Caffeine reduces body weight in obese mice by suppressing the appetite and increasing energy expenditure, according to a report published in Nature Communications this week. The study identifies some of the neural circuitry involved in this effect, providing new insights into the mechanisms by which caffeine regulates metabolism.

The consumption of caffeine has been linked to a reduction in weight gain, but the processes that underlie this effect are mostly unknown. To try to understand more about this association, Guo Zhang and colleagues look at the activity of adenosine receptors - which are blocked by caffeine - in a region of the brain called the hypothalamus, the central regulator of energy balance in mammals. They observe aberrant signalling of adenosine receptors in the hypothalamus of obese mice, but show that administering caffeine led to reduced food intake and body weight, and increased energy expenditure. Caffeine seems to mediate this effect by acting on adenosine receptors and promoting the release of oxytocin, a known regulator of energy metabolism.

It should be noted that the doses of peripherally administered caffeine used were very high (60mg/kg, estimated to be equivalent to 24-36 cups of coffee in humans) which reduces the application of this potential obesity treatment. Caffeine has been deemed safe for consumption in doses of up to 400 mg per day for the general population.