This study investigates the impact of circadian timing of food intake on weight gain in mice. The researchers found that mice fed a high-fat diet only during the 12-hour light phase gained significantly more weight compared to those fed during the 12-hour dark phase. Despite similar caloric intake and locomotor activity, the light-fed mice showed a tendency to be less active and consume slightly more calories, contributing to their higher body weight. The results suggest that the timing of food intake, rather than just caloric intake or energy expenditure, plays a crucial role in weight regulation. This finding has implications for developing new therapeutic strategies to combat obesity, particularly through behavioral modifications such as adjusting the timing of meals.This study investigates the impact of circadian timing of food intake on weight gain in mice. The researchers found that mice fed a high-fat diet only during the 12-hour light phase gained significantly more weight compared to those fed during the 12-hour dark phase. Despite similar caloric intake and locomotor activity, the light-fed mice showed a tendency to be less active and consume slightly more calories, contributing to their higher body weight. The results suggest that the timing of food intake, rather than just caloric intake or energy expenditure, plays a crucial role in weight regulation. This finding has implications for developing new therapeutic strategies to combat obesity, particularly through behavioral modifications such as adjusting the timing of meals.