Lack of association between changes in plasma leptin concentration and in food intake during the menstrual cycle

Background Changes in plasma leptin concentration and food intake occur dur ing the menstrual cycle; because leptin regulates food intake, one could hy pothesize that changes in plasma leptin concentration and in food intake ar e associated throughout the menstrual cycle. However, no data have ever bee n provided to support such a relationship. The aim of our study was to inve stigate, during the different phases of the menstrual cycle, (a) the change s in plasma leptin concentration and, if such changes were demonstrated, (b ) the potential relationship between the changes in plasma leptin concentra tion and food intake. Design The study was designed as an observational study. The plasma leptin concentration was determined in 16 healthy, young women during different ph ases of the menstrual cycle. At the same time, the basal metabolic rate (BM R), respiratory quotient (RQ) and food intake (FI) were also determined. Results The plasma leptin concentration increased throughout the menstrual cycle (P < 0.01 for trend) and was significantly correlated with plasma pro gesterone concentration (r = 0.55, P < 0.007, for follicular phase, r = 0.5 8, P < 0.02, for the periovulatory period and r = 0.57, P < 0.02, for the l uteal phase). No significant differences in BMR and fasting RQ throughout t he different phases of the menstrual cycle were found. In contrast, FI sign ificantly declined in the periovulatory phase. No significant correlations between BMR, RQ and FI values and fasting plasma leptin concentration at al l menstrual phases were found. Conclusion Changes in plasma leptin concentration and in food intake were f ound at different phases of the menstrual cycle. Nevertheless, no correlati on among those parameters at any phase of the menstrual cycle was observed.