EFFECTS OF A KETOGENIC DIET ON POSTABSORPTIVE AND POSTPRANDIAL HORMONE RESPONSES TO A FAT-RICH MEAL

Abstract

The acute and chronic effects of high levels of dietary fat on postabsorptive and postprandial hormone concentrations have not been examined together in the same study. Eleven healthy men consumed a very-low-carbohydrate ketogenic diet (7% carbohydrate, 28% protein, 65% fat) for eight weeks. Fasting total testosterone (TT), free testosterone (FT), cortisol, and insulin concentrations were determined bi-weekly after a 12 hour overnight fast on two consecutive days. Postprandial hormone responses to a high-fat test meal containing 5.44 MJ (11% carbohydrate, 3% protein, 86% fat) were determined before and after the ketogenic diet. There were no significant changes in fasting hormones during the ketogenic diet. There was a significant reduction one hour after the fat-rich meal for TT (−21.7%) and FT (−23.3%), which remained significantly below baseline for 8 hours after the meal. The postprandial TT and FT responses to the fat-rich meal were not significantly different after the 8-week ketogenic diet. Serum insulin was significantly increased for 2 hours and returned to baseline by 3 hours after the meal. Insulin concentrations were significantly lower before and immediately after the meal following the eight-week ketogenic diet. Serum cortisol concentrations tended to increase immediately after the meal but were significantly below baseline after 1 hour. These data indicate a fat-rich meal results in a prolonged reduction in TT and FT concentrations that is not altered by chronic consumption of a high-fat/low-carbohydrate diet.