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Health: How caffeine helps mice to lose weight
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.
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Dr Ben Desbrow is an Associate Professor in Sports Nutrition at the Menzies Health Institute Queensland at Griffith University
This is largely a mechanistic study (on rats) attempting to better understand why humans who regularly consume caffeine find it easier to regulate their body weight.
It appears that when fed a high-fat diet, changes occurred to specific areas of the animal's hypothalamus (the central regulator of energy balance) to increase both the circulating levels of adenosine and a specific adenosine receptor (A1R) which resulted in rotund rodents.
Caffeine is a well-known adenosine receptor antagonist. In this study, it was demonstrated that caffeine assists in blocking the downstream effects of excessive adenosine (i.e. usually increased voluntary energy consumption and reduced physical activity).
The major limitation with the application of the study (apart from it employing rats) is the dose of caffeine provided, which was 60mg/kg body weight. This is a huge dose, with an equivalent dose in humans likely to lead to severe caffeine toxicity (if not a fatal cardiac event). In the rats the high dose of caffeine resulted in greater voluntary physical activity and a reduced food intake.
We've performed a similar study using caffeine to manipulate responses to diet and exercise in humans (albeit with a much lower caffeine dose (6mg/kg body weight)). In this study we also found that short-term food consumption was reduced and, importantly, that participants found undertaking exercise more enjoyable.
Professor Linda Tapsell is Professor of Nutrition and Dietetics at the University of Wollongong
This is an interesting study exposing pathways of action of caffeine, a chemical compound delivered in substantial amounts by coffee. To do this, the study was highly controlled and conducted in mice, and the dose was very high. The research adds a small component to knowledge on dietary management of body weight.
It creates the hypothesis that coffee may earn a position on the ‘weight loss foods team’. There are other dietary components that will also contribute in other ways.
Coffee is basically a seed, consumed largely as a beverage. It can be part of the Mediterranean-style dietary pattern which delivers compounds that have a beneficial influence on a number of metabolic pathways.
This research adds support to plant based dietary patterns containing foods such as seeds, wholegrains, nuts, vegetables, fruits, in line with national dietary guidelines
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