KETO DIETS REDUCE ATHLETIC PERFORMANCE!
By Steve Blechman
A ketogenic diet is high in fat, low in protein and low in carbohydrate. The diet promotes the metabolic formation of ketone bodies by causing the body to use fat (rather than carbohydrate) as its main energy source. The ketogenic diet forces the body to burn body fat rather than protein and carbohydrate because of low protein and carbohydrate in the diet. The enhanced fatty acid oxidation in the liver into ketone bodies has been shown to suppress appetite and enhance weight loss. Interest in the ketogenic diet has grown for weight loss and type 2 diabetes (JAMA, January 16, 2018.) A very low-carbohydrate, high-fat ketogenic diet causes the body to switch from burning carbohydrates to burning fat.
The most impressive low-carb study published to date in reference to health and body composition appeared in the journal Circulation in 2017. This diet study used magnetic resonance imaging (MRI) technology for the first time, measuring changes in body and organ fat during 18 months on a Mediterranean/low-carb diet. The Mediterranean low-carb diet was significantly superior to a low-fat diet in decreasing fat storage, including visceral (deep abdominal) liver and heart fat. High visceral fat has been shown to increase metabolic syndrome, inflammation, cardiovascular disease and diabetes. A meta-analysis of 13 randomized controlled trials suggests that people on ketogenic diets tend to lose more weight than people on low-fat diets. In another 12-month weight-loss diet study, there was no significant difference in weight change between a low-fat diet versus a low-carbohydrate diet (JAMA, February 20, 2018).
Unfortunately, ketogenic diets hinder exercise performance. New research from St. Louis University (Journal of Sports Medicine & Physical Fitness, April 2018) found that following low-carbohydrate, ketogenic diets impairs anaerobic exercise performance in exercise trained men and women. Participants did not perform as well during anaerobic exercise in high-intensity, short-duration sports such as sprinting, weightlifting, etc.
“Short-term, low-carbohydrate, ketogenic diets reduce exercise performance in activities that are heavily dependent on an anaerobic energy system,” states Edward P. Weiss, one of the investigators in this new study. “These findings have clear performance implications for athletes, especially for high-intensity, short-duration activities and sports.”
During the Olympics, the media reported that some cyclists were supplementing ketones to improve performance. Ketones produced naturally during metabolism cause euphoria. Cyclists consume ketone supplements to delay fatigue. The brain uses mainly glucose (sugar) for fuel, but it can also use ketones—such as acetone, acetoacetate and beta-hydroxybutyrate (BHB). During low-calorie or low-carbohydrate dieting, the body produces ketones to supply fuels to the brain. A literature review by researchers from Maastricht University, led Philippe Pinckaers, concluded that supplementing ketones has no effect on physical performance. The results are predictable because the breakdown of ketones releases energy more slowly than carbohydrate (Sports Medicine, March, 2017). Also, studies show that ketone supplements, like BHB, turn off stored fat breakdown (lipolysis) through a feedback loop to prevent excessive ketone formation. This creates an inhibition effect, limiting normal ketone production (Journal of Cell Signal, April 13, 2016). There is limited positive scientific research published on BHB and ketones when taken as a dietary supplement for increasing performance in humans. Medium-chained triglycerides (MTC's) are triglycerides with "shorter chain fatty acids known to readily enter the mitochondria and be converted to energy through beta-oxidation" without the requirements of carnitine. Most studies indicate that MTC feeding is ineffective in improving exercise performance, but can increase fat oxidation and energy expenditure. (Journal of the International Society of Sports Nutrition, August 1st, 2018; Int J Food Sci Nutr., Nov 2010).
Low-carb, ketogenic diets are not only detrimental for increasing exercise performance but are also not best for bodybuilding or increasing muscle. This is because ketogenic diets inhibit muscle-sparing activity of mTOR (mechanistic target of rapamycin), causing an increased use of muscle protein for energy— resulting in a loss of muscle and protein synthesis. Activation of mTOR turns on muscle protein synthesis and increases the potential for muscle growth! Ketogenic diets also have a negative impact on other anabolic hormones such as insulin, growth hormone and IGF-1. Also, ketogenic diets create systemic acidosis and lower blood pH, which can impair exercise performance, increase skeletal muscle breakdown and loss of lean muscle mass.
Ketogenic diets could also have a negative effect on blood lipids such as raising LDL (“bad”) cholesterol, because of the high amounts of saturated fats. And some studies have shown that long-term use of high fat, low-carb, ketogenic diets can increase non-alcoholic fatty liver disease (NAFLD), or increased fat deposition in the liver. A review of the literature by researchers from Washington School of Medicine from St. Louis concluded that low-carbohydrate, ketogenic diets contribute to NAFLD. However, short-term consumption has minimal effects on liver function. Anyway, weightlifters consume much more protein in their diet than a ketogenic diet would allow. The level of protein intake that bodybuilders ingest daily would defeat the purpose and take them out of ketosis due to gluconeogenesis in the liver (conversion of protein/amino acids into glucose), raising blood glucose levels.
Ketogenic diets inhibit the most important anabolic hormones for increasing muscle growth (mTOR, insulin, growth hormone and IGF-1). If you want to pack on muscle, ketogenic diets are clearly not for you!
Wroble KA, Trott MN, et al. Low-carbohydrate, ketogenic diet impairs anaerobic exercise performance in exercise-trained women and men: a randomized-sequence crossover trial. J Sports Med Phys Fitness 2018 Apr 04. DOI: 10.23736/S0022-4707.18.08318-4
Abbasi J. Interest in the Ketogenic Diet Grows for Weight Loss and Type 2 Diabetes. JAMA. 2018;319(3):215-217. doi:10.1001/jama.2017.20639
Pinckaers PJM, Churchward-Venne TA, et al. Ketone Bodies and Exercise Performance: The Next Magic Bullet or Merely Hype? Sports Med (2017) 47: 383. https://doi.org/10.1007/s40279-016-0577-y
Leow ZZ, Guelfi KJ, et al. The glycaemic benefits of a very‐low‐carbohydrate ketogenic diet in adults with Type 1 diabetes mellitus may be opposed by increased hypoglycaemia risk and dyslipidaemia. Diabet Med. Accepted Author Manuscript (2018). doi:10.1111/dme.13663
Schugar RC, Crawford PA. Low-carbohydrate ketogenic diets, glucose homeostasis and nonalcoholic fatty liver disease. Curr Opin Clin Nutr Metab Care; 2012 Jul;15(4) 374-380. doi:10.1097/mco.0b013e3283547157. PMID: 22617564; PMCID: PMC3679496.
McDaniel SS, Rensing NR, et al. The ketogenic diet inhibits the mammalian target of rapamycin (mTOR) pathway. Epilepsia 2011;52, e7-11.
Rojas-Morales P, et al. Beta-Hydroxybutyrate: A signaling metabolite in starvation response? Cell Signal 2016; April 13;28(8): 917-923.
Yftach Gepner, Ilan Shelef, Dan Schwarzfuchs, et al. Effect of Distinct Lifestyle Interventions on Mobilization of Fat Storage Pools: The CENTRAL MRI Randomized Controlled Trial. Circulation 2017; CIRCULATION AHA.117.030501, 2017.