Way back in the 1920s, researchers confirmed something that women have known first-hand for a long time: We eat different amounts during different phases of our menstrual cycle.
Maybe you've heard a friend or client (or yourself!) say something like, "I ate a whole carton of rocky road ice cream in one sitting... my hormones made me do it!"
But while many women have personal experience with it, you rarely hear about the underlying physiology. Instead, you get comments like:
"Explanations" and comments like these come across as patronizing. Worse, by not discussing the specifics, it can lead women to feel like it's all in their heads. But there is a physiological explanation behind this.
We eat less when our estrogen is high.
When estrogen drops and progesterone increases, we eat more and experience more cravings for chocolate, sweets, and salty foods (and food in general).
Knowing 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 appetite fluctuations you'll likely experience. Let's look at all of this in more detail.
For most women, the menstrual cycle takes about 28 days and goes through two phases: follicular and luteal. The follicular phase lasts from day 1 of menstruation (bleeding) to ovulation (release of the egg) about 14–15 days later. The luteal phase lasts from ovulation until the next menstruation (so typically from about day 14 to day 28). These phases are regulated by two hormones, estrogen and progesterone, as their levels rise and fall throughout the cycle.
While you might have learned about some of this in 7th grade sex ed, your teacher probably didn't mention that the menstrual cycle changes how quickly you feel full and how rewarding you find food!
To more fully understand the effect of hormones on our appetite, we need to talk about the role of estrogens. Yes, estrogens, plural. There are actually three types of estrogen: estrone, estradiol, and estriol. Of the three, you’ve probably heard of the big one, estradiol. It's the most understood and the one most involved in hunger and fullness, including how much you eat at each sitting and how much you end up eating in a day.
Estradiol goes up during the follicular phase, peaking right before ovulation, and then goes down during the luteal phase. As I mentioned earlier, the more estrogen (in this case, estradiol), the less you eat and the lower your appetite. 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're likely to eat smaller meals during this time.
When estradiol goes down, in the luteal phase, your appetite increases and it can take longer to reach a point of satiety at each meal, which means you’re more likely to eat larger meals during. Some studies found that women ate on average 240 more calories per day during the luteal phase, compared to their intake during the follicular phase. Some studies show it may even be as high as 600 more calories per day!
Additionally, while food cravings can happen at any time throughout the cycle, those cravings are stronger and happen more frequently with lower estradiol.
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 make 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” when you have stronger cravings and eat more food. 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. Over time, it results in lower body weight and lower weight set point. Interesting... but I wouldn’t recommend it.
While you have estradiol acting directly on your brain, influencing your hunger cues 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.
Ghrelin makes you feel hungry when your stomach is empty. 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. Eventually, your brain stops getting the “I’m hungry!” message.
Estradiol decreases ghrelin’s hunger cue partly in 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 and satiated after you eat. Estradiol helps you feel fuller faster by increasing the potency of CCK. Again, if you feel like you’re never full or satisfied at certain times of the month, there's a tangible physiological reason behind it.
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 and what you want to eat. Yet, many women tie it to a lack of willpower, like it's their fault for not being disciplined enough. 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, but there are steps you can take to help navigate those higher-appetite days.
It helps to know that as estradiol goes down, you will feel hungrier and not quite as full, and you may have cravings. Similar to telling someone who is hopped up on adrenaline to “just relax” after a stressful incident, telling a woman to “just be more disciplined” isn’t helpful. It isn't about discipline.
Here are five practical things you can do to manage the effects of these hormonal changes:
#1. Eat slowly. Really slowly. Set a timer and take 20 minutes or more. This will feel painfully slow, but it takes a while for ghrelin to decrease and for CCK to get to your brain. Slowing down will help you manage how much you eat at a meal so you can eat enough for your needs. (This is a good habit to practice regularly, not just during that time of the month!)
#2. Keep track of what you want to eat during your luteal phase and be prepared. If you want chocolate, eat chocolate. Find the best version, have it available, and eat it very slowly. Trying to white-knuckle a craving rarely ends well. Planning is usually more helpful than abstaining completely.
#3. Try to get seven to nine hours of sleep. Sleep deprivation can mess with our hormones and tends to make us eat more, so try to keep things a little easier on yourself.
#4. Be prepared, like a Girl Scout. Make sure you plan for what you know is coming. Things like planning meals, eating from smaller plates, eating with smaller utensils, and if possible, avoiding all-you-can-eat buffets on days when you have low estradiol.
#5. If you want to know exactly what’s going on with your cycle, track your morning body temperature. A drop in estradiol is related to an increase in body temperature. Regularly take your temperature when you wake up, before you do anything else, and write it down. A jump in temperature means estrogen is falling (start of the luteal phase).
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