Is perimenopause making you gain weight? Probably.
If you suddenly gained weight in your late 30s or 40s without any obvious change in your diet or exercise, it’s probably because of perimenopause. Sudden weight gain in perimenopause is common, but fixable. We just need a new plan that takes into account your evolving hormones.
January 29, 2025
Perimenopause tanks your metabolism and makes you gain weight. True story.
If you’ve hit your late 30s or 40s and suddenly feel like your body is playing by a completely different rulebook—welcome to perimenopause. I know, it’s the worst welcome party ever. You’re doing all the same things you used to do to maintain your weight, but now? The scale is creeping up, your midsection feels like it’s got a mind of its own, and nothing seems to work anymore.
And before you start blaming yourself (or your favorite carbs), let’s talk about what’s really going on with your metabolism—because this is NOT just a “calories in, calories out” situation (seriously, let’s retire that nonsense).
The perimenopause weight puzzle
"I'm eating the same but gaining weight."
“I rapidly gained 10-15 pounds when I turned 40”
"I cut carbs, I exercise, but my belly won’t budge."
"My husband and I went on the same diet—he lost 15 lbs, I gained 3. WTAF?"
Sound familiar? That’s because perimenopause and weight go hand in hand, and it’s not just about what you’re eating or how much you’re moving. Your hormones are shifting in ways that directly impact how your body stores and burns fat.
Estrogen, insulin, and why your waistline is expanding
Let’s talk estrogen—because she’s been doing a lot of behind-the-scenes work for you, and now she’s ghosting.
We can blame fluctuating estrogen for those night sweats, mood swings, hot flashes, and those heavy perimenopausal periods.
One of the lesser known estrogen jobs is her help in keeping insulin working efficiently. When estrogen is stable, your body processes carbs more effectively, which makes weight management easier.
During perimenopause, estrogen starts going up, dow and sideways (and eventually declines), making you more insulin resistant. That means:
You gain weight more easily (especially from carbs)
You crave sweet stuff
Your blood sugar swings wildly, leading to energy crashes and mood swings
And if that wasn’t enough, weight loss after 40 is also impacted by:
Natural muscle loss after 35 (about 4-6 lbs per decade if you’re not strength training)
Lower testosterone (which makes it harder to build and maintain muscle)
Higher cortisol from stress & poor sleep (hello, belly fat)
Possible thyroid slow-down (which can tank metabolism even further)
So no, you’re not crazy. Your body has changed. And it needs a new strategy.
Why your old diet tricks aren’t working
Remember when you could just cut calories, skip carbs, or do a little intermittent fasting, and the weight would drop? Yeah… not anymore.
Why? Because “is perimenopause making me gain weight?” is a real question with a real metabolic shift behind it. Instead of responding to exercise and caloric restriction by burning fat, your body now sees it as a stressor and holds onto fat even harder.
Slashing calories too low? Yikes there must be a famine. Let’s slow metabolism even more.
Skipping meals? Wrecks blood sugar, triggers cravings, makes you feel awful.
Only doing cardio? Not enough to rebuild lost muscle, which is what actually burns calories at rest.
Read next:
What actually works for perimenopausal weight loss
Prioritize protein
Aim for 100g per day (about 25-30g per meal)
Include protein with every meal and snack
Focus on high-quality sources like eggs, fish, meat, and legumes
More protein = better muscle retention = higher metabolism = fewer cravings.
Time your carbs strategically
Don’t go zero-carb
Pair carbs with protein & healthy fats to blunt blood sugar spikes
Eat carbs around workouts or earlier in the day
Focus on complex, fiber-rich carbs (sweet potatoes, quinoa, beans, whole grains)
Managing carbs wisely prevents insulin resistance from getting worse.
Build muscle, boost metabolism
Strength train 2-3x per week
Focus on compound movements (squats, deadlifts, pushups—big moves that build more muscle)
Don’t fear getting “bulky”—muscle is your metabolic GOLD and works like built in Spanx
More muscle = higher resting metabolism = easier perimenopause fat loss.
Balance blood sugar
Eat regular meals (don’t skip breakfast!!)
Include protein, fat, and fiber at every meal
Watch portion sizes of refined carbs & sugar
Stable blood sugar = fewer cravings, better energy, and less stress on metabolism.
Get tested
Your symptom (like weight gain) tells us the what.
Proper lab testing tells us the why and the how. Looking under the hood to understand what markers are off, what systems need adjusting and what your hormones are actually doing is critical to getting ahead of perimenopause weight gain, and help you actually lose weight.
The lab work you actually need
Full thyroid panel (not just TSH—include Free T3, Free T4, Reverse T3)
Fasting insulin & blood sugar (to check for insulin resistance)
Inflammation markers
Sex hormones (estrogen, progesterone, testosterone)
Cortisol patterns (to see if stress is driving weight gain)
Key nutrients (vitamin D, B12, iron, magnesium)
We run each of these tests and more for Motherwell patients.
Beyond the scale: it’s about more than weight
This isn’t just about fitting into your jeans. These metabolic shifts affect:
Energy levels
Mood stability
Sleep quality
Long-term health risks (diabetes, heart disease, osteoporosis)
Your body isn’t broken
Instead of fighting your hormones with extreme diets & over-exercising…
Eat enough of the right foods
Lift heavy things
Manage stress & sleep
Get the right tests
Support your hormones (instead of punishing them)
Want help navigating perimenopause and weight without losing your mind (or metabolism)? Check out my Perimenopause Party program, where we ditch the BS and make your hormones work for you, not against you.
Let’s make perimenopause and weight loss after 40 suck less. You in?
xo
Alison
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