Underweight with PCOS: Why "Just Don't Worry About It" Isn't Good Enough Advice

I was 16 when I got my diagnosis. I hadn't had a period — ever — so I was sent for an ultrasound, which confirmed cystic ovaries. PCOS. That was the word and then came the advice: "Don't worry about it unless you want to start a family one day".

That was it. No explanation of what was actually happening in my body. No mention of the fact that periods aren't just about fertility — they're a monthly report card on your overall hormone health. But, because I wasn't overweight, nobody seemed concerned. PCOS, in the eyes of the doctors I saw, was a "when you're ready for a baby" problem, not a "right now" problem.

If you've been told something similar — that your missing periods, your symptoms, your PCOS diagnosis can just sit on a shelf until it's "relevant" — I want to unpick why that advice is incomplete, and what was actually going on underneath it for me.

Slim, Busy, and "Fine"

From around 18, I worked in hospitality in Spain and Gibraltar — on my feet for hours, in the heat, constantly moving. I was naturally slim, active, and by every external measure, the picture of health. That's exactly why no one looked twice. Underweight and PCOS doesn't fit the picture most people (including some clinicians) have of the condition, which is so often talked about alongside insulin resistance and weight gain. So when you're slim, the assumption is that your hormones must be fine too. Mine weren't.

When Trying to "Heal" Made Things Harder

Later, while I was actually trying to get my periods back and support my hormone health, I fell into a lot of wellness-culture noise. Cut gluten. Cut dairy. Cut meat. Cut sugar. The advice was everywhere, and it all sounded reasonable in isolation. But stacked together, it made it genuinely difficult to eat enough — and made it even harder for my body to hold onto or gain any weight.

This is a pattern I now see constantly in the underweight-PCOS community: well-meaning restriction, often inspired by "clean eating" content, that ends up working directly against the thing you're trying to fix.

What's Actually Happening: Energy Availability and Your Hormones

Here's where the science comes in, in plain terms.

1. Your reproductive system is, in evolutionary terms, a luxury. If your body senses that energy coming in isn't reliably matching energy going out — through under-eating, over-exercising, high stress, or some combination of all three — one of the first systems it deprioritises is reproduction. This is sometimes described in research as low energy availability, and it can suppress the signalling between your brain and your ovaries (the hypothalamic-pituitary-ovarian axis) that needs to happen for a period to occur at all.

2. Now add PCOS into that picture. PCOS already involves a more sensitive, less predictable hormonal signalling system. So when you layer low energy availability — from restrictive eating, high activity levels, or chronic stress — on top of a PCOS-affected system, you can end up with a kind of double suppression. It's not "either PCOS or under-fuelling causes your missing periods" — for many of us, it's both, interacting with each other.

This is why "just eat more" as throwaway advice isn't wrong exactly, but it's not the whole story either. It's not about eating more in a vague sense. It's about whether your body is getting consistent, adequate, balanced nourishment to feel safe enough to switch reproductive function back on — while also managing the PCOS side of the equation.

The Turning Point: Covid, Research, and Rebuilding Differently

For me, the real shift happened during Covid, when I had time to actually research properly instead of chasing the next restrictive trend. What I found, again and again, was the same triad coming up:

• Nutritionally balanced meals — not restriction, but consistent, adequate intake across all the food groups I'd been avoiding.

• Weight training — building strength rather than depleting energy reserves through excessive cardio.

• Lower-intensity stress management — swapping high-intensity training for walking and yoga, to bring cortisol down rather than add to the load.

None of these are quick fixes, and none of them are a "cure" for PCOS — PCOS doesn't work that way for anyone. But rebuilding around consistent nourishment, strength-based movement, and lower cortisol gave my body the conditions it needed to start functioning differently. That combination is where my own periods, and my own health, genuinely began to turn a corner.

If This Is You

If you've been told not to worry, because you're not overweight, because your BMI looks "fine," because PCOS is being treated as a future-fertility issue rather than a current-health one — please hear this: you are allowed to take your symptoms seriously now, not just when you're ready to conceive.

If you're underweight and living with PCOS, it's worth having a conversation with a doctor or dietitian specifically about ene

rgy availability, not just PCOS in isolation — the two are deeply connected, and the right support looks different for an underweight body than it does for the version of PCOS that gets talked about most.

This post reflects my personal experience alongside general research on energy availability and hormonal health. It isn't medical advice — if you have PCOS and are underweight, please speak to your GP or a registered dietitian about your individual situation.

Fertility Support

£26.00

Buy Now