Your Metabolism Isn’t Broken. It’s Under-Muscled.

We’ve been told for years that metabolism slows with age, or that midlife weight gain and energy decline is inevitable.

But that’s not totally true: if you’re feeling those effects, it’s likely that your metabolism isn’t actually bad or broken. It’s just under-muscled.

What we call a “slow metabolism” or “bad metabolism” is more often the result of lost lean muscle mass, diminished strength, and declining mitochondrial function (not the aging process itself), and these are all things you can improve.

Defining Metabolism

Let’s dig into what “metabolism” encompasses, because it isn’t just about burning calories. “Metabolism is all of the chemical processes your body uses to turn food into energy, power your cells, and keep you alive,” says Dr. Sita Kedia, functional medicine physician at PALM Health. “At its core, metabolic health is about how efficiently and resiliently your body produces and uses energy.”

When it’s working well, you experience:

• Stable blood sugar and better insulin sensitivity
• Healthy muscle mass and strength (both a driver and a reflection of strong metabolic health)
• Healthy cholesterol levels and less inflammation in the body
• Sustained energy and faster recovery
• Lower risk of diabetes, heart disease, and cognitive decline

In short, when we talk about “improving metabolic health”, we’re talking about building a state of long-term energy, efficiency, resilience, and vitality in the body.

It All Starts with Muscle

Muscle is one of your most metabolically active tissues, and it forms the basis of a healthy metabolism. Here’s how:

1. Muscle uses more energy at rest than fat tissue does (a major contributor to your resting metabolic rate). So, the more muscle you have, the more calories you burn at rest.
2. Muscle stores and burns glucose efficiently, improving blood sugar regulation and insulin sensitivity. 
3. Muscle cells are rich in mitochondria, which are the energy-producing engines inside your cells. You may notice that with more lean muscle mass on your body, your energy levels improve.

According to Dr. Kedia, the catch is this: “As we age, we naturally lose muscle—especially women during perimenopause—unless we actively maintain or build it. This loss, known as sarcopenia, often masquerades as a ‘slowed metabolism.’ But in fact, starting by building lean muscle mass can do wonders for your metabolism.”

Muscle mass and strength aren’t only the directors of your metabolism. They’re also some of the clearest indicators of how well you’ll age.

Try these quick self-assessments:

• Grip strength test: Use a hand dynamometer, or simply squeeze your own hand hard and notice how much force you can apply.
• Step test: Time yourself walking up a flight of stairs or stepping on and off a low bench. Can you do it for 2 minutes?
• Sit-to-stand test: From a chair, stand up and sit down repeatedly for 30 seconds. How many reps can you complete?

These self-tests can help you see how your muscles, heart, and mitochondria are performing together, and give you a baseline understanding of where your strength is now and how you can improve.

“If you feel like your metabolism has stalled or is declining, if you’re in your 40s or above, or if you’re a woman approaching menopause, it’s time to pick up the weights,” says Dr. Kedia.

Building strength protects your muscle, restores mitochondrial function, and improves how your body uses energy. It’s one of the most powerful levers you can pull for your long-term health.

Start with small, sustainable steps:

• Add resistance or weight training 2–3 times a week
• Prioritize protein in every meal to support muscle repair (roughly 100g of protein daily for most adults)
• Focus on sleep quality and stress management, both of which influence metabolic function

Your metabolism isn’t failing you. It just needs more muscle. Skip the fad diets and start training for energy, resilience, and strength— and if you still notice metabolic sluggishness, fatigue, weight gain, or other symptoms, your physician can help you dig deeper to find out what’s going on.