Short-term, increasing dietary protein and fat moderately affect energy expenditure, substrate oxidation and uncoupling protein gene expression in rats

Macronutrient composition of diets can influence body-weight development and energy balance. We studied the short-term effects of high-protein (HP) and/or high-fat (HF) diets on energy expenditure (EE) and uncoupling protein (UCP1–3) gene expression. Adult male rats were fed ad libitum with diets containing different protein–fat ratios: adequate protein–normal fat (AP–NF): 20% casein, 5% fat; adequate protein–high fat (AP–HF): 20% casein, 17% fat; high protein–normal fat (HP–NF): 60% casein, 5% fat; high protein–high fat (HP–HF): 60% casein, 17% fat. Wheat starch was used for adjustment of energy content. After 4 days, overnight EE and oxygen consumption, as measured by indirect calorimetry, were higher and body-weight gain was lower in rats fed with HP diets as compared with rats fed diets with adequate protein content ( P