 1 diabetes and adults with diabetes due to overweight and obesity, known today as type 2 diabetes.²,³ In recent years, this dietary approach has gained traction primarily for people interested in weight loss.4 The popularity of the keto diet has also enticed athletes to give it a try.
Although there are variations of this diet, the typical macronutrient profile includes carbohydrates being strictly limited to 5-10% of total calorie intake, 55-60% of calories coming from fat and 30-35% of calories from protein.4 The intent of the keto diet is to deplete glycogen stores through the limit on carbohydrate intake, which induces metabolic changes to provide energy to the body through gluconeogenesis and ketogenesis. Gluconeogenesis is the endogenous production of glucose for energy. This happens in the liver where lactic acid, glycerol, and the amino acids alanine and glutamine are enlisted to supply glucose. When glucose becomes less available to the body and gluconeogenesis is not able to keep up with the body’s needs, ketogenesis kicks in to supply the body with energy. During ketogenesis, ketone bodies replace glucose as a primary energy source for the body’s cells containing mitochondria and most importantly, the brain.5
Although more research is needed regarding long-term effects and safety, a well-formulated keto diet can be safe and holds promise for fueling athletic activity as well as helping to manage a range of chronic diseases such as obesity, neurodegenerative disease, cancer and diabetes.4,6
Impact on Sports Performance
The keto diet can be beneficial for helping athletes achieve body mass goals and maintain physical performance, but this diet may not support improvements in ergogenic performance.
A 2021 systematic review of 17 studies examined the impact of the keto diet on performance outcomes of endurance and strength of power athletes. When compared to a control diet of mixed macronutrients, the keto diet did not benefit ergogenic effects of exercise, though it was suggested that physical performance can be maintained. More research is warranted to examine variations due to the diet duration and differences in metabolism due to gender.7
A 2021 systematic review of 10 randomized controlled trials examined the use of a keto diet with less than 10% carbohydrate for endurance athletes. The keto diet was found to be beneficial for respiratory exchange rate (RER), but no significant effect was found on maximal oxygen uptake (VO2 Max), time to exhaustion (TTE), maximal heart rate during exercise (HRmax) and rate of perceived exertion (RPE). Although these findings don’t support a benefit of the keto diet in aerobic capacity or exercise performance of endurance athletes, more high-quality intervention studies on a variety of endurance training programs are needed.8
A 2020 systematic review of 23 studies found that in normal weight people, the keto diet, without calorie restriction, can be used to improve body mass and body fat percentage while maintaining aerobic and anaerobic sports performance. It’s not clear from this review whether this diet provided a benefit for exercise performance, such as an improvement in VO2 Max. This supports the usefulness of the keto diet for helping people reach target body mass without sacrificing athletic performance, and it’s recommended to enlist the help of a healthcare professional to use the keto diet safely and effectively.9
Managing Weight and Chronic Disease
The keto diet can be safe and effective in helping people manage weight and improve health parameters linked to chronic disease, yet further research is needed to determine long-term effects of this eating approach on sustained weight loss and related health improvements.
A 2021 systematic review of 18 studies examining weight, cancer, type 2 diabetes and other chronic diseases found that following the keto diet for a short term (<6 months) might result in greater reduction in body weight (BW), body mass index (BMI), waist circumference (WC), fat mass (FM), fat-free mass (FFM), lean body mass (LBM), visceral adipose tissue (VAT) and percentage body fat (PBF) when compared to a low-fat diet. Medical supervision is advised in using the keto diet for people with serious chronic diseases.10 An examination of 10 studies found no difference between a keto diet and a balanced diet on nutrition parameters including BMI, cholesterol, HDL, LDL and triglyceride levels.11
A very low-calorie diet (VLCD) ≤800 kcal per day is sometimes used along with the keto diet. This calorie level should not be used routinely to manage weight. A systematic review of 13 studies examining the very low-calorie keto diet showed that it was highly effective in reducing body weight, BMI and waist circumference and may be recommended for properly selected patients with appropriate support.12 Ideally, this support should include assessment of the diet to be as nutritionally complete as possible, this calorie level should be followed for no more than 12 weeks and participants should receive ongoing clinical support.13
The Keto Diet & Gut Microbiome
Risk for chronic disease including heart disease, type 2 diabetes and cognitive changes can be linked to inflammation in the digestive tract. A healthy gut microbiome provides many benefits to the body including protection against pathogens, assistance to the immune system, production of healthful short-chain fatty acids (SCFA) and reduced levels of inflammation.14 SCFA support intestinal cells to help strengthen the gut barrier and inhibit the ability of inflammatory compounds, such as lipopolysaccharides (LPS), from alerting the immune system and causing inflammation.14 SCFAs also support ketogenesis, and including leafy greens, vegetables, nuts and small amounts of berries on the keto diet supplies prebiotic fiber to help produce SCFAs.15 Although more and long-term research is needed, a keto diet with plant proteins, such as pea protein, has been shown to support healthy gut microbiota.16
Potential Side Effects
While the potential health benefits are evident, the keto diet is restrictive and can be difficult to sustain due to various side effects, all of which individuals considering a keto diet should be made aware of. Common short-term side effects can include headache, dizziness, constipation, fatigue and other symptoms, and some people experience more severe effects including dehydration and electrolyte disturbances. 4,5,12
Steps for Success on the Keto Diet
Very low carbohydrate diets such as the keto diet can affect diet quality by limiting fruits, vegetables, whole grains and legumes and increasing consumption of animal products. But, with careful planning it is possible to include healthful foods.15 Although the crux of the keto diet is restriction of carbohydrates, non-starchy vegetables should be included as much as possible, as the micronutrients supplied by these vegetables are important for energy metabolism.17 While nutrition tips may vary based on factors such as medical history, here are some tips for healthcare professionals to consider when counseling patients who may be considering a keto diet or are already following one:
- When clients express interest in following a keto diet, healthcare professionals can provide an overview of what to expect on the diet and adjust medications if necessary and under the supervision of a physician.
- Individuals should be encouraged to include non-starchy vegetables, seeds, nuts, avocado and berries, while being mindful of the carbohydrate limit advised by their healthcare provider.18
- Due to urinary excretion of ketone bodies, dehydration is a common early symptom of the keto diet. With this in mind, it’s important to increase water intake to two liters per day and monitor symptoms of low blood pressure such as dizziness, headache and vision changes, increasing sodium intake if necessary. Research on athletes supports the use of 3,000 to 5,000 mg sodium per day to maintain adequate sodium levels as needed.12,19,20,21
- Consider vegetable sources of protein to improve nutritional value of the diet and nut flour to replace wheat products. Orgain’s Keto Plant Protein™ Organic Ketogenic Protein Powder and Organic Plant-Based Protein Pancake & Waffle Mix – Keto-Friendly can help improve the taste and variety of foods and simplify preparation, too. As a bonus, the pea protein can help support a healthy gut microbiome.6
- Analyze the diet for nutritional shortfalls of micronutrients and consider multivitamin and mineral supplementation.
- Address symptoms, such as headache, to ensure compliance. Check in with the client weekly to troubleshoot any other concerns.19
Sports, obesity and chronic diseases require a nutrition plan that can be maintained over time without complications. Although high-quality clinical trials are needed to assess the long-term effects on the body as well as the potential of the keto diet in clinical medicine, the popularity of this popular eating approach demands that healthcare professionals find ways to safely support clients who want to explore its benefits.6
1 The Centers for Disease Control and Prevention. Adult Obesity Facts. Available at: https://www.cdc.gov/obesity/data/adult.html, accessed 1/16/2022.
2 Cooder HR. Epilepsy in Children: With Particular Reference to the Ketogenic Diet. Cal West Med. 1933;39(3):169-173.
3 Henderson G. Court of last appeal – the early history of the high-fat diet for diabetes. J Diabetes Metab 2016;7(8):696.
4 National Center for Biotechnology Information. US National Library of Medicine. StatPearls Publishing. Ketogenic Diet. Masood W, Annamaraju P, Uppaluri KR. Available at: https://www.ncbi.nlm.nih.gov/books/NBK499830/, accessed 1/15/2022.
5 Batch JT, Lamsal SP, Adkins M, Sultan S, Ramirez MN. Advantages and Disadvantages of the Ketogenic Diet: A Review Article. Cureus. 2020;12(8):e9639. Published 2020 Aug 10. doi:10.7759/cureus.9639
6 Ludwig DS. The Ketogenic Diet: Evidence for Optimism but High-Quality Research Needed. J Nutr. 2020;150(6):1354-1359. doi:10.1093/jn/nxz308
7 Murphy NE, Carrigan CT, Margolis LM. High-Fat Ketogenic Diets and Physical Performance: A Systematic Review. Adv Nutr. 2021;12(1):223-233. doi:10.1093/advances/nmaa101
8 Cao J, Lei S, Wang X, Cheng S. The Effect of a Ketogenic Low-Carbohydrate, High-Fat Diet on Aerobic Capacity and Exercise Performance in Endurance Athletes: A Systematic Review and Meta-Analysis. Nutrients. 2021;13(8):2896. Published 2021 Aug 23. doi:10.3390/nu13082896
9 Kang J, Ratamess NA, Faigenbaum AD, Bush JA. Ergogenic Properties of Ketogenic Diets in Normal-Weight Individuals: A Systematic Review. J Am Coll Nutr. 2020;39(7):665-675. doi:10.1080/07315724.2020.1725686
10 Amini MR, Aminianfar A, Naghshi S, Larijani B, Esmaillzadeh A. The effect of ketogenic diet on body composition and anthropometric measures: A systematic review and meta-analysis of randomized controlled trials [published online ahead of print, 2021 Jan 14]. Crit Rev Food Sci Nutr. 2021;1-14. doi:10.1080/10408398.2020.1867957
11 Lopez-Espinoza MA, Chacon-Moscoso S, Sanduvete-Chaves S, Ortega-Maureira MJ, Barrientos-Bravo T. Effect of a Ketogenic Diet on the Nutritional Parameters of Obese Patients: A Systematic Review and Meta-Analysis. Nutrients. 2021;13(9):2946. Published 2021 Aug 25. doi:10.3390/nu13092946
12 Castellana M, Conte E, Cignarelli A, et al. Efficacy and safety of very low-calorie ketogenic diet (VLCKD) in patients with overweight and obesity: A systematic review and meta-analysis. Rev Endocr Metab Disord. 2020;21(1):5-16. doi:10.1007/s11154-019-09514-y
13 Stegenga H, Haines A, Jones K, Wilding J; Guideline Development Group. Identification, assessment, and management of overweight and obesity: summary of updated NICE guidance. BMJ. 2014;349:g6608. Published 2014 Nov 27. doi:10.1136/bmj.g6608
14 Telle-Hansen VH. Holven KB. Ulven SM. Impact of a Healthy Dietary Pattern on GutMicrobiota and Systemic Inflammation in Humans. Nutrients 2018; 10:1783. doi:10.3390/nu10111783
15 Miller VJ, Villamena FA, Volek JS. Nutritional Ketosis and Mitohormesis: Potential Implications for Mitochondrial Function and Human Health. J Nutr Metab. 2018;2018:5157645. Published 2018 Feb 11. doi:10.1155/2018/5157645
16 Paoli A, Mancin L, Bianco A, Thomas E, Mota JF, Piccini F. Ketogenic Diet and Microbiota: Friends or Enemies?. Genes (Basel). 2019;10(7):534. Published 2019 Jul 15. doi:10.3390/genes10070534
17 Crosby L, Davis B, Joshi S, et al. Ketogenic Diets and Chronic Disease: Weighing the Benefits Against the Risks. Front Nutr. 2021;8:702802. Published 2021 Jul 16. doi:10.3389/fnut.2021.702802
18 Dowis K, Banga S. The Potential Health Benefits of the Ketogenic Diet: A Narrative Review. Nutrients. 2021;13(5):1654. Published 2021 May 13. doi:10.3390/nu13051654
19 Griauzde DH, Standafer Lopez K, Saslow LR, Richardson CR. A Pragmatic Approach to Translating Low- and Very Low-Carbohydrate Diets Into Clinical Practice for Patients With Obesity and Type 2 Diabetes. Front Nutr. 2021;8:682137. Published 2021 Jul 19. doi:10.3389/fnut.2021.682137 20 Phinney SD. Ketogenic diets and physical performance. Nutr Metab (Lond). 2004;1(1):2. Published 2004 Aug 17. doi:10.1186/1743-7075-1-2
21 Muscogiuri G, Barrea L, Laudisio D, et al. The management of very low-calorie ketogenic diet in obesity outpatient clinic: a practical guide. J Transl Med. 2019;17(1):356. Published 2019 Oct 29. doi:10.1186/s12967-019-2104-z