Q. When it’s “that time of the month” I feel like my stomach is a bottomless pit. I can eat and eat. I also crave sweets. Is this normal?

• A. In a word: Yes. It’s very common to experience an increase in appetite or cravings for certain foods just before or during your period.

The idea that getting one’s period causes an uncontrollable desire for sweets is so heavily reinforced in our society that it could easily become a self-fulfulling prophecy.

But how much of this is biological or physiological and how much of it is in our heads? After all, the idea that getting one’s period causes an uncontrollable desire for chocolate or other sweets is so heavily reinforced in our society that it could easily become a self-fulfulling prophecy. If we believe that we are the victim of forces beyond our control, it gives us an excuse to abandon our usual self-restraint or to justify our excesses.

But while it may be subject to some exaggeration, the phenomenon of hunger and cravings associated with a woman’s period is not entirely imagined.

How the menstrual cycle affects appetite and metabolism

Levels of the hormone progesterone rise in the second half of the menstrual cycle, leading up to the onset of menstruation. This hormone triggers changes in the uterus that allow it to support a pregnancy. It’s also known to have an appetite-stimulating effect.

Non-human animals—who are presumably immune to cultural messaging—tend to eat more and favor more calorie-dense foods in the week or two leading up to the onset of the menstrual cycle. Perhaps this is the body’s way of preparing for the extra energy demands of being pregnant.

We are not completely at the mercy of our hunger hormones.

However, there are a couple of other compensating factors to consider. Levels of the hormone leptin also rise during the second half of the cycle, and this appetite-regulating hormone tends to suppress the urge to eat. So, we are not completely at the mercy of our hunger hormones.

You also burn more calories in the days leading up to your period. It’s an oft-repeated myth that women burn up to 500 extra calories per day during their period. In reality, you probably burn an extra 500 calories per cycle. But if you’re a bit hungrier than usual, that may be part of the reason. As along as you don’t go overboard, that extra calorie burn could cancel out an extra snack or two.

You may gain and lose a few pounds every month, but most of the change is due to temporary water retention.

In effect, the typical changes in appetite hormones and metabolism during your menstrual cycle largely balance themselves out. You may gain and lose a few pounds every month. While that may be annoying, it’s not necessarily cause for alarm. You’re not gaining and losing several pounds of fat each time. Most of the change on the scale is due to temporary water retention.

The serotonin effect

Cyclical changes in neurotransmitters may also play a role in your appetite. Serotonin, for example, has a number of functions throughout the body. It’s perhaps best known for its effect on mood, creating a feeling of well-being. But it’s also involved in cell-to-cell communications, sleep, digestion, and more.

When you crave carbs, you’re literally self-medicating.

When serotonin levels fall, it can create cravings for carbohydrate foods—a big dose of carbohydrates will cause a temporary rise in serotonin levels. When you crave carbs, you’re literally self-medicating.

For many women, serotonin levels remain relatively level throughout their cycles. But for some women, serotonin levels fall prior to the onset of menstruation and this could also explain cravings for chocolate or carbohydrates in the days leading up to your period. This seems to be particularly true for women to who suffer from PMS or who are prone to depression or seasonal affective disorder (SAD).

Many people find that the more refined carbohydrates they eat, the more they want.

The problem with using carbs to self-medicate for a serotonin deficiency is that eating a lot of refined carbohydrates can cause other unwelcome consequences. For one thing, many people find that the more refined carbohydrates they eat, the more they want. (Especially if it’s also serving as an anti-depressant!) So, instead of a periodic cycle in which your appetite and metabolism rises a bit and then falls, your intake simply escalates.

Fortunately, carbs are not the only way to boost your serotonin levels. In our conversation on Food and Mood, psychologist Dr. Ellen Hendricksen offered the following tips:

If you need a quick way to enhance your mood, a few minutes of aerobic exercise like a quick walk or even some jumping jacks in your office, exposure to sunshine, doing a nice favor for someone, or even simply smiling, are all proven ways to boost your mood.

Strategies for coping

Now that we have a better understanding of what’s happening in our bodies and our brains before our period, let’s talk about how to cope.

1. When faced with menstrual munchies, try to stick to yummy but healthy foods that fill you up: fruits, vegetables, whole grains, and protein-rich foods.
2. If the cravings feel emotional, see if you can find other non-caloric ways to lift your mood. Take a walk in a beautiful place, get some exercise, schedule a massage, take a yoga class, watch a funny movie, or call a favorite friend.
3. Make sure to get plenty of sleep. Being under-rested can powerfully increase appetite and cravings.
4. Consider giving in to that chocolate craving. After all, chocolate contains compounds that lift your mood. But instead of breaking out the king-sized bag of M&Ms, treat yourself to an ounce or two of the best quality chocolate you can find.

If you’re struggling with severe PMS symptoms or depression, please don’t struggle alone. Seek the support of a health care professional. There are treatments that can dramatically improve your quality of life.