A colleague came into my office the other day to show me a fab jacket she had just bought. That got us started talking about a favorite activity—shopping. During this entertaining conversation, she pondered why she sometimes succumbs to the temptation to buy a pair of outrageously expensive and sexy sling-backs with scarcely a second thought, while at other times it is easy to pass up the shoe store but impossible to resist the allure of a gourmet market. “I guess it just depends on my mood,” she mused.

“More likely, it’s because of your menstrual cycle,” I told her, and then shared the fascinating findings of a new study that had just come across my desk.

The scoop: 59 women of childbearing age were asked to keep diaries for 35 days, recording the details of their daily lives—including the purchases they made, the types of foods they ate, the kinds of clothes they wore and the beauty routines they followed.

Researchers then analyzed each diary based on where the woman was in her monthly cycle. For instance, based on a typical 28-day cycle, the menstrual phase is on days one to four, when bleeding occurs…the follicular phase is on days five to 14, with ovulation and the woman’s fertile time occurring during the latter portion of the phase…and the luteal phase is on days 15 to 28, when the opportunity for conception has pretty much passed for that month. Analyzing the diaries, the researchers discovered clear patterns…

  • During their most fertile time of the month, the late follicular phase (the second week of their cycles), the women spent more money on clothes…spent more time polishing their appearance…wore sexier, more attention-grabbing attire…and ate less overall.
  • During the nonfertile luteal phase, the women spent more money on food…felt hungrier and ate more overall…and were particularly likely to crave high-calorie fare.
  • Dollars spent on products not related to beautification or food did not change significantly over the course of the menstrual cycle.

Explanation: Our evolutionary roots. In ancestral times, the fundamental human drive to reproduce encouraged women to pay more attention to their looks during their fertile times in order to attract potential mates…while during nonfertile times, women focused on non-mating-related activities essential to survival, such as food foraging. And today, women continue to be influenced by those same innate drives.

Now that you’re consciously aware of what you’re likely to buy when and why, you may want to use this understanding to help keep your spending and your eating under control. The trick: Avoid clothing boutiques and jewelry counters when you’re in the middle of your cycle…and stay out of gourmet shops and grocery stores (or at least bypass the snack aisles) during the last half of your cycle.

Will you need to do this forever? No, just until menopause. At that point, researchers speculate, women’s shopping patterns would no longer be influenced by the time of the month.

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