Way back in the 1920s researchers figured out something that women have known first-hand for a long time—we eat more or less during different phases of our menstrual cycle.
It might sound something like this sometimes: "My hormones made me go crazy, and I ate whole carton of rocky road ice cream in one sitting."
There's more to it, though. It turns out that we eat less when our estrogen is high. The combination of a drop in estrogen and an increase in progesterone is why women eat more, and experience cravings during certain phases of their cycle..
Not only is a change in appetite linked to estrogen levels, but cravings for chocolate, sweets, salty foods, and food in general all increase when estrogen is low. I’m sure some of you are thinking, “Duh. Welcome to my life. This isn’t exactly news.”
Here’s the thing: while many women have personal experience with it, you rarely hear about the underlying physiology. Instead, you get comments like:
“It’s just hormones.”
“Women get cravings. It is what it is.”
“You need to be more disciplined.”
All of these explanations and comments come across a patronizing. Worse, by not discussing the specifics it may feel psychosomatic—it’s all in your head. The specifics, like which parts of your brain—and which appetite hormones—are affected by your sex hormones, can help you come up with some strategies for dealing with the monthly physiological fluctuations you will experience with your appetite.
For most women the menstrual cycle takes about 28 days and goes through two phases, follicular and luteal. Follicular phase is from Day 1 of menstruation (bleeding) to ovulation (release of the egg) about 14-15 days later. Luteal phase is from ovulation thru to the next menstruation (Days 14 to 28). These phases are regulated by two hormones, estrogen and progesterone, as their levels rise and fall throughout the cycle.
Great! Now we’re all caught up with 7th Grade sex ed!
What nobody mentioned was that the menstrual cycle changes how quickly you feel full and how rewarding you find food. Estrogen is the big player in how much you eat at each sitting and how much you end up eating in a whole day. The more estrogen, the less you eat.
Yes, estrogens, plural. There’s more than one. There are actually three: estrone, estradiol, and estriol. Of the three, you’ve probably heard of the big one, estradiol. It is the most understood and the one most involved in hunger and fullness.
Estradiol goes up during the follicular phase, peaking right before ovulation, and then goes down during the luteal phase. In the follicular phase when estradiol is higher, you’ll experience less of an appetite. When estradiol goes down, in the luteal phase, your appetite increases.
Estradiol greatly influences the amount of calories you end up eating. Some studies found that women ate on average 240 more calories per day during the luteal phase (lower estradiol), compared to their intake during the follicular phase. Some studies show it may even be as high as 600 more calories per day!
There’s usually no difference in how often you eat, but estradiol affects your meal size. When more estradiol is present, you will feel full and satisfied sooner, so you are likely to eat smaller meals during this time. When less estradiol is present, it could take a little longer for you to reach a point of satiety at each meal, which means you’re more likely to eat larger meals during this time.
Food cravings can happen at any time throughout the cycle, but with lower estradiol those cravings are stronger and happen more frequently.
What type of food do you crave? Fat? Carbs? Protein? It seems that cravings don’t show up in the same way for everyone. Some studies found women ate proportionally more protein at lower estradiol levels. Others found women ate more fat. Still others found that women ate more carbohydrates. So, it’s hard to say. Scientists have no idea, and the answer is likely a lot more complicated. It could depend on preferences or perhaps on environmental demands.
There are parts of the brain that have sensors for estradiol (estrogen receptors). The presence of estradiol can decrease your food intake and makes you feel more content after a meal (increased dopamine binding). When estradiol decreases, those parts of your brain start telling you that you’re not quite full, and you don’t feel quite as content after a meal.
Lower estradiol has a direct effect on your brain. You’re not lacking discipline or being “bad” or “crazy.” What you’re experiencing is a very real response to neurological signals.
How potent is estradiol? Injecting estradiol right into certain parts of your brain regularly can decrease how much you eat, which over time, will result in lower body weight and lower weight set point. Pretty cool, but I wouldn’t recommend it.
While you have estradiol acting right on your brain, telling you to stop eating and making you feel a greater reward for eating, it also works indirectly on the brain. Estradiol modifies how hunger and fullness hormones work. Two of the more well-known and understood hormones, ghrelin and CCK, change depending on how much estradiol is around.
There’s a hormone that makes you feel hunger when your stomach is empty. It’s called ghrelin. The more ghrelin there is, the hungrier you feel. If it’s been a while since you ate, your stomach makes ghrelin and tells your brain, “Hey, how about some food?” As you eat, you make less ghrelin, and eventually your brain stops getting the, “I’m hungry” message.
Estradiol decreases ghrelin’s “I’m hungry” message in two ways: partly at your brain and partly by suppressing how much ghrelin your body makes. More estradiol = less ghrelin = less hungry = less food consumed.
Another hormone that regulates your appetite is CCK, which makes you feel full after you eat. Estradiol helps you feel fuller faster by increasing the potency of CCK. Again, you’re not crazy during that time each month when you feel like you’re just never full and satisfied.
By the way, these are two reasons to focus on eating slowly. It takes a while for ghrelin to decrease and for CCK to get to your brain.
Most women know their cycle changes how they eat, but many experience a disconnect about why. These hormonal changes have a real impact on your body’s way of detecting when you’re full or what you want to eat. Yet, most women see it as this crazy thing that happens to them. They feel that somehow this is their fault for not being disciplined enough, and they end up feeling guilty and beating themselves up for wanting to eat more.
That’s the problem.
We need to acknowledge this information and talk about it. It’s normal biology, and you can take steps that to help you navigate those higher-appetite days.
It helps to know that as estradiol goes down, you will feel hungrier, not quite full, and always craving one thing or another. Similar to telling someone who is hopped up on adrenalin to “just relax” after a near car crash, telling a woman to “just be more disciplined” isn’t helpful. It isn't about discipline. There are practical things you can do to manage the effects of these hormonal changes:
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