Functional Protein In Keto-adapted Marathon Runners - A 6-month Randomised Controlled Trial

Evidence of the benefits of a keto low carbohydrate high fat diet (KLCHF) on athletic endurance performance appeared over 40 years ago1. Most studies exploring LCKD in endurance athletes however, have restricted intervention periods from a few days to 2–3 weeks2 thereby limiting understanding of KLCHF diet effects on body composition beyond the initial diet adaptation phase. Adapting to a KLCHF diet reduces fluid retention and stored glycogen in the short term that likely contributes to reductions in body weight observed in many previous studies. Decrements in lean mass are believed to be associated with a loss of functional muscle protein with negative implications for performance. PURPOSE: To compare changes in body composition between well-trained recreational marathon runners over 6-month adaptation to a KLCHF diet v usual high carbohydrate diet in an RCT design. METHODS: We used a simplified and validated3 4-compartment body composition model to calculate functional protein in runners (n = 9) consuming a KLCHF diet (CHO < 20 g per day) and controls runners (n = 8, CHO > 220 g per day) over 6 months. Functional protein was assessed using estimates of bone mineral, fat and lean mass from DXA with total body water measured using Bioelectrical Impedance. RESULTS: Compared to controls, the KLCHF group had significantly reduced body weight (REML: - 4.54 kg), lean mass (-2.51 kg), and fat mass (-2.03 kg) however, no difference in total body water or functional protein from baseline to 6-months. CONCLUSION: Marathon runners assigned to a KLCHF diet for 6-months experienced reduced body weight without compromising functional protein capacity.1.Phinney SD, Bistrian BR, Evans WJ, Gervino E, Blackburn GL. The human metabolic response to chronic ketosis without caloric restriction: preservation of submaximal exercise capability with reduced carbohydrate oxidation. Metabolism. 1983;32(8):769–76.2.Bailey CP, and Hennessy E. A review of the ketogenic diet for endurance athletes: performance enhancer or placebo effect? J Int Soc Sports Nutr. 2020;17:33. 3.Ng BK, Liu YE, Wang W, Kelly TL, Wilson KE, Schoeller DA, Heymsfield SB, and Shepherd JA. Validation of rapid 4-component body composition assessment with the use of dual-energy X-ray absorptiometry and bioelectrical impedance analysis. Am J Clin Nutr. 2018;108:708–715.