Insulin Resistance: Why Fat Loss Slows in Perimenopause & Menopause

1 day ago

3 min read

By Sayuri Barritt RD, 10/4/26

You've done everything right. You learned that losing fat means staying in a calorie deficit, so you weigh your portions, log every meal, and show up for workouts, even on the days you're exhausted. It worked in your 30s.

But lately, your waistband feels tighter, and the extra weight keeps settling around your middle. You're doing more than ever, yet your body isn't responding.

It feels like a hamster wheel: endless effort, no answers. And no, it's not something wrong with your body. For many women in perimenopause and menopause, a hidden factor called insulin resistance may be part of the story.

Woman enjoying a balanced sandwich to keep her blood sugar and energy steady.

What Is Insulin Resistance?

You've probably heard the term "insulin resistance" and know it has something to do with blood sugar. Here's the simple version.

When you eat carbs, like bread, rice, or fruit, your body turns them into sugar, and your insulin level rises in response. Insulin's job is to bring your blood sugar back down to a normal level. It works like a key, unlocking your muscles so that sugar can move out of your blood and fuel your day. Whatever your muscles don't need gets stored as fat for later.

With insulin resistance, your muscles stop listening to that key, so they take in less sugar. Your body makes more and more insulin, but that sugar still has to go somewhere, so more of it gets directed to fat storage, often around your belly. That's why fat loss can slow down, even when you're in a calorie deficit (eating a bit less than your body burns).

The tricky part? It's especially common during the hormonal shifts of perimenopause and menopause, yet many women never find out. That's because routine blood tests often look normal for years, since your body is working overtime behind the scenes to keep your blood sugar in check.

Why It Shows Up Now

Estrogen helps your body respond well to insulin. As it drops during perimenopause and menopause, your muscles become less responsive, and more sugar gets stored as fat.

We also naturally lose muscle with age, leaving less room to store that sugar. Add poor sleep and midlife stress, and blood sugar becomes even harder to manage.

That's why the calorie deficit that worked in your 30s may not work the same way now. Your body has changed, so your approach needs to change too.

How to Check for Insulin Resistance

Since routine blood sugar tests can look normal even when you have insulin resistance, a simple calculation called HOMA-IR can give you a clearer picture. It uses two numbers from a fasting blood test (usually after 8 to 12 hours without food):

Fasting insulin (not part of routine bloodwork, so ask your PCP for it)
Fasting blood glucose (blood sugar)

Then plug them into this formula:

HOMA-IR = (fasting insulin × fasting glucose) ÷ 405

(This formula uses insulin in µIU/mL and glucose in mg/dL, the standard US units.)

For example, if your fasting insulin is 10 and your fasting glucose is 90:

(10 × 90) ÷ 405 = 2.2

What your number may mean:

Healthy range: around 1.0 (0.5–1.4)
Less than 1.0: you're insulin-sensitive, which is optimal
Above 1.9: early insulin resistance
Above 2.9: significant insulin resistance

Bring your results to your doctor, who can help interpret them alongside your health history.

How Nutrition Can Help Improve Insulin Resistance

What you eat, and even the order you eat it in, can make a big difference in how your body handles blood sugar.

Try this: eat your veggies and protein first. At your next meal, start with the vegetables and protein on your plate, and save the carbs, like rice, bread, or potatoes, for last. Research shows this simple switch can lead to a smaller blood sugar spike, which means your body needs less insulin and you stay fuller longer.

Take Back Control of Your Fat Loss

If your fat loss has slowed in perimenopause or menopause, it's not because you're doing it wrong or not trying hard enough. Your body has changed, and with the right approach, it can start responding again.

Understanding insulin resistance is the first step. Knowing your numbers, eating in a way that stabilize your blood sugar, and making small, consistent changes can help your calorie deficit work for you again.

If you're ready for more guidance, join my live, monthly Blood Sugar Blueprint class, where you'll learn: