In obese subjects, treated by hypocaloric diet, meal-timing was modified: a single meal in the morning or a single meal in the afternoon, given during 18 days in order to emphasize eventual modifications of circadian rhythms of serum cortisol, prolactin, TSH and body temperature. The study was performed using macroscopic approach by circadian chronograms of the mean values. The meal-timing modifications do not change the rhythm of serum cortisol and TSH; while as far as the rhythms of serum prolactin and body temperature, are concerned, in subjects given the meal only in the morning, these rhythms were suppressed.