Diet-induced thermogenesis in cafeteria-fed rats: a myth?

Oxygen consumption (VO2), carbon dioxide production (VCO2), and respiratory quotient were measured in rats given a high-fat cafeteria diet of the type that is said to promote diet-induced thermogenesis. No significant difference in the measurements as compared with controls was found at room temperature, at 5 degrees C, or in animals exposed to cold for several weeks. The result was the same whether open- or closed-circuit methods were used. The stimulatory effect of norepinephrine on the VO2 was identical in each dietary group. These results cast doubt on the alleged identity of diet-induced and nonshivering thermogenesis and may reflect the change in body composition of the animals rather than a primary response to dietary variation.