Researchers from Concordia University found that women's menstrual cycles affected their shopping, eating and grooming patterns.

According to the study's lead author Gad Saad, a professor of marketing at the university's School of Business, they sought to understand if women's menstrual cycles affected their desire to buy things, what they bought, and how much money they spent. They asked 59 women to take journals of their daily consumption habits, as well as their beauty routines, over the course of 35 days. They also analyzed surveys the women took, which asked questions about clothing choices, how long they spent grooming themselves, eating high-calorie foods and whether or not they sunbathed.

During the most fertile days of a woman's menstrual cycle (approximately from day eight to day 15 of a 28-day cycle), women were more attentive toward grooming and personal upkeep. The women were more likely to buy clothes and were less likely to eat high-calorie foods than on their relatively infertile days. Their appetites increased when they were no longer fertile, or day 16 of a 28-day cycle, which just about coincides with the beginnings of premenstrual syndrome (PMS).

Researchers think that the basis for this trend lies in evolution. In ancestral times, they theorize, women needed to pay more attention to their looks in order to lure in men when they were most fertile. Priorities shifted from food to appearance when women were most fertile, and shifted back to food when that was no longer the case.

Recently, there has been a lot of research on ovulation and its effects on behavior. Commonly cited research says that women are considered more attractive while they are ovulating. Other researchers have stated that ovulation changes women's behavior and the types of men to which they become attracted, becoming increasingly interested in men who are handsome and charming but uninterested in settling down.

But maybe men do not actually think that women are more attractive during ovulation. Maybe the women are wearing newer, more flattering clothes.

The research was published in the Journal of Consumer Psychology.