The supplement aisle is full of products claiming to "boost your metabolism." But do any of them actually work — and if so, by how much? Here is what the research says, without the marketing spin.
Key takeaways
- Some supplements can modestly support metabolism — but none replace a healthy lifestyle.
- Green tea extract may increase 24-hour energy expenditure by roughly 4%, according to PubMed research.
- Caffeine can temporarily raise calorie burn, but the effect diminishes with regular use.
- L-carnitine, B vitamins, and iron are only effective when there is a proven deficiency.
- Capsaicin shows limited real-world impact at practical doses.
Do metabolism supplements work?
The short answer: some have a small, scientifically demonstrated effect. The longer answer: that effect is modest, often temporary, or only relevant when there is an underlying deficiency. No supplement comes close to the impact of building more muscle or exercising consistently.
For context, read our guide on what metabolism is and how it works before diving into what can influence it.
Green tea extract (EGCG + caffeine)
This is the best-researched supplement in the context of energy expenditure. Green tea contains catechins (particularly EGCG) and caffeine. Research published on PubMed found that a green tea extract rich in catechin polyphenols and caffeine increased 24-hour energy expenditure by an average of 4% compared to placebo.
One important caveat: Voedingscentrum notes that the overall evidence for health benefits of flavonoids (the category catechins belong to) is currently rated as insufficient. The effect exists, but it is small and diminishes with regular use.
In practice: green tea as a drink delivers less caffeine and catechins than concentrated supplements. Two to three cups per day is a reasonable habit; high-dose supplements have less research on long-term safety.
Caffeine (coffee, tea, supplements)
Caffeine stimulates the central nervous system and can temporarily increase energy expenditure. Coffee and tea are within standard dietary guidelines. Caffeine as a supplement is effective short-term, but your body adapts — with regular use, the metabolic effect diminishes.
In practice: up to 400 mg caffeine per day is considered safe for healthy adults (roughly four cups of coffee). Caffeine supplements add little beyond a normal coffee or tea habit.
Capsaicin (cayenne pepper, chilli)
Capsaicin — the compound that makes peppers hot — can mildly increase thermogenesis. The effect is small, and the amount consumed through food is usually insufficient to produce a measurable difference. High-dose supplements are difficult to sustain due to the intense heat sensation.
In practice: adding pepper and chilli to meals is harmless, but don't expect a meaningful impact on your weight.
L-carnitine
L-carnitine plays a role in transporting fatty acids to the mitochondria for burning. In theory this sounds useful — in practice, a healthy body produces enough L-carnitine on its own. Supplementation is mainly relevant for people with a deficiency (e.g., kidney disease or a strict vegan diet).
In practice: if you're healthy and eat a varied diet, additional L-carnitine is unlikely to provide a noticeable benefit.
B vitamins
B vitamins (B1, B2, B3, B5, B6, B7, B9, B12) play an essential role in energy metabolism — they are needed to convert carbohydrates, fats, and proteins into energy. But they only raise metabolism when there is a deficiency. If you eat a varied diet, supplementation is generally unnecessary.
In practice: B12 deficiency is more common in vegans and older adults. If you're in a risk group, a blood test is the right first step — not guesswork supplementation. Read more about the symptoms and effects of vitamin B12 deficiency.
Iron
Iron is needed to make haemoglobin, which transports oxygen to cells — including the energy-producing mitochondria. An iron deficiency can cause fatigue and impaired energy metabolism. Again: supplementation only helps when there is a confirmed deficiency.
In practice: if you experience persistent fatigue, get a blood test. Self-supplementing iron without a deficiency is unnecessary and can be harmful at high doses.
What actually works: the foundations
Supplements are additions, not replacements. The evidence-backed ways to support your metabolism consistently:
- Build muscle through strength training — this raises your BMR permanently
- Eat enough protein — protein has a higher thermic effect than other macronutrients
- Sleep well — sleep deprivation lowers energy expenditure
- Don't under-eat — extreme calorie restriction slows metabolism
Want to know exactly what you're eating? With Moveno, you photograph your meals and instantly see the nutritional breakdown — no manual input needed.
Track what you consume
To ensure you're getting enough nutrients, tracking your food helps. Our beginner's guide to calorie tracking gives you a practical starting point. Eating more protein also supports metabolism — read about high-protein foods for concrete examples.
The honest conclusion
Green tea extract and caffeine have the strongest evidence base for a small effect on energy expenditure. Other supplements help almost exclusively when there is a proven deficiency. No supplement brings you closer to your goals than consistent, healthy habits.
Read our related articles on slow metabolism and fast metabolism for broader context.
Sources
- PubMed — Efficacy of a green tea extract rich in catechin polyphenols and caffeine — study on the effect of green tea extract on 24-hour energy expenditure
- Voedingscentrum — Tea — information on catechins and health effects of green tea
- Voedingscentrum — Caffeine — safe caffeine consumption guidelines
- Voedingscentrum — Flavonoids — assessment of evidence for health effects of flavonoids
