Daniel MT Fessler, an anthropologist at UCLA, argues that hormones decrease interest in food in human women and a large variety of other animal species during the period of ovulation.

During this ovulatory period, a California anthropologist now finds, women naturally and unwittingly eat some 5 to 25 percent less than at other times.

The purpose of the decrease in appetite is to cause femals to spend less time searching for and consuming food in order to free up more time for mating.

Women's bodies must be telling them to give less attention to food and more attention to sex during the time each month when they could become pregnant.

Fessler speculates that the mechanism of action is that higher blood estrogen potentiates the effect of the hormone cholecystokinin. Cholecystokinin is believed to play a role in inducing satiety and is released by the small intestine after meals.

You can read the abstract of the paper from The Quarterly Review of Biology.

Fessler is an advocate of evolutionary psychology as an approach for understanding human nature and behavior.

Evolutionary psychology grew out of sociobiology and, like its predecessor, is based on the assumption that human behavior has been importantly shaped by natural and sexual selection. However, evolutionary psychology differs from sociobiology in a number of fundamental ways. While sociobiology is content to treat the mind as a black box, evolutionary psychology asserts that because behavior is a product of mind, in order to shape behavior selective forces must have shaped the mind. Moreover, because selective forces are highly specific, the mind ought to consist of multiple independent systems, each a response to a particular selective force. Lastly, because foraging in small groups probably constituted the principal adaptation throughout most of hominid evolution, selection will have operated to maximize fitness within this social and physical context.

Human minds are thus seen as a package of proclivities and capacities, each of which served a specific function in our foraging past.

Fessler has additional information about his areas of research on his UCLA web site.