High-intensity exercise and carbohydrate-reduced energy-restricted diet in obese individuals

Continuous high glycemic load and inactivity challenge glucose homeostasis and fat oxidation. Hyperglycemia and high intramuscular glucose levels mediate insulin resistance, a precursor state of type 2 diabetes. The aim was to investigate whether a carbohydrate (CHO)-reduced diet combined with high-intensity interval training (HIIT) enhances the beneficial effects of the diet alone on insulin sensitivity and fat oxidation in obese individuals. Nineteen obese subjects underwent 14 days of CHO-reduced and energy-restricted diet. Ten of them combined the diet with HIIT (4 min bouts at 90% VO2peak up to 10 times, 3 times a week). Oral glucose insulin sensitivity (OGIS) increased significantly in both groups; [diet-exercise (DE) group: pre 377 +/- 70, post 396 +/- 68 mL min(-1) m(-2); diet (D) group: pre 365 +/- 91, post 404 +/- 87 mL min(-1) m(-2); P < 0.001]. Fasting respiratory exchange ratio (RER) decreased significantly in both groups (DE group: pre 0.91 +/- 0.06, post 0.88 +/- 0.06; D group: pre 0.92 +/- 0.07, post 0.86 +/- 0.07; P = 0.002). VO2peak increased significantly in the DE group (pre 27 +/- 5, post 32 +/- 6 mL kg(-1) min(-1); P < 0.001), but not in the D group (pre 26 +/- 9, post 26 +/- 8 mL kg(-1) min(-1)). Lean mass and resistin were preserved only in the DE group (P < 0.05). Fourteen days of CHO-reduced diet improved OGIS and fat oxidation (RER) in obese subjects. The energy-balanced HIIT did not further enhance these parameters, but increased aerobic capacity (VO2peak) and preserved lean mass and resistin.