Can You Really 'Boost' Your Metabolism?

Metabolism is the term used for the series of chemical reactions that take place in the body as cells break down food and drinks and convert it into energy.

The promise of a metabolic boost, is a common claim in the wellness space. Green tea, chilli, cold showers, small frequent meals, apple cider vinegar as just a few on the list of alleged metabolism boosters. The list is long, the evidence is considerably shorter, and the gap between the two is reliably filled with confident marketing.

So what does the science actually say?

What Metabolism Actually Means

Metabolism refers to all the chemical processes in the body that sustain life. This includes converting food into energy, repairing tissue, growing, and removing waste from the body. When people describe their metabolism as being fast or slow, this is often referring to our metabolic rate (the rate at which the body uses energy to maintain essential functions).

That energy use breaks down into a few pieces:

Resting metabolic rate (RMR) - what the body burns simply existing. These basic functions include: breathing, blood circulation, keeping organs running. This is roughly 60-70% of most people’s daily burn, and it's what most people are referring to when they talk about metabolism.

The thermic effect of food (TEF) - the energy cost of digesting food. Accounts for roughly 10% of your daily total energy expenditure.

Exercise activity thermogenesis (EAT) - energy burned during physical exercise.

Non-exercise activity thermogenesis (NEAT) - energy burned through all movement that isn't deliberate exercise: walking, fidgeting, standing, doing housework. This is more variable than most people realise and can range massively.

So people talk about "boosting metabolism," they're almost always talking about RMR. RMR is driven by lots of factors including how much lean muscle you have, your age etc - not just by the food or drink you’re being sold.

The Myths

Eating "Metabolism-boosting" foods and drinks

Green tea extract, cayenne pepper, ginger, coffee, and apple cider vinegar all appear in “metabolism-boosting” conversations. The evidence for most is underwhelming. Green tea, caffeine and capsaicin do produce a very small increase in your metabolism, but it is short-lived, and diminishes with continued use as the body develops tolerance.

Eating small meals frequently

The idea that eating small, frequent meals keeps metabolism elevated is one of the most persistent nutritional myths. Research has shown that total daily energy expenditure does not differ meaningfully between three and six meals when total caloric intake is matched.

Detoxes and juice cleanses

No credible evidence supports the use of detox programmes or juice cleanses for metabolic enhancement. The liver and kidneys are the body's detoxification systems, and they function independently of whatever cleanse is being marketed.

What Influences Metabolic Rate

Muscle mass

This is a factor you can control. Muscle tissue burns roughly 13kcal per kilogram per day at rest, compared to roughly 4.5kcal per kilogram for fat tissue. It is a modest difference, but consistent resistance training comes with a whole host of benefits than just the calorie math alone.

Protein intake

Protein has the highest thermic effect compared to carbohydrate and fat. Roughly 20-30% of its calories are burned off in processing (roughly 5-10% for carbs and 0-3% for fat). That means that a diet higher in protein therefore produces a small but genuine increase in daily energy expenditure.

Sleep

Skipping sleep doesn’t just make you tired. It can change what and how much you eat. Research found that partial sleep restriction led people to eat an average of 385 extra calories the next day. This isn’t necessarily about metabolism ‘slowing down’ - but more about appetite and food choices on too little sleep.

Not crash-dieting

This is counterintuitive but important. Very low calorie diets (obesity guidelines put the floor around approximately 1,200 calories for women and 1,500 for men) can trigger metabolic adaptation. This is where the body responds to perceived starvation by lowering RMR, increasing hunger hormones, and increased breakdown muscle for energy. This is reversible, but exactly why aggressive diets tend to fall short.

The Bottom Line

Most “metabolism boosters” are chasing effects that are real but small, temporary or simply non-existent. Two things that are worth your effort are building and keeping muscle, and steering clear of the kind of severe calorie restriction that pushes the body into adaptation mode. That being said, if you are experiencing unexplained problems related to your metabolism, it is best to speak to a medical professional for advice.

Words by Katherine Barrett, BSc Food Science and Nutrition, Huel nutrition team