This study examined the effects of a 15-day isocaloric low carbohydrate (,25% E), high-fat (.50% E) (LCHF) diet on physiological and metabolic alterations in resistance-trained (RT) men. College-aged RT men (n = 11) completed 4 V_ O2max tests using treadmill every 5 days during the 15-day trial. Blood was drawn intravenously pre-exercise across each experimental trial for insulin, cortisol, and glucose. Pulmonary data were collected and substrate oxidation (OXI) was calculated during exercise. Body mass decreased (p , 0.04) with no further changes in anthropometric measures. Time to exhaustion was not affected across each day. Insulin dropped below baseline values (p , 0.0005). Cortisol increased from baseline to day 5 (p , 0.004) but returned back to near baseline at day 10, whereas glucose remained within normal range throughout the duration of the study. Carbohydrate (CHO) OXI dropped (p , 0.001) from baseline to day 5, and fat OXI increased from baseline to day 5 (p , 0.0001). Heart rate decreased from baseline to day 5 (p , 0.001) and again from day 10 to 15 (p , 0.02). Oxygen uptake (V_ O2) decreased from day 5 to 10 (p , 0.0001). A nonketo LCHF diet appears to favor RT men by altering metabolic markers without decrements in aerobic performance and be a potential diet intervention used by coaches. However, the reported cardiorespiratory responses should be interpreted reasonably because of the possibility the subjects running economy improved over experimental trials.
Journal of Strength and Conditioning Research
Waldman, H., Basham, S., Krings, B., Smith, J., Fountain, B., & McAllister, M.
(2018). Effects of a 15-Day Low Carbohydrate, High Fat Diet in Resistance Trained Males. Journal of Strength and Conditioning Research, 32 (11), 3103-3111.