“Our goal was to investigate how a woman’s menstrual cycle impacts consumption desires, product usage, and dollars spent within the food and beautification domains” says Gad Saad, professor of marketing at the John Molson School of Business and holder of the Concordia University Research Chair in Evolutionary Behavioral Sciences and Darwinian Consumption. He is also first author of the paper, “Calories, beauty, and ovulation: The effects of the menstrual cycle on food and appearance-related consumption,” published in Journal of Consumer Psychology.

Working with his doctoral student and co-author Eric Stenstrom, Saad recruited hundreds of participants by canvassing classes at Concordia university. Through a careful selection process, 59 female participants were chosen. Over a period of 35 days, the women kept detailed diaries that chronicled beautification behaviours, clothing choices, calorie consumption, and purchases.

Through analysis of daily responses to survey items such as to what degree the respondent wore clothes that attracted sexual attention, spent time making herself beautiful, sun bathed, and ate highly caloric foods, a distinct pattern emerged. There was a marked increase in women’s appearance-related behaviours during the fertile phase of the menstrual cycle (roughly days eight to 15 of a 28-day cycle). Women were also more likely to spend more money on clothes during the fertile phase.

There are Darwinian reasons at work here, explains Saad, who investigates the biological and evolutionary roots of consumer behavior in his books, The Evolutionary Bases of Consumption and The Consuming Instinct.

“In ancestral times,” he explains, “women had to focus more time on mating-related activities during the fertile phase of the menstrual cycle, when the likelihood of conception was highest. Those same psychological and physiological mechanisms now lead women to engage in greater consumption of products relevant to reproductive drives during the fertile phase of their cycle.”

When it came to food, however, there was a distinct dip in consumption: it’s the luteal (infertile) phase that sees the peak in cravings for and consumption of highly caloric foods (days 16-28). There was also a pronounced spike in food purchases during the luteal phase.

Evolutionary forces are at work here too, says Saad. “Women consume more calories during the luteal phase because they’ve evolved psychological and physiological mechanisms that favoured non-mating-related activities like food foraging during the non-fertile phase of their cycles. Different Darwin pulls, such as mating versus food, take precedence depending on a woman’s menstrual status.”

Although the idea that one’s calorie cravings, clothing choices and shopping purchases are shaped by the ovulatory cycle might make some women feel oppressed by evolution, Saad says there’s still reason to take heart.

“These consumption behaviours take place without women’s conscious awareness of how hormonal fluctuations affect their choices as consumers. Our research helps highlight when women are most vulnerable to succumbing to cyclical temptations for high-calorie foods and appearance-enhancing products. These findings can help women to make choices for themselves contrary to the old canard of biological determinism.”

Saad thinks that one possible result could be the development of a consumption related app to help women track their particular daily shopping vulnerabilities. If a woman’ssmart-phone warns “today’s day 24 of your cycle – avoid grocery shopping!” a woman can be empowered by the conscious awareness of how biology might be adversely affecting her behaviour – and her wallet.

Republished with permission from Concordia University.