Effect of a Three-Week Adaptation to a Low Carbohydrate/High Fat Diet onMetabolism and Cognitive Performance

摘要

One of the principal metabolic adaptations to endurance training is an increasein the muscle's utilization of fat. This study investigated several components of metabolism during a three-week adaptation to a low (7-9%) carbohydrate/high (73-75%) fat diet (LCD) in man. Metabolic measurement were taken initially on ten healthy male volunteers, ages 19-41, on maintenance exercise program while consuming a standard diet (STD) (50 carbohydrate/35% fat). These measurements were subsequently repeated after 7-11 and 17-21 days on the LCD. Questionnaires were administered on repeat occasions to evaluate food acceptability and subjective symptoms. The metabolic tests included intravenous glucose tolerance tests (GTT), meal response tests (MRT), and glucose/insulin clamps (CLAMP). Blood samples were also taken on several occasions during the STD and LCD periods to asses changes in overnight fasted blood glucose, free fatty acids, triglycerides, insulin, glucagon, total cholesterol, high density lipoprotein (HDL), low density lipoprotein (LDL), cortisol, thyroid hormone, electrolytes, ketone bodies. The LCD was well-tolerated during the three-week adaptation period. The LCD produced lower blood triglycerides (-30%), glucose, thyroid hormone, and insulin/glucagon ratio. The LCD also elevated blood HDL-cholesterol, free fatty acids, and transiently elevated cortisol and beta-OH-butyrate. The MRT demonstrated markedly lower insulin, glucose, and triglyceride concentrations from consuming the LCD. The metabolic adaptation to the LCD resulted in unchanged insulin response to the GTT in the face of higher blood glucose during the test.