Metabolism: how it works and what affects it

Metabolism is the set of processes your body uses to turn food and drink into the energy it needs to function. It's working constantly — to keep your heart beating, your lungs breathing, your brain active, and your cells maintained — not only when you're moving around.

This guide focuses on what the evidence supports and steers clear of quick-fix claims, of which there are many in this area.

What "metabolic rate" means

Your basal metabolic rate is the energy your body uses just to keep its essential functions running at rest. For most people, this resting energy use accounts for the largest share of the energy they burn each day — more than exercise does for the typical person.

What actually affects it

Several things influence how much energy your body uses, including:

• Body size and composition — larger bodies, and bodies with more muscle, tend to use more energy at rest.
• Age — energy needs generally change across the lifespan.
• Activity — movement of all kinds adds to the energy you use.

What the evidence doesn't support

There's no single food, drink, or supplement that reliably and meaningfully "boosts" your metabolism in a way that transforms your health or weight. Claims promising to do so usually overstate small, short-lived, or insignificant effects. The dependable foundations remain regular movement, enough good-quality sleep, and a balanced way of eating.

This page replaces a former commercial page at this address with general, evidence-based information. If you want advice tailored to you, a doctor or a registered dietitian is the right place to go.