Why You Might Feel Worse on a Low-Carb Diet with PCOS

If you’ve ever been told to “just cut carbs” to manage your PCOS, you're in the right place. Many women I work with arrive frustrated, having already tried a low-carb diet, keto, or sugar detox, only to feel worse: tired, moody, bloated, or stuck at the same weight.

So why does this happen? And is going low-carb really the best approach for PCOS?

In this post, we’ll look at:

• Why low-carb diets may backfire in PCOS

• The link between blood sugar, cortisol and hormone imbalances

• Signs your body isn’t coping with too few carbs

• What to do instead for long-term hormone and weight balance

The Low-Carb Hype and PCOS

Low-carb diets are often marketed as a quick fix for PCOS weight gain and insulin resistance. There’s no doubt that managing blood sugar is important. But for many women with PCOS – especially those who’ve recently come off the pill, are trying to get their cycle back, or are already dealing with fatigue, irregular eating, or under-fuelling, ultra-low-carb eating can create more problems than it solves. Try my Off the Pill with PCOS Guide for more tips here.

PCOS is a complex, whole-body condition. It’s not just about carbs or calories – it’s about how your metabolism, hormones, immune system, gut, and stress response interact. Carbohydrates, when used wisely, play a vital role in keeping that system in balance.

Why You Might Feel Worse on a Low-Carb Diet with PCOS

Here’s what might be going on under the surface:

1. You’re Running on Stress Hormones

When you eat too few carbohydrates, your body may increase cortisol (your main stress hormone) to keep your blood sugar stable. Cortisol is designed to help you survive a crisis, but chronically high levels can:

• Disrupt ovulation and progesterone

• Worsen inflammation

• Increase cravings later in the day

• Make weight loss harder, not easier

This is especially important if you’re already feeling wired-but-tired, skipping meals, or dealing with blood sugar crashes. In these cases, a very low-carb approach adds fuel to the fire. Read more about how stress affects hormone balance in this post.

2. You’re Already Undereating Without Realising

Many women with PCOS unintentionally under-eat – especially after years of trying to lose weight, skipping breakfast, or relying on caffeine to get through the day.

If you then remove most of your carbs, your overall calorie and nutrient intake can drop too low, making it harder for your thyroid, metabolism, and cycle to function properly.

Low energy, hair thinning, irregular periods, feeling cold or sluggish are all signs your body may not be getting enough fuel, and cutting carbs further can make this worse.

3. You’re Missing Out on Key Nutrients

Carbohydrates aren’t just about energy. Whole food carb sources like root vegetables, oats, pulses, fruit, and whole grains provide essential nutrients for hormone function, gut health, and ovulation – including:

• Magnesium (helps with insulin sensitivity and mood)

• B vitamins (support energy, metabolism, and hormone clearance)

• Fibre (feeds gut bacteria and improves oestrogen metabolism)

• Antioxidants (reduce inflammation and support egg quality)

Cutting carbs often means cutting these nutrients too, which can leave your body struggling to repair and rebalance.

4. It’s Not Sustainable

Let’s be honest, most low-carb plans aren’t realistic long term. They often lead to a cycle of restriction, intense cravings, and binge eating. That “on-off” pattern can drive insulin spikes, worsen inflammation, and make you feel like you’re failing, when in fact, your body just needs better support.

You don’t have to be perfect. You just need to be consistent. And that means finding a way of eating that supports your blood sugar and your lifestyle.

Signs You’re Not Thriving on a Low-Carb Diet

If you’re doing low-carb and noticing any of the following, it might be time to rethink your approach:

• Fatigue or brain fog, especially mid-morning or mid-afternoon

• Waking in the night or early morning

• Irritability, low mood or anxiety

• Constipation or bloating

• Low or irregular periods

• Increased cravings for sugar or carbs in the evening

• Stalled weight loss despite “doing everything right”

If you are struggling with cravings for sugar and carbs, try my 7 day PCOS Sugar Reset here.

What to Do Instead: A Balanced Approach for PCOS

Balancing blood sugar doesn’t mean cutting out all carbs. It means using them wisely.

Here’s how to support your hormones without triggering a stress response:

1. Build Balanced Plates

Aim for:

• Protein (20–30g) at each meal

• Healthy fats (olive oil, seeds, avocado)

• Colourful fibre-rich veg or salad

• A sensible portion of slow carbs (½ to 1 cup cooked): e.g. sweet potato, quinoa, oats, lentils, wild rice

This gives your body fuel and stability – so you avoid spikes, crashes, or cravings. More 30g protein meal ideas here, or breakfast ideas here.

2. Front-Load Your Carbs

Eating a moderate portion of slow-digesting carbs at breakfast and lunch can help regulate cortisol and reduce stress-driven hunger later. This also supports ovulation and cycle repair, especially if you’re trying to restore your periods or prepare for pregnancy. You can learn more about the signs of ovulation in this post.

3. Focus on Food Quality Over Quantity

Ditch ultra-processed foods, but don’t fear real, whole carbs. Some of the best PCOS-friendly options include:

• Cooked oats or buckwheat

• Sweet potatoes or butternut squash

• Berries, apples, pears

• Legumes and lentils

• Quinoa, brown rice, or wild rice

• Root veg like parsnips or carrots

4. Avoid Skipping Meals

Regular meals keep blood sugar stable, support metabolism, and reduce the need for your body to rely on stress hormones for fuel. Here are 5 nutrition tips to support your metabolism.

Final Thoughts

Low-carb diets may feel like the ‘right’ answer – especially when you’re desperate for change. But if you’ve already tried cutting carbs and you’re still struggling with fatigue, cravings, or hormone symptoms, it may be time for a different approach.

Food-first, functional nutrition for PCOS doesn’t mean extreme restriction. It means understanding what your body needs, and giving it the right support at the right time.

For a comprehensive overview of PCOS diagnosis, underlying mechanisms, and updated clinical recommendations, the 2018 International Evidence-Based Guideline for the Assessment and Management of PCOS by Teede et al. is a key resource for practitioners and researchers alike. Read the full guideline here.

Want help building a realistic food plan that works for your PCOS type?

I am a BANT registered nutritionist and health coach, specialising in PCOS support. i work online with women locally in Manchester and across the UK.

My 12-Week PCOS Hormone Shift Method is designed to help you restore hormone balance, reduce inflammation and support weight and cycle health – without extreme diets or guesswork.

• Explore the 12-week PCOS Programme here.

• 4-week mini programmes here.

If you have PCOS and are moving into your late 30s or 40s, my PCOS and perimenopause guide covers how hormone changes at this stage can affect symptoms, weight, and overall health, plus practical ways to support your body during the transition.

Disclaimer: The information provided is for educational and informational purposes only and should not be considered medical advice. While I provide guidance based on my expertise as a registered nutritionist and health coach, all health-related decisions should be made in consultation with your healthcare provider. Any changes to medication, supplements, or treatment plans should only be made under the supervision of a qualified medical professional. The suggestions outlined are intended to support general well-being and do not replace medical treatment or diagnosis. Always consult a healthcare professional before making significant lifestyle or dietary changes.

Updated August 2025 to reflect PCOS research and nutrition strategies.