Why You Can't Lose Weight After 40 | Hormone Doctor Explains
Photo by Volodymyr Hryshchenko
If you're eating healthy, exercising regularly, and maybe even counting calories—but the scale still won't budge—you're not alone. And more importantly, it's not your fault.
As a double board-certified OB/GYN and Functional Medicine doctor who has worked with hundreds of women over 40, I can tell you with absolute certainty: the reason you can't lose weight after 40 has almost nothing to do with calories and everything to do with your hormones.
Why Everything Changed After 40
Your body at 40 is fundamentally different than it was at 30. And I don't mean that in a discouraging way—I mean let's finally understand what's happening so we can work with our bodies instead of against them.
Here's what's changed:
Your hormone production has shifted. Your ovaries are producing less estrogen and progesterone. Your stress response has likely been working overtime for years. And your thyroid may be slowing down.
Your muscle mass naturally decreases by about 3-8% per decade after 30. Since muscle is metabolically active tissue, losing it means your body burns fewer calories at rest.
Your insulin sensitivity often decreases, meaning your body doesn't handle carbohydrates and blood sugar the same way it used to.
But here's what's important: none of this means you're broken. It means you need a different approach.
The old "calories in, calories out" model completely ignores the hormonal reality of being a woman over 40. Your hormones control your metabolism, your hunger signals, where you store fat, and even how much energy you have to exercise.
The 3 Hormones Sabotaging Your Weight Loss After 40
When I work with women who are struggling with weight loss resistance, I always look at three specific hormones. When these hormones are out of balance, your body literally cannot burn fat—no matter how "clean" you eat or how hard you exercise.
These three hormones are:
Insulin – the fat storage hormone
Cortisol – the stress hormone
Thyroid – your metabolic thermostat
Each of these hormones plays a critical role in weight regulation, and when even one is out of balance, weight loss becomes incredibly difficult.
Why Insulin Matters for Weight Loss After 40
Insulin is your body's key that unlocks your cells to let glucose in for energy. But after years of processed foods, stress, poor sleep, and natural aging, many women over 40 develop insulin resistance.
When insulin is elevated, your body is in fat storage mode—not fat burning mode. This is why you can eat a low-calorie diet and still not lose weight.
Common signs of insulin resistancYour thyroid is your metabolic thermostat. It controls how fast or slow your body burns calories. e include:
Cravings for sugar and carbs, especially in the afternoon
Feeling shaky or irritable if you go too long without eating
Gaining weight around your belly
Feeling tired after meals
How Cortisol Affects Weight Gain After 40
Cortisol is your primary stress hormone, and chronic stress keeps cortisol elevated. High cortisol tells your body to store fat—especially around your midsection—because it thinks you're in survival mode.
Even worse, high cortisol steals progesterone (your calming, anti-anxiety hormone) to make more cortisol. This creates a vicious cycle of stress, anxiety, poor sleep, and stubborn belly fat.
Why Thyroid Function Is Critical for Metabolism
When thyroid function slows down (which is incredibly common in women over 40), your metabolism slows down with it.
You might be eating the same amount you always have, but now you're gaining weight because your body is burning fewer calories at rest.
Signs of sluggish thyroid function:
Unexplained weight gain or inability to lose weight
Constant fatigue, even after sleeping
Feeling cold all the time
Brain fog and difficulty concentrating
Thinning hair or hair loss
What You Can Do About Hormone-Driven Weight Gain
The good news? Once you understand what's happening with your hormones, you can take specific steps to rebalance them—and weight loss becomes possible again.
But it's not about eating less or exercising more. It's about:
Balancing your blood sugar to improve insulin sensitivity
Managing stress and supporting your adrenal glands to lower cortisol
Optimizing thyroid function with proper testing and targeted support
Eating in a way that supports hormone balance, not just calorie restriction
Moving your body in ways that support—not stress—your hormones
I break down all of this—including the exact steps you can take for each hormone—in my complete YouTube video.
👉 Watch the full video here: Why You Can't Lose Weight After 40 (Fix These 3 Hormones First)
You're Not Broken—Your Body Just Needs a Different Approach
I lived this myself. After a back injury in 2012, my body stopped responding the way it used to. I was doing everything "right," but nothing worked. Conventional medicine had no real answers—just "eat less, move more."
But that wasn't the problem. And it's probably not your problem either.
That's what led me to functional medicine—and it's exactly how I help women every single day finally break through weight loss resistance and feel like themselves again.
Your body isn't broken. It's just speaking a different language now. And once you understand what it's trying to tell you, weight loss becomes possible again—without restriction, without extremes, and without fighting your body every step of the way.
Ready for Personalized Support?
If you're dealing with stubborn weight gain, fatigue, brain fog, or other hormone-related symptoms, and you're ready for more than general advice, I can help.
In my functional medicine practice, I work with women over 40 to:
Identify the root causes of weight loss resistance through comprehensive testing
Create personalized protocols based on YOUR unique hormone profile
Provide ongoing support and guidance so you finally see lasting results
Schedule a FREE Hormone Health Strategy Call and let's create a clear roadmap for what YOU need to finally lose weight and feel amazing again.