Abstract:

This chapter aims to review the mechanisms underlying the fluctuations on appetite and food intake that occur during the reproductive cycle in both animals and humans. Research has shown that food intake is reduced during the periovulatory period and that this effect is abolished by ovariectomy. Estradiol has been deemed as the main hormone responsible for this change. It exerts its effects through activation of nuclear estrogen receptors in brain areas such as the hypothalamus, hindbrain and reward system. In addition estradiol also seems to increase the satiating potency of peripheral anorexigenic signals which leads to an early termination of meals. During the luteal phase there is an increase on intake that has also been well documented. Although the underlying mechanisms are still not totally clarified, they point toward a progesterone mediated antagonism of estradiol’s effects. Food choice is also reviewed and the current literature offers contradictory results with some reports finding that there is no preference for macronutrients whereas others found an increase in fat, carbohydrate or protein intake. Studies performed in our laboratory have found that similarly to others, intake is increased in the luteal phase, but interestingly this is not accompanied by a variation of subjective measures of appetite supporting the theory of a weakened post-meal satiety in this phase. The chapter finalizes with a review of neuroimaging studies which are a relatively recent addition to research and therefore still quite limited in terms of findings. To date the main variations in brain activity in response to food images seem to occur in areas related to visual processing. This has led to the preliminary conclusion that an additional mechanism by which reproductive hormones alter food intake is by change its salience across the menstrual cycle.