Effects of a 15-Day Low Carbohydrate, High-Fat Diet in Resistance-Trained Men

J Strength Cond Res. 2018 Nov;32(11):3103-3111. doi: 10.1519/JSC.0000000000002282.


Waldman, HS, Krings, BM, Basham, SA, Smith, JW, Fountain, BJ, and McAllister, MJ. Effects of a 15-day low carbohydrate, high-fat diet in resistance-trained men. J Strength Cond Res 32(11): 3103-3111, 2018-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[Combining Dot Above]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[Combining Dot Above]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.

MeSH terms

  • Blood Glucose / analysis
  • Cardiorespiratory Fitness
  • Diet, Carbohydrate-Restricted*
  • Diet, High-Fat*
  • Exercise Test
  • Heart Rate
  • Humans
  • Hydrocortisone / blood
  • Insulin / blood
  • Male
  • Oxidation-Reduction
  • Oxygen Consumption*
  • Resistance Training
  • Running / physiology*
  • Sports Nutritional Physiological Phenomena*
  • Young Adult


  • Blood Glucose
  • Insulin
  • Hydrocortisone