Why You Crave Sugar Before Your Period

The week before a period is when otherwise consistent eating most often comes apart. There are reasons, and they're not about resolve.

What changes across the cycle

Insulin sensitivity shifts. It's generally somewhat lower in the luteal phase — the second half, after ovulation — meaning the same food can produce a slightly larger glucose response than it would two weeks earlier.

Energy needs rise modestly in the luteal phase. Appetite increases accordingly, which is physiology rather than weakness.

Progesterone rises, and it has sedating effects and influences appetite.

Serotonin falls in the late luteal phase, which is thought to underlie the specific pull toward carbohydrate — eating carbohydrate raises tryptophan availability and thus serotonin. The craving has a mechanism.

I'd note the evidence here is a mixture of solid physiology and reasonable inference. The direction is well supported; the magnitude varies enormously between individuals.

What tends to help

Eat more, deliberately, in the luteal phase. This is the counterintuitive one and it's the most useful. Trying to hold intake flat across the cycle means fighting a genuine increase in requirement, and losing that fight in the form of an evening that goes badly.

Protein at every meal, and more of it. Satiety matters most in the week it's hardest.

Don't restrict. Restriction in the luteal phase reliably produces the bingeing that follows. This is the single most common pattern and it's entirely avoidable.

Pair the carbohydrate you want. If you want something sweet, have it after a meal with protein in it rather than alone at nine.

Magnesium has some evidence for premenstrual symptoms, though it's not overwhelming.

Track the cycle alongside your eating. Recognizing that the difficult week is the same week each month removes a great deal of the self-blame, and that alone changes behavior.

The reframe

If your eating is consistent for three weeks and difficult for one, that's not an inconsistent person. That's a monthly physiological cycle doing what it does, and a plan that accounts for it works better than one that doesn't.

Try this week: if you're in the luteal phase, add an extra protein-containing snack rather than trying to hold the line.

Education, not medical advice. Severe premenstrual symptoms, including PMDD, warrant medical assessment.