Fat burners

What it is

"Fat burners" or thermogenics are stimulant-based blends sold to boost metabolism and strip fat. In practice they are mostly caffeine wrapped in marketing — and no supplement overrides the need for an energy deficit.

What the evidence shows

Burning fat. Marketing claim· human data Most of any real effect is the caffeine — a mild, temporary bump in metabolic rate and appetite suppression. The other ingredients are typically underdosed or unproven, and none replace an overall energy deficit.

Who it suits

There is little case for them. What actually drives fat loss is a sustained energy deficit, enough protein, resistance training to keep muscle, and daily movement — none of which a pill can substitute for.

Practical notes

The category has a chequered safety record: high stimulant loads, hidden doses, and historically banned or withdrawn ingredients. Stacking a fat burner with coffee or a pre-workout risks jitters, a racing heart and poor sleep. If you use caffeine as a tool, our caffeine calculator helps you manage the total. People who are pregnant or have heart, blood-pressure or anxiety conditions should avoid them.

Sources

PubMed: thermogenic 'fat burner' supplements — efficacy, ingredients and safety (reviews and analyses)

Frequently asked questions

Do fat burners work?

Most of any real effect is the caffeine — a mild, temporary bump in metabolic rate and appetite suppression. The other ingredients are typically underdosed or unproven, and none override the need for an overall energy deficit to lose fat.

What actually drives fat loss?

A sustained energy deficit, enough protein, resistance training to keep muscle, and daily movement. A 'fat burner' can't substitute for those; at best it's a small, stimulant-driven nudge.

Are they safe?

The category has a chequered safety record — high stimulant loads, hidden doses and, historically, banned or harmful ingredients. The risk-to-benefit balance is poor, especially alongside other caffeine sources.