Crazy but True: Your Cycle Helps Determine Your Calorie Burn

There are a lot of things that can affect your metabolism. Age, genetics, and diet play a role, of course, but for women looking to maximize their calorie burn, there's another factor to consider: your menstrual cycle. And we're not just talking about your period. "A woman's metabolism is affected by her hormone fluctuations throughout the month," Alisa Vitti, HHC, AADP, functional nutritionist and founder of, told POPSUGAR. Here's how to use those hormones to your advantage.

Step Up Your Workouts in the Follicular Phase

That's science speak for the phase that begins on day one of your period and ends when you ovulate. "Peak athletic ability in women occurs in the time preceding ovulation, a fact that's been studied in professional female athletes," said Dr. Felice Gersh, MD, founder of the Integrative Medical Practice of Irvine in Irvine, CA. You may even feel the difference — like you're crushing your usual Spin class.

There's a relatively simple explanation for this, Dr. Gersh said. During the luteal phase — which begins right after ovulation and ends the day before your next period — your body's production of progesterone makes it less efficient, causing it to work harder for the same results. (This actually causes you to burn more calories — more on that in a minute.) Once you're in the follicular phase, your body doesn't have to exert as much effort, so your workouts feel easier.

In other words, don't shy away from an intense sweat session during the first half of the month — because while you may not burn more calories overall, you'll never feel more on top of your game.

Think Low-Impact During the Luteal Phase

A woman's basal metabolic rate (BMR) increases significantly after ovulation, so while your workouts may feel harder, "you'll also burn more calories at rest," Vitti explained. Once you start menstruating, hormone levels drop drastically and BMR resets to a normal level.

That means this isn't the time to forgo the gym — you'll burn more calories now than at any point in the month, even if you feel crummy doing it. But increasing your workouts could lead to an entirely different problem: the more you exercise, the more you'll want to eat. "Between craving more calories and the progesterone production that's happening at this time, you can actually turn on fat storage and increase muscle wasting," Vitti said.

She suggests low-impact workouts like Pilates and yoga to help you shape muscle and keep urges to snack on empty calories at a minimum. This way, you won't cancel out that bonus burn.