It’s about time that the medical community has begun to take a closer look at the role hormones play in women’s health, beyond fertility and reproduction. Estrogen and progesterone, for example, affect everything from cardiovascular function to cognition, yet until recently, women’s hormonal fluctuations were often excluded from research. A 2022 NIH analysis found that women remain underrepresented in clinical studies, particularly when it comes to conditions influenced by the menstrual cycle, leaving critical gaps in knowledge. At the same time, newer research is challenging some of the most common assumptions about premenstrual syndrome (aka PMS): A 2024 review in Front Psychiatry noted that neurobiological shifts, like GABA conductance and changes in neurosteroid levels, in response to fluctuating hormones, play a significant role in PMS symptoms.
In other words, there’s a lot more happening than women are led to believe. That’s the focus of The Period Brain, a new book by Sarah E. Hill, Ph.D. that argues our cultural understanding of PMS has been oversimplified — and that a deeper scientific approach can help women better recognize what’s really happening in their bodies. We have an exclusive excerpt from the book that’ll clear up a lot of confusion.
Why do women spend about one week each month feeling bloated, tired, foggy-brained, snacky, lacking willpower, and (in some cases) totally sexually dead inside? In other words, why do we have PMS? You might think hormones are responsible — progesterone increases during the luteal phase, when the body prepares for pregnancy — compared to the follicular phase, when estrogen increases. But why do we have to feel like sh*t?
The more I began to dig into these questions, the clearer it became that there are two distinct things going on.
The first is that a lot of the experiences that women report having in the luteal phase, the second half of the menstrual cycle, are normal and predictable changes that happen as a result of the body transitioning from the season of sex (or the follicular phase) to the season of pregnancy (luteal phase). They feel disordered because we haven’t been given any explanation for them. They feel like symptoms instead of experiences.
What’s the difference, you ask?
Well, when we have something wrong with our bodies, we often feel physical changes that alert us to the fact that something’s wrong. These are called symptoms. They’re smoke that emerges from the fire of pathology. Experiences, on the other hand, are noticeable changes that go on in the body that are expected as part of the body’s day-to-day function. Like when we feel hungry because our bodies need food. Or when we feel tired because we need sleep. Unlike symptoms, experiences aren’t pathological; they don’t mean something’s wrong. To the contrary, they help guide our brain and behavior in ways that enable us to survive, reproduce, and ensure that all our basic needs are met.
Many of the things that go on during the second half of our menstrual cycles are experiences masquerading as symptoms. And because we’re not taught what they are, what they mean, and what our bodies need in response to our changing hormonal states, they feel like a sign of something wrong.
Consider the metabolic changes women experience in the luteal phase. Even though all of us have been led to believe that our bodies need the same number of calories every day of the month (all else being equal), this isn’t true for women. Our metabolic needs actually increase 7-11 percent in the luteal phase relative to what they are in the follicular phase. If you are a woman who eats a 2,000-calorie/day diet, you would need to add roughly 140 calories a day to keep the body chugging along at its usual speed in the luteal phase. Now, most of us aren’t told about these changing nutritional needs — instead, we’ve all been given a set of guidelines that we’re led to believe applies to us every day of the cycle.
This is where luteal phase pathology comes in. Because when you don’t give your body enough of what it needs — in this case, energy in the form of calories — it’s not going to feel good. This is particularly true when our energy needs are high and the stakes are higher, like when the body is preparing for the possibility of pregnancy.
So, what does a body do when it’s experiencing an energy shortfall at a time in the cycle when energy is so critically important? The answer is something that most of us are all too familiar with. It’s food cravings, preoccupation with food, and — should we restrict to the point that our brain goes into overdrive when we finally give in to our body’s needs — binge-eating.
Sound familiar?
The food cravings that so many of us experience in the luteal phase are a pathological outcome of ignoring the fact that our bodies’ needs change in the season of progesterone. It’s part of what we consider PMS. And they are completely unnecessary. We suffer from food cravings, preoccupation with food, and create an unhealthy, untrue narrative about ourselves being lacking in willpower or out of control around food because we are ignoring what our bodies are telling us, because we have all been led to believe that our bodies’ needs are one-size-fits-all.
The problem is that we are not one-size-fits-all. And the reason that the luteal phase feels like such a confusing mess characterized by widespread disorder is because when you live in a world where women’s cyclicity isn’t acknowledged, any changes in what our bodies are doing take on the tint of pathology. And when we pretend these changes aren’t happening or that they don’t matter, pathology is created, because our bodies aren’t being given what they need to thrive. This is why close to 90 percent of us experience PMS. And this is why there are more than 200(!!!) “symptoms” of PMS that have been noted in the research literature. PMS is nothing more than a lazy diagnostic catch-all that is being used to give women an “explanation” for physical and psychological changes that occur in the luteal phase, whether they are occurring on purpose, or are a pathology created by ignoring our bodies’ needs at this time.
Sarah E. Hill, Ph.D., is the author of This is Your Brain on Birth Control and an award-winning researcher who has spent most of her 20+ year career studying women, relationships, and health. In addition to establishing an award-winning health and relationships lab at TCU, she has published nearly 100 academic research articles, is a sought-after public speaker, and sits on the scientific advisory boards of women’s health companies such as Flo and 28 Wellness.
