Food cravings out of control? Knowing why cravings happen will help you fight them – and help you maintain a balanced healthy diet and weight.

When your food cravings hit

You've probably noticed that you feel your strongest food yens at specific times of the day—or month.

1) Mid-afternoon food cravings (from about 3-6 p.m.)

By far the greatest number of cravings occur late in the day, when our blood glucose drops, making us sluggish and in need of a lift. All it takes now is a cue—a fast-food billboard on your way home or a co-worker's candy bar—to bring on major sugar cravings or carb cravings.

2) When we're upset or bored or need stress relief

Bad moods frequently give rise to cravings. We imagine that if we eat a cookie or a chocolate bar, we'll feel better—and often we do. Carbohydrates—sweet or starchy foods—increase the secretion of the brain chemical serotonin, which in turn can improve mood and provide temporary stress relief.

3) Carb cravings and chocolate cravings before your period

Research shows that many of our cravings for chocolate and carbohydrate-rich foods are particularly intense in the days leading up to menstruation. Experts theorize that women may engage in emotional overeating of carbs in an attempt to raise serotonin levels to counter the bad moods and mild depression related to PMS.

Also, we actually need more calories premenstrually, so it would make sense we might experience more cravings if we're short on energy. Although there have been a number of studies examining cravings and the menstrual cycle, scientists still don't know exactly why some women seem to engage in emotional overeating or crave carbs, chocolate and other sugary foods before their periods.

Discover more about cravings, including sugar cravings and carb cravings, from Shape.