#992 - Dr Sarah Hill - The Period Brain: How Hormones Change Women’s Behaviour - Modern Wisdom

How Your Monthly Cycle Changes Your Brain and Mood

A woman's monthly cycle has two different "jobs"—finding a partner and preparing for pregnancy—and the hormones in each phase change her brain, energy, and what she finds attractive.

A Tale of Two Halves: The first half of your cycle is all about estrogen, which makes you feel more social, energetic, and focused on attraction. The second half is run by progesterone, which shifts your body into an energy-saving, safety-first mode to prepare for a possible pregnancy.
First Half "Superpowers": When estrogen is high (around ovulation), your brain gets sharper at noticing subtle differences in potential partners, like their scent or facial features, and your sex drive is at its peak.
Second Half "Chill Mode": When progesterone takes over, your brain makes you more cautious, more sensitive to potential dangers, and more of a homebody. This is your body’s way of protecting a potential pregnancy by saving energy and avoiding risks.
Why PMS Happens: The miserable feelings often called PMS aren't a biological flaw; they're often caused by a mismatch between what your body needs (more food, more rest) and what modern life demands (acting the same every single day).
Fun Facts & Key Numbers:
- Fact: In the two weeks before their period, women’s bodies burn 8% to 11% more calories, which is why you might feel extra hungry and crave food.
- Fact: One study found that strippers who weren't on birth control earned significantly more money in tips when they were ovulating (the most fertile part of their cycle).

Quote: ">...the way that women have been handled by science and by medicine is that we're just like small, less hairy versions of men."
- What it Means: The speaker is saying that for a long time, medical research mostly studied men and just assumed women's bodies worked the same way, completely ignoring the massive impact of the menstrual cycle.
- Why it Matters: This is a huge deal because it explains why so many things about women's health, from PMS to how they react to medicine, have been misunderstood or ignored. It shows that we need to pay way more attention to female biology.
Quote: "> So like, what is the deep evolutionary wisdom behind self-loathing?"
- What it Means: The speaker is asking a big question: From an evolutionary standpoint (thinking about how humans survived and evolved), why would our bodies make us feel bad or self-critical for two weeks every month? There must be a hidden reason.
- Why it Matters: This question sets up the whole conversation. It challenges the idea that feeling bad before your period is just a random, useless problem. Instead, it suggests those feelings might be a signal from our bodies that has a deeper, protective purpose.

First, the author argues that a woman's body has two main reproductive jobs each month. The first job is to attract a high-quality partner, which is driven by the hormone estrogen. The second job is to prepare for and protect a potential pregnancy, which is driven by the hormone progesterone.
Next, they provide evidence that these hormonal shifts change everything. In the first half, estrogen makes women more energetic, social, and better at detecting signs of good genes in men (like those related to testosterone). In the second half, progesterone makes the brain more sensitive to threats, encourages rest, and increases appetite to conserve energy.
Finally, they point out that much of the suffering associated with PMS comes from society ignoring these biological shifts. We expect women to be "always on" like men, but their bodies have different needs at different times of the month. If women knew to eat more and rest more in the second half, many PMS symptoms could disappear.

Q: Why do I get so hungry and crave junk food before my period?
- A: According to the text, your body's metabolism actually speeds up in the two weeks before your period (the luteal phase). It's burning more calories to prepare the body for a potential pregnancy. So, those cravings are a real signal that your body needs more energy—up to 200 extra calories a day!
Q: Is it true that who you're attracted to can change during the month?
- A: The text says it's a "spicy topic" in science, but some research shows that when estrogen is highest (around ovulation), women are more tuned in to—and may prefer—men with features linked to testosterone (like scent or facial structure). In the second half of the cycle, this preference is less noticeable.
Q: So is being moody and tired before my period actually a good thing?
- A: From an evolutionary perspective, yes! The text explains that feeling tired makes you conserve energy, and being more emotionally sensitive makes you better at spotting potential threats to your safety or relationships. It’s your body’s ancient way of creating the safest possible environment for a potential pregnancy, even if you’re not trying to get pregnant.

Why You Should Care: Understanding this can be a game-changer. It helps explain why your energy, mood, and social battery can feel so different from one week to the next. It’s not you being "crazy" or "moody"—it's your biology at work. Knowing this can help you be kinder to yourself and plan your life a little better, like scheduling tough workouts in the first half of your cycle and planning for more chill time in the second half.
Learn More: If you found this interesting, check out the TEDx talk by the speaker in the podcast, Dr. Sarah E. Hill. Her talk is called "This is your brain on birth control," and it dives even deeper into how hormones shape who you are. You can find it easily on YouTube.