The objective of this study was to assess a circadian variation of diet-induced thermogenesis (DIT) that could favor weight gain among night workers used to eating a night time snack. Nine young men were given the same mean at 0900, 1700, or 0100. Energy expenditure was measured by indirect calorimetry 1 h before and during the 6 h after the snack. DIT was calculated as the 3 h of energy expenditure above basal metabolic rate. Morning DIT was significantly higher than afternoon DIT (P = 0.04) and night DIT (P = 0.002). Afternoon DIT was higher than night DIT (P = 0.06). We conclude that the time when a meal is consumed affects the thermogenic response and must be considered in the energy balance.