Estrogen and substrate metabolism - A review of contradictory research

The increasing number of females participating in physical activity has hei ghtened our awareness of changes in the menstrual cycle which often accompa ny physical activity. As such, there has been a considerable amount of rese arch investigating the relationships between menstrual cycle changes and bo ne mineral density, performance, ventilation and substrate metabolism. A nu mber of researchers have concluded that there may be enhanced fat metabolis m in eumenorrhoeic versus amenorrhoeic females, or in the follicular phase versus the luteal phase of the menstrual cycle, due to the theoretical estr ogen level in eumenorrhoeic versus amenorrhoeic females or the luteal phase versus the follicular phase. However, a definite relationship between rest ing estrogen level and substrate metabolism has not been clearly establishe d. In addition, the mechanisms which may be responsible for the effect of e strogen on substrate metabolism have not been addressed. It appears that th e effects of estrogen on metabolism may be via the effect of estrogen on gl ucogenic hormones or lipolytic enzymes. Therefore, the primary purpose of t his review is to explore the effects of estrogen on substrate metabolism. M enstrual cycle physiology and possible mechanisms for the effects of estrog en on metabolism, as well as previous research on estrogen and metabolism i n rats and humans, will be discussed.