I recently did something millions of people do every year but that I'd never seriously attempted before — I embarked on a weight loss "journey". For me, that meant going from eating what I wanted, when I wanted it, to using a website to count my calorie intake and track my macronutrients. I also started stepping on the scale every day, first thing in the morning, to track my progress.
Was this a coincidence and a fluke, or an established scientific phenomenon? After it happened again the second and third month, I decide to look into it. It turns out that it's indeed quite normal to weigh more during your menstrual period. But why?
Fluid-retention as a cause of period-related weight gain
One study, noting that tons of women report feeling "bloated" and like they're retaining fluid when they hit their periods, decided to investigate this "menstrual edema" further. The authors recruited healthy women of reproductive age who were in healthy weight ranges, didn't smoke, didn't have eating disorders, didn't do shift work, and weren't on hormonal contraceptives.
The data they collected suggested that women really are more likely to retain fluid exactly on the first days of their menstrual flow. Those women who have this kind of fluid retention are about as likely to have experienced an ovulatory menstrual cycle as one during which they didn't ovulate, and hormone levels also didn't have much of an impact. Fascinatingly, however, the study discovered that more physically-active women — in their sample, runners — had a higher chance of being bloated during their periods than women who weren't as active.
The study refutes the idea, common among many women, that period-related bloating and water retention is most likely to show up in the days before menstruation. It confirms what you may well have seen for yourself on the scale, that you may be a bit heavier during your period. Water weight goes away quickly after your period ends, however, which explains why you're probably down to your pre-period weight as soon as your flow stops.
Eating more could also be responsible for period-related weight gain, mind you
Further research has separately found that women's appetite tends to reach a low point during ovulation, only to increase exponentially during the luteal phase — the time in your cycle that begins when ovulation ends and continues until you get your period. It'll come as no surprise that these appetite changes also mean women (who aren't on a strict calorie-restricting diet) will eat more during this time. This is certainly something else that can explain why the numbers on the scale might go up during your period!
Another study took this knowledge further. They came up with something they dubbed the "Menstralean diet" and tested it on overweight women of reproductive age to see if a special diet that takes the fact that weight can fluctuate due to changes associated with the menstrual cycle could promote weight loss in these test subjects.
Their recommended diet was determined according to a woman's cycle:
- During menstruation, the women were told to eat a diet consisting of more carbs and fewer proteins, some fat, and a minimal exercise routine. (The total daily calorie intake being 1600 calories.)
- In the follicular phase, between menstruation and ovulation, protein intake was increased while carbs were taken down a notch. The women were asked to engage in strength training and cardio. The total daily calorie intake was also increased by 200.
- The luteal phase, meanwhile, featured increased protein as well as fat, and again, a heavier exercise routine. The total daily calories were again 1600 at this stage.
The results? Well, the study found that following a diet tailored to the menstrual cycle in this way had the potential to increase the amount of weight loss in this group of overweight women — but also that they found the diet very hard to stick to. If you want to give this a go, however, it makes sense. If your appetite goes up during the luteal phase, upping your protein will keep you fuller for longer and is, as such, going to minimize those cravings for processed carbs you may otherwise experience!
Apparently, the effects of exercise are especially significant during the follicular phase, so that's another good thing to keep in mind if you're hoping to lose weight.
What's the message you should take away from all this?
If you experience menstrual cycles, they will impact your weight. Many women suffer from water retention around the time their periods start, something that can happen whether or not you strict to your calorie budget. You can, however, control the increased appetite and food cravings associated with the days just before your period, both by telling yourself not to give into cravings and by feeding your body more protein so the tempation to binge is that much easier to control.
Overall, however, you'll still lose weight if you burn more calories than you consume over the course of a month — even if you eat a little more when your menstrual cycle apparently calls you to do so. It may go a bit more slowly than if you were to totally ban yourself from giving into cravings, but it will happen. So, it's up to yhou whether you want to try to adjust your diet to account for your menstrual cycle, or not.