Reduction of food intake in the ovulatory phase of the menstrual cycle.

Food intake was weighed and recorded daily during one complete menstrual cycle in 18 healthy normally menstruating women. Urinary luteinizing hormone indicated the time of ovulation. Mean daily intakes of energy, macronutrients, and alcohol were calculated for five phases during the menstrual cycle: menses, postmenses, ovulatory, postovulatory, and premenses. Weekly variations were also measured. Energy intake was lowest during the ovulatory phase compared with postovulatory, premenses, and menses phases (p less than 0.05). The maximum difference, 1.36 MJ (324 kcal)/d, occurred between ovulatory and postovulatory phases and was twofold higher than the increase of 0.64 MJ (152 kcal)/d observed at weekends. This reduction of food intake at ovulation has not been previously described in humans. It coincides with the expected peak in circulating estrogen levels and is consistent with the hypothesis in animal models that estrogen is an appetite suppressant.