Periods 101: Your Cycle, Your Hormones, and the Truth Behind “Balancing” Them
Because what we learned at school barely scratched the cervix… I mean surface — and didn’t exactly equip us for the 450+ periods we’ll have in our lifetime.
Welcome back to Science & The City, where we cut through the wellness noise and get real about women’s health.
Today, we’re going back to basics — because, let’s face it, GCSE Biology taught us sweet FA when it comes to truly understanding what’s actually going on in our bodies each month. It definitely didn’t prepare us for the fact that, on average, a woman will spend around 7.5 years of her life menstruating (thanks ChatGPT for crunching those numbers). Yep — that’s over 2,500 days spent bleeding, cramping, craving, and (often) pretending like it’s all totally fine.

So let’s break through the shame, ditch the silence, and talk about our menstrual cycle, our sex hormones, and why understanding them matters for far more than just fertility. Because, spoiler: your period isn’t just a “monthly inconvenience” — it’s one of the most powerful indicators of your overall health as a woman.
Side note: I cannot claim the cervix joke — that was the genius Alice Brine when on set filming The Cycle Society.
The Female Menstrual Cycle: Why do I feel like four different people each month?
This beautiful piece of physiology above shows how your hormones fluctuate every single month – something which plays out in roughly 50% of the population. And yet, it remains one of the most under-researched areas of human physiology — with more scientific studies published on erectile dysfunction than on the female menstrual cycle. It is the reason why us women are so often excluded from scientific studies altogether, and instead, we become reduced to a footnote: “Results may vary for menstruating women.”
While the diagram above shows the textbook version — a neat 28-day cycle — that’s actually pretty rare. Most women experience cycles that range anywhere from 21 to 40 days. And the length of your bleed? It’s not always the “standard” 5–6 days we’re told about in school. The truth is, there’s a wide spectrum of what’s normal — and understanding your normal is what matters most. When things shift away from that, it’s time to start asking questions (more on that later).
But first — let’s talk about why “we’re all so hormonal.” And thank goodness we are, because these monthly hormonal fluctuations don’t just affect fertility. They influence your mood, metabolism, sleep, energy levels, and even your gut health (ICYMI: I covered that in last week’s post).
So, let’s break it down: what’s actually going on during each phase of your cycle, and how are your two powerhouse hormones — oestrogen and progesterone — calling the shots?
While we’re built on a ~28 day (ish) hormonal rhythm, men operate on a 24-hour clock (how convenient for them). Testosterone rises and peaks in the morning, setting them up for the day, then gradually declines — priming them for rest at night. Eyeroll.
Menstrual Phase (Winter – Your Period)
Day 1 of your cycle starts here. Both oestrogen and progesterone are at their lowest, which can leave you feeling tired, more sensitive, and craving rest – think hibernating for winter. The drop in oestrogen also reduces serotonin (your mood-boosting hormone), which can impact how you feel emotionally. Your body is shedding the uterine lining, and inflammatory resilience is at a low — so your body often craves warmth (hello hot water bottles), rest, and recovery.
Follicular Phase (Spring)
As your period ends, oestrogen begins to rise and so does your energy. You have clearer thinking, sharper focus, better mood, and more motivation. Follicle-stimulating hormone (FSH) is also doing its thing here, helping an egg mature. This is the point where you feel like you’re getting the spring in your step back: you're more sociable, switched on, and ready to go.
Ovulation (Summer)
Mid-cycle, oestrogen peaks and luteinising hormone (LH) triggers the release of an egg. This is your “hot girl summer” era — libido, strength, skin, and confidence are all at their best because oestrogen supports serotonin levels, collagen production, your metabolism, and heart health. This is when you feel your most magnetic-self and most you.
Luteal Phase (Autumn)
After ovulation, progesterone rises. It supports sleep, soothes the nervous system (via GABA), and prepares the uterus for a potential pregnancy — demanding more glucose and protein to be directed to the uterus lining (protein requirements may increase by ~10–12% during this time so it’s smart to prioritise whole foods like eggs, legumes, nuts, fish, or tofu, especially if training). But if fertilisation doesn’t occur, both progesterone and oestrogen levels begin to fall later on in this stage — and that hormonal drop is what can trigger PMS symptoms like mood swings, cravings, anxiety, bloating, and fatigue.
That moment each month when Oura tells you something’s up but you’ve done everything “right”
During the luteal phase, you might also notice your resting heart rate climbing, body temperature rising, and sleep quality dipping if you track with a wearable like Oura or Whoop. It’s easy to think, “What am I doing wrong?” — I’ve been there. But it’s likely that nothing is wrong. Instead, your hormones are shifting, and your body is working harder during this phase. The best thing you can do? Be kind to it. Give it what it needs — whether that’s rest, food, or a break from self-optimisation.
Why Do I Crave Sugar Before My Period?
During the later stages of our luteal phase, leading up to our period, our metabolism also speeds up slightly, increasing our energy needs. Appetite often increases, insulin sensitivity drops, and your sweet tooth may take over — this is down to lower FGF21 levels (a hormone that helps regulate metabolism) and a higher resting metabolic rate. So yes, you do actually burn more calories at rest in this phase — and you are hungrier (it’s not all in your head).
If you’re interested in satisfying your sweet tooth during this time, check out these double chocolate and raspberry cookies – packed with polyphenols (hello gut health), healthy fats (hormones are literally made from fat so don’t shy away from eating them!) and of course, chocolate (not that we need an excuse for this one, but it does contain happy-boosting compounds*, which can help lift your mood as oestrogen – and subsequently serotonin – dip).
*dark chocolate contains theobromine, a compound that mimics anandamine, which is a neurotransmitter that can make you happier.
Let’s Talk About Cycle Syncing
Cycle syncing is the idea that we should adjust our lifestyle (think: workouts, work demands, social plans, nutrition) around the different phases of our cycle. On paper, it makes sense. Our energy, mood, and metabolism fluctuate throughout the month, so syncing our routines with those changes feels intuitive, i.e., dialling things down during the luteal phase and leaning in during the follicular.
But here’s the thing: the actual scientific evidence is still limited (shocking, I know), and there’s far more nuance to it than the wellness world lets on. Just because we’re in the so-called “low hormone” phase (i.e., luteal) doesn’t mean we can’t hit a PB. In fact, elite athletes have won medals and broken records at every stage of their cycle.
Overall, current scientific reviews show only small, inconsistent differences in performance between phases. So, for my Pilates-going, matcha-drinking, recreational gym gals (I see you) — it’s likely your performance doesn’t meaningfully change whether you’re in the follicular or luteal phase.
Until more research comes our way, here’s my take: I don’t think cycle syncing should be about rigid rules. Instead, it’s best used as a tool for developing more self-awareness — learning to check-in and respond to how our body actually feels.
Take-home: if you feel like chasing a PB five days before your period – go for it. If you’d rather cancel plans and crawl into bed? That’s valid too.
Are My Hormones Imbalanced? Here’s How to Know
Hormone levels naturally fluctuate — that’s exactly what they’re meant to do. We wouldn’t want them to flatline or sit in some perfectly “balanced” state because hormones operate in complex, dynamic networks — the rise of one often triggers the fall (or rise) of another. So while “hormone balance” is something many of us are told to strive for on social media, the truth is: there’s no scientific definition for what that actually looks like.
So how do we know if our hormones are working as they should? Well, when something’s out of sync, your body will usually let you know. The key is learning to listen to our body.
First thing? Start tracking your symptoms. You don’t need a fancy app (though apps like Flo, Natural Cycles, and Clue can be helpful). Honestly, the Notes app on your phone works just fine. The goal is to track consistently — across 2–3 months — to allow you to spot patterns.
Some useful things to track: your mood (e.g. low, anxious, irritable, stable, joyful), energy levels (e.g. flat, wired, energised), sleep quality (how long you slept, how rested you felt), appetite and cravings, digestion (bloating, constipation, diarrhoea), skin changes (breakouts, oiliness, glow), exercise performance or motivation, sex drive, cycle symptoms (cramps, breast tenderness, headaches, PMS), and bleeding is particularly important (start and end date, heaviness, spotting).
If something feels consistently off each month, don’t ignore it. And please don’t self-diagnose using TikTok. Instead, speak to your GP. Ask questions and press for answers. Because your menstrual cycle is a vital sign — just like your blood pressure or heart rate. If your periods change — they become heavier, irregular, more painful — that’s your body waving a red flag.
Is It Just Me, or Are Periods Worse in Our 30s?
If you’ve noticed your periods changing as you’ve moved through your 30s, you're not imagining it. This was actually the reason I started tracking in the first place – when I hit my early 30s, my periods started becoming more intense, more emotional, more draining. Hormonal shifts can become more noticeable with age, and anecdotally, I’ve heard from countless women feeling “off” or hit harder by PMS than ever before. Instead of real answers, we’re often handed vague wellness trends — like seed cycling — as a magical solution.
But, in our 30s, life stress tends to peak — we’re juggling work deadlines, the London dating scene (or fertility spreadsheets), ageing parents, and not to mention the mental load of remembering everyone’s dietary requirements when hosting a dinner. All of this can disrupt hormonal signalling and amplify PMS symptoms.
And if you’ve recently come off hormonal birth control, that can add another layer. We often expect our cycles to “snap back” into place straight away — but in reality, it can take several months for hormones to recalibrate.
Seed Cycling: The Science
Seed cycling is a wellness trend where you eat specific seeds (flax and pumpkin in the first half of your cycle, sesame and sunflower in the second) to “balance” hormones. These seeds contain lignans, which may help modulate oestrogen levels by binding to excess oestrogen, along with zinc, selenium, and vitamin E, which are thought to support progesterone production.
There’s no solid scientific evidence that seed cycling regulates hormones. That said, incorporating more seeds into your diet is a great way to get in more fibre to support your gut health, and subsequently your gut-hormone connection (as explained in my previous post here).
How Stress Affects Your Hormones and PMS
So before we start spending a fortune on seeds — or stressing over which one we’re meant to eat on what day — we need to talk about the elephant in the room. Because here’s the thing: the more we add to our wellness to-do list, the more stressed we become. And that stress? It’s one of the biggest disruptors of hormonal health in the first place. Here’s why:
When consistently stressed, to keep up with the demand for high levels of cortisol, your body can “borrow” from the same building blocks used to make oestrogen and progesterone — a phenomenon often called the “cortisol steal.”
This throws off your hormones, worsening PMS symptoms and can contribute to heavier periods too. This can lead to:
Lower progesterone levels, which worsens PMS symptoms like anxiety, irritability, and sleep issues.
Oestrogen dominance, which can contribute to heavier periods, bloating, and mood swings.
Activation of the hypothalamic-pituitary-adrenal (HPA) axis, which can suppress the hypothalamic-pituitary-gonadal (HPG) axis — the system that regulates your reproductive hormones. This can lead to irregular cycles, worsened PMS, or even missed periods.
For a deep dive on how stress impacts hormone signalling, come to my upcoming Seed Talk on the gut-brain connection. Tickets available here.
So, what can we do without adding more to our to-do list?
Eating for Hormonal Balance: Why Your Gut Health Matters
When it comes to “eating for your cycle” or reducing PMS symptoms, it starts with your gut. I know you think I am being biased, but here me out.
Your gut microbiome — the trillions of microbes living in your digestive tract — plays a major role in regulating inflammation, immunity, and overall hormone health. Since many PMS symptoms (like bloating, mood swings, and fatigue) are inflammatory in nature, nurturing your gut is one of the smartest ways to ease them.
One gut-hormone link you should know about is the oestrobolome — a specialised group of gut bacteria that helps metabolise and regulate oestrogen (we went into this last week — see here). If your gut is out of balance, it can disrupt this process, leading to either oestrogen dominance or deficiency, both of which can worsen PMS.
To support your oestrobolome and overall gut health:
Eat more prebiotic-rich foods – think oats, garlic, onions, bananas and legumes. These feed your good bacteria.
Include fermented foods – like live yoghurt, kefir, kimchi, and kombucha for a daily dose of beneficial bacteria.
Get enough fibre – aim for 25–30g per day and stay hydrated to keep things moving and support healthy hormone elimination.
Consider a science-backed supplement – especially if you’re time-poor and always on the go. I love Myota for this (Code: DREMILY for 20% off)*.
TL;DR?
You’re not “crazy” for feeling like four different people a month — as your oestrogen and progesterone levels fluctuate throughout it, they impact your skin, mood, metabolism, and even your gut health. As such, your period is a powerful indicator of your overall health as a woman and it’s worth paying attention to it; tracking your symptoms over 2-3 months can help you spot patterns and know when something’s off.
When it comes to “hormone-balancing foods” and how to “eat for your cycle”, you don’t need to overcomplicate your wellness routine. If anything, adding more to your to-do list and subsequently becoming stressed is one of the biggest hormone disruptors. Start with prioritising your gut health to support your gut-hormone connection by focusing on fibre, fermented foods, and prebiotics (give seed cycling a miss for now – there’s no evidence behind it).
And just like that… wellness trends didn’t get the final word.
Let me know in the comments: Have your periods changed as you’ve gotten older? More intense? More emotional? Let’s chat — I have a hunch I might not be the only one experiencing this.
With love from London,
Dr. Emily, xo.
N.B. This content is for educational purposes only and isn’t a substitute for medical advice.
*Affiliate link - I earn a small commission at no extra cost to you.