Gaining Weight Despite Eating Less and Working Out?
If you're eating less, working out more, and still gaining weight, you're not crazy and you're not doing anything wrong. This is one of the most common and frustrating experiences I hear from women in my practice — and it has a clear biological explanation.
During perimenopause, your body's relationship with insulin, cortisol, and oestrogen changes fundamentally. Oestrogen normally helps your body store fat in a healthy distribution (hips and thighs). When oestrogen drops, your body shifts to storing fat around your midsection — the same pattern seen in men, driven by insulin and cortisol.
This means that the strategies that worked in your 30s — eating less, doing more cardio — can actually backfire. Caloric restriction increases cortisol. Excessive cardio increases cortisol. And cortisol, combined with low oestrogen and insulin resistance, tells your body to store belly fat.
The insulin resistance factor
As oestrogen drops, your cells become less responsive to insulin. This means that the same amount of carbohydrates you used to handle fine now causes higher blood sugar and more fat storage — particularly around your belly.
Insulin resistance doesn't mean you have diabetes. It means your body is less efficient at processing carbohydrates, and it compensates by producing more insulin. High insulin levels signal your body to store fat, especially visceral fat around your organs.
This is why you can eat less and still gain weight. If your insulin is high, your body is in storage mode regardless of how many calories you eat. The composition of those calories matters more than the quantity.
Why more cardio makes it worse
Chronic cardio elevates cortisol. Cortisol and insulin together are a recipe for belly fat storage — especially when oestrogen is low. This is why women who double down on running or spinning often see their weight go up, not down, during perimenopause.
The answer isn't to stop exercising. It's to change the type. Strength training builds muscle, and muscle is metabolically active tissue that improves insulin sensitivity. A woman who strength trains 3-4 times per week will burn more calories at rest and process carbohydrates more efficiently than a woman who does only cardio.
What actually works for perimenopause weight
Prioritise protein. Aim for 1.2-1.6 grams of protein per kg of body weight per day. Protein stabilises blood sugar, reduces insulin spikes, and preserves muscle mass — all critical during perimenopause.
Lift weights 3-4 times per week. This is the single most effective change you can make. It improves insulin sensitivity, builds metabolically active muscle, and counteracts the muscle loss that accelerates after 40.
Reduce refined carbohydrates, not total calories. Focus on protein, healthy fats, and vegetables. Carbohydrates aren't the enemy, but refined carbs drive insulin spikes that your perimenopause body can't handle as well as it used to.
Consider berberine. Some studies suggest berberine (500mg, 2-3 times daily) can improve insulin sensitivity comparable to metformin. Discuss with your doctor, especially if you have any medical conditions.
Want to know what's really going on in your body?
Take the free Hormone Scan. It maps your exact symptoms to your hormonal profile and tells you precisely where to start.
Frequently Asked Questions
Why am I gaining weight even though I eat less and exercise?
During perimenopause, dropping oestrogen causes insulin resistance and shifts fat storage to your belly. Caloric restriction raises cortisol, and excess cardio raises cortisol further. High cortisol + high insulin + low oestrogen = belly fat, regardless of calories.
Is insulin resistance causing my weight gain?
It's very likely a contributing factor. As oestrogen drops, your cells become less responsive to insulin, causing your body to produce more insulin. High insulin signals fat storage, especially visceral belly fat. This is why what you eat matters more than how much you eat.
Should I do cardio or weights during perimenopause?
Strength training is more effective than cardio for perimenopause weight management. It builds muscle (which improves insulin sensitivity), while excessive cardio raises cortisol and can worsen belly fat. Aim for 3-4 strength sessions per week, with some moderate cardio for heart health.