Women who experience menstrual-related weight fluctuation usually begin to gain weight around five days before starting their period and maintain an elevated weight until after the period starts. But this is highly individualized. The amount of weight gained, when this begins to happen, how long it stays elevated, and when it drops varies across individuals—and some women don’t experience menstrual-related weight gain at all!
You know your body, and you’re probably pretty familiar with how your weight is affected by your period. You might experience weight gain 7 or 8 days prior to starting your period (instead of 5), and this weight elevation might persist many days after starting your period. So, regardless of whether you’re strictly within the 5 days of starting your period or not, if you know your weight is artificially elevated as a result of your menstrual cycle, go ahead and choose that option.