How to Boost Your Metabolism?

"Boosting your metabolism" is one of the most heavily marketed ideas in fitness — and one of the most misunderstood. Here is what metabolism actually is, what genuinely influences it, and what to ignore.

What is metabolism?

Metabolism describes all the chemical processes that keep you alive — converting food into energy, building and repairing tissue, and clearing waste. When people talk about a "fast" or "slow" metabolism, they usually mean total daily energy expenditure, which has four components:

Basal metabolic rate (BMR) — energy used at complete rest. This is the largest share, typically around 60–70% of the total.
Thermic effect of food — energy used digesting and absorbing what you eat, around 10%. Protein has the highest thermic effect.
Exercise activity — deliberate training.
Non-exercise activity thermogenesis (NEAT) — everything else: walking, fidgeting, standing, household tasks. This varies enormously between individuals and is often larger than deliberate exercise.

What actually influences your metabolic rate

Body size and composition. The biggest factor by far. Larger bodies need more energy, and muscle tissue is more metabolically active than fat.
Age. Metabolic rate declines with age, though research suggests this happens later and more gradually than commonly assumed — much of the mid-life slowdown is really lost muscle and reduced activity.
Sex. Men typically have higher BMR, largely due to greater muscle mass.
Genetics. Real, but a smaller factor than most people assume.
Thyroid function. An underactive thyroid genuinely lowers metabolic rate — and is treatable, which is why it is worth checking if you are struggling.

Cardio or weights?

This is a long-running debate, and the honest answer is that they do different things.

Resistance training builds muscle, and muscle raises resting energy expenditure. The effect per kilogram is smaller than fitness marketing suggests, but it compounds, and crucially resistance training preserves muscle during weight loss — which protects your metabolic rate when it would otherwise fall.

Aerobic exercise burns more energy during the session itself and produces strong cardiovascular and metabolic health benefits.

Small studies have looked at hormonal responses to each — including FGF21, which is involved in energy metabolism — and found differences between cardio and weight training. These are interesting but preliminary: single sessions in small groups of participants tell us little about long-term outcomes.

The practical answer is to do both. They are complementary, not competing.

What genuinely helps

Build and keep muscle — resistance training at least twice a week
Eat enough protein — supports muscle retention and has the highest thermic effect
Move more overall — increasing NEAT is often more impactful than adding another gym session
Sleep properly — poor sleep disrupts appetite hormones and reduces spontaneous activity
Avoid severe restriction — aggressive dieting reduces metabolic rate and costs you muscle

What does not work

Metabolism-boosting supplements, detox teas and "fat-burning" pills do not meaningfully change energy expenditure. Green tea, chilli and caffeine have measurable but very small and short-lived effects — nowhere near enough to matter. Eating six small meals rather than three does not raise metabolic rate; total intake is what counts.

When to get checked

If you are gaining weight despite no change in diet or activity, or experiencing persistent fatigue, cold intolerance, hair thinning or low mood, ask your GP about thyroid function. An underactive thyroid is common, easily tested and readily treated.

Checking your markers

Rightangled's home blood tests can assess thyroid function, HbA1c, iron and vitamin D — all of which affect energy and metabolism. Our DNA tests examine markers relating to metabolism and exercise response. Results are reviewed by our clinical team, which includes GPhC-registered independent prescribers, with medical oversight from our doctor, Dr Abdullah.

Verify us with the General Pharmaceutical Council (registration 9011933), see our LegitScript certification, and read reviews on Trustpilot.