Sex hormones effects on the metabolic, endocrine, and eating physiological responses to a mixed meal in women

Sex differences in the response to a meal have been reported, but the effect of endocrine, metabolic or eating physiology factors remains unclear. Different study protocols involving either fixed meals or ad libitum caloric intakes among genders may have confounded this issue. Recently we implemented a study protocol of meal administration with the purpose to evaluate these factors controlling for food intake normalized to individual daily caloric intake (TDI). We found that when mixed meals are normalized to TDI, genders show similar metabolic, insulin and ghrelin responses but an earlier hunger reduction and satiety stimulation in women. We did not evaluate, however, within females, the effect of sex hormones on the above mentioned variables. We evaluated 16 females (age 24.8±2.9yr, BMI 21.3±1.9 kg/m2) not assuming oral contraceptives. We compared among menstrual cycle phases and across levels of sex hormones the metabolic, hormonal and satiety responses to a mixed meal, carefully normalized to TDI. Subjects consumed a meal providing 40% of TDI in energy (60% carbohydrates, 25% lipids, 15% proteins). Blood was sampled at 0, 10, 20, 30, 45, 60, 90, 120 and 180 min for glycemia, insulin, c-peptide and ghrelin, and Visual Analogue Scale assessment of hunger and satiety was performed every 30 min. At baseline, FSH, LH, estradiol and progesterone were measured. Our preliminary data show that in females sex hormone levels do not affect the metabolic and insulin responses to the meal. In contrast, an inverse association between estradiol and satiety sensation were observed at each considered time, whereas FSH was significantly inversely associated to basal and T60 ghrelin concentration. This data are not congruent with expectations based on the knowledge that in women food intake is lower during the ovulatory and greater during the luteal phases of the cycle and that estrogens may exert a suppressive effect. Therefore further detailed studies are warranted.