The Truth About Metabolism After 40 (It’s Not What You Think)

Written by: Lindsay Little, MS — Holistic Health Coach

If you’ve been told your metabolism is slowing down just because you’re getting older—I have good news. That’s not the full story. And no, you’re not broken.

Let’s bust a myth real quick: It’s not your age that’s making it hard to lose weight.

It’s your muscle mass.

That’s right. Your metabolism isn’t just fading into the sunset because you hit 40, or because you’ve had kids, or because menopause is knocking at your door. What’s really happening? You’re losing muscle.

The Metabolism Myth

We’ve been told for decades that metabolism just naturally tanks with age. Sure, you don’t have the metabolism of a 13-year-old anymore (wouldn’t that be nice?). But that doesn’t mean you’re doomed to carry extra weight forever.

The truth is, women start to lose muscle mass at a rate of 3-8% per decade after age 30. This process speeds up even more after 60. It’s called sarcopenia, and it’s a natural part of aging. But natural doesn’t mean inevitable.

And here’s the deal: Muscle drives metabolism.

More muscle = faster metabolism. Less muscle = slower metabolism.

So no, your metabolism isn’t mysteriously vanishing. You’re just not supporting your muscle mass the way your body needs as you get older.

Why You’re Losing Muscle (And How to Fix It)

Two major factors drive muscle maintenance and growth:

1. Protein intake

2. Strength training

Let’s break it down:

1. Protein is non-negotiable.

When you cut calories or go on a diet, one of the first things that usually drops? Protein. That’s a problem.

Protein provides the building blocks your body needs to repair muscle and build it back stronger. Without enough protein, your body has nothing to work with.

Plus, if you’re not eating enough protein during a weight loss phase, the weight you lose is more likely to come from muscle, not fat. That’s the opposite of what we want.

2. Strength training is essential.

Many women avoid lifting weights because they worry it will put pressure on their bones and increase the risk of a fracture. Here’s the wild truth: that’s the point.

When you put load-bearing stress on your muscles and bones, it signals your body to break them down and then rebuild them—stronger. It sounds scary, but it’s not. It’s just not something your doctor ever explained to you. This is how we build both muscle and bone density. It’s also one of the best ways to prevent osteoporosis.

Those little micro-tears that happen during weight lifting? That’s where the magic happens. When you rest and refuel, your body repairs and strengthens what you just worked. And a reason why rest days are SO important.

Why Calorie Deficits Can Backfire

A lot of women come to me saying they’re eating 1200 calories a day and still not losing weight. Sound familiar?

Here’s what’s happening: your body thinks it’s starving.

When you chronically under-eat, your body shifts into survival mode. It holds onto fat and slows down non-essential functions. That includes metabolism.

To truly lose fat (and not muscle), you need a moderate calorie deficit and a high-protein, strength-focused plan.

I usually recommend:

- No more than a 25% calorie cut

- A cut phase lasting 6-8 weeks

- Adequate protein intake to preserve muscle

This isn’t forever. It’s a phase. And during this phase, the goal is to maintain muscle while burning fat. Not build muscle. Not break yourself. Just preserve what you’ve got.

Once your cut is complete, you can slowly return to maintenance calories and then think about building more muscle if that’s your goal (which will require you to eat above your maintenance calorie budget).

Recap: Your Metabolism Isn’t Broken. But Your Muscle Might Be.

If you want a healthy metabolism, you need healthy muscle.

Here’s how to get there:

- Eat enough protein

- Lift heavy (with good form)

- Avoid long-term, aggressive calorie deficits

- Work with someone who can help you calculate your energy needs for fat loss, maintenance, and muscle gain phases

Remember, your body won’t lose fat if it doesn’t have the resources to survive. Fat storage is a safety net. And your job is to show your body that it’s safe to let it go.

Ready to Take Action?

If you’re ready to ditch the myths and get a plan that actually works for your body, I’d love to invite you to my free, private, off-social community: The Glow Lounge.

It’s a chill space for women who are ready to reclaim their energy, health, and favorite pair of jeans—without judgment or BS.

This is where your glow-up begins. ✨

Let’s build muscle, boost metabolism, and feel really good again—together.

Hey there! I’m Lindsay! I’m a Holistic Health Coach with a Master's Degree in Holistic Nutrition and a specialization in gut health. In my virtual health coaching practice, Full Bloom Acres Wellness, I help busy women over 40 eat the foods they love without embarrassing, painful, and annoying digestive issues. I would love to help you, too! Connect with me on social media at @fullbloomacres or on my website, www.fullbloomacres.com. 

Ready to take control of your hormones and feel like YOU again? Join my FREE community, The Glow Lounge—a chill space for women ready to reclaim their energy, health, and favorite pair of jeans. The Glow Lounge is where your Glow-Up begins. Click here to join!

DISCLAIMER: This information is for educational and informational use only and is not meant to diagnose or treat disease or illness. Please work with a qualified healthcare practitioner before making dietary or lifestyle changes.