Thermoneutrality at 30°C reduces by 78% the metabolic changes induced by calorie restriction in the hypothalamus and by 39% in plasma, compared to standard laboratory housing at 22°C, indicating that the metabolic response to calorie restriction is attenuated under thermoneutral conditions and that housing at 22°C amplifies this response beyond physiological levels.

When food intake drops, the brain detects the energy shortage and decides whether to save energy by lowering body temperature. If the environment is cool, the brain uses arginine to make nitric oxide, which opens blood vessels and causes heat loss, dropping body temperature. This forces the body to burn fat and break down muscle to make more energy. If the environment is warm, the brain does not make nitric oxide, so body temperature stays normal, and the body does not need to burn fat or break down muscle. The same raw material, arginine, gets used for different purposes depending on temperature: heat loss in the cold, cell repair in the warmth.