The effects of chronic ethanol consumption on energy balance in rats

It remains unclear how ethanol truly impacts body weight and energy balance. Dietary intake studies suggest that energy intake is greater in ethanol consumers; however, large population studies have shown that ethanol intake is in fact not associated with increased body weight. Energy expenditure (EE) has been shown to be either mildly increased or unchanged after acute ethanol intake, but the effects of chronic ethanol intake on energy balance have not been well studied. The following study was performed to prospectively examine the effects of chronic moderate ethanol consumption and its interactions with the macronutrient composition of the diet on energy balance. Male Sprague-Dawley rats (n = 16) were first randomized to either a low-fat diet (LF = 10% fat, 70% carbohydrate, 20% protein) or a high-fat diet (HF = 30% fat, 50% carbohydrate, 20% protein). Rats were then randomized to receive either a 5% ethanol solution (ethanol) or water (control) as their drinking supply (day 14) for a total of 4 groups (LF-ethanol, LF-control, HF-ethanol, HF-control; n = 4 per group). On days 7, 21, and 42, indirect calorimetry was performed. Body weight and energy intake were measured throughout the study period. The rate of weight gain was unaffected by ethanol but was increased on the HF diet. Ethanol intake averaged 14.56% +/- 1.16% of total caloric intake. Both ethanol groups compensated for added ethanol calories by reducing their intake of diet, so that total energy intake was similar in all groups. As expected, respiratory quotient decreased in both ethanol groups (LF: 0.92 to 0.88; HF: 0.88 to 0.86; P <.05). However, EE was not affected by ethanol intake. These findings demonstrate that male Sprague-Dawley rats fully compensate for the calories associated with moderate chronic ethanol consumption and maintain energy balance regardless of the fat content of the baseline diet. This compensation suggests that ethanol calories are sensed, producing an appropriate reduction in the intake of other nutrients, and/or that ethanol impacts the regulation of dietary intake mediators.