We studied interindividual variation in body temperature and energy expenditure, the relation between these two, and the effect of mild decrease in environmental temperature (16 °C versus 22 °C) on both body temperature and energy expenditure. 9 Males stayed three times for 60 hours (20.00-8.00 h) in a respiration chamber, once at 22 °C, and twice at 16 °C, in random order. 24h EE, diet induced thermogenesis (DIT), sleeping metabolic rate (SMR), activity induced energy expenditure (AEE), and rectal and skin temperatures were measured. Rank correlation test using data of six test days showed significant inter-individual variation in both rectal and skin temperatures, and energy expenditures corrected for body composition. Energy expenditure (24hEE and SMR adjusted for body composition) was significantly related to rectal temperature. Short-term exposure to 16 °C of the subjects caused a significant decrease in body temperature (both skin and core), an increase in temperature gradients, and an increase in energy expenditure. The change in body temperature gradients was negatively related to changes in energy expenditure. This shows that inter-individual differences exist with respect to the relative contribution of metabolic and insulative adaptations to cold.