The night shiftwork on the one hand, the obesity on the other hand, are at the origin of sleep modifications. Is the overweight an aggravating factor which damages the recovering sleep? A study on sleep conducted in the laboratory on 7 reference subjects and 7 obese subjects, randomly allocated with regard to age, seniority and Body Mass Index, has shown only a small influence of the overweight on the slow wave sleep during the night shortened by shift work. Obesity does not seem to alter the REM sleep.