Puder JJ et al. (2006) Estrogen and exercise may be related to body fat distribution and leptin in young women. Fertil Steril 86: 694–699

During the menopause, many women experience accumulation of central abdominal fat; however, this increase in abdominal fat can be prevented (in many instances) by estrogen, in the form of hormonal replacement therapy. Fat accumulation can also be reduced by exercise, but extensive exercise and a large energy deficiency can lead to amenorrhea and hypoestrogenemia. Leptin is involved in energy homeostasis, and might represent a link between energy deficiency and amenorrhea. Puder et al., therefore, investigated the relationships between serum estrogen concentrations, exercise level, body composition and leptin concentrations, in young, premenopausal women.

Overall, 50 women aged between 18 and 36 years (all with similar BMD) were studied. Participants were allocated to one of three groups: women with exercise-associated amenorrhea, normal-weight women who exercised regularly and had regular menstrual cycles, and women with regular menstrual cycles who reported less than 5 h of physical activity per week.

In women with regular menstrual cycles, estradiol concentrations were inversely correlated with central accumulation of body fat. This relationship was not observed in women with exercise-associated amenorrhea. In all women, estradiol concentrations were positively correlated with leptin concentrations, and exercise was inversely correlated with leptin concentrations, independently of body fat distribution.

The authors conclude that in young, premenopausal women, estradiol concentration and exercise level influence leptin concentrations, which in turn affect energy balance. They note that these processes occur through mechanisms that are, in part, independent of body fat distribution.