Consuming caffeine can lead to weight loss, and now scientists have discovered why that is. Their research could pave the way for the development of new obesity treatments in the future.

Two billion people globally are now considered overweight or obese, according to recent estimates. This means that a quarter of the world population is at risk of developing devastating health conditions ranging from diabetes to cardiovascular issues and cancer.

Currently, medical interventions for obesity include pharmacological and surgical treatment, but only three drugs have been approved by the US Food and Drugs Administration (FDA) for the long-term management of obesity.

In recent years, studies have established a link between caffeine consumption and weight loss. Obesity researchers have been keen to investigate it further, but they had so far been unable to identify the underlying mechanisms.

In a study now published in the journal Nature Communications, scientists studied the activity of the adenosine receptors in the brain – receptors that are well known to be blocked by caffeine.

They worked with mice, monitoring the activity of adenosine receptors known as A1R in a brain region called the hypothalamus, which regulates energy balance in mammals. They injected high doses of caffeine directly in the brain of the animals.

"Our hypothesis was that caffeine might regulate energy balance by acting on the hypothalamus, a tiny but important structure in the central nervous system. The hypothalamus has long been known as the centre controlling mammal's energy balance. In this study, we employed several approaches, monitoring food intake and body weight, measurement of energy expenditure and the temperature of the skin," lead author Guo Zhang, from Huazhong University of Science and Technology (China), told IBTimes UK.

With his team, he observed unusual brain activity in obese mice, with abnormal signalling of the adenosine receptors in the hypothalamus. After scientists administered the caffeine in their brains, this changed, and the animals' food intake was reduced and body weight decreased.

They also observed an increase in the mice's energy expenditure – the amount of calories burnt by the animals. "The results clearly show that both the peripheral and central treatment of caffeine could reduce obesity animal's body weight and appetite, while promoting the generation of heat," Zhang added.

The study thus suggests that caffeine intake and weight loss are linked, because caffeine suppresses appetite and increases energy expenditure.

Obesity treatment

There is still a way to go before these findings can be relevant to the treatment of obesity. At any rates, the method would have to be adapted to do the same study in humans, as the high doses given to the mice are indeed estimated to be the equivalent of 24 to 36 coffee cups in humans.

Scientists say that in the future, one approach could be to develop drugs targeting the adenosine receptors A1R in the brain.

"We hope that our study and future research into caffeine can help combat of obesity. However, we believe that it might be better to use our research to find more potent and specific agents targeting A1R. More research is needed to achieve this" Zhang said.

Sugar Tax
The findings do not suggest you should drink high doses of coffee to lose weight. Christopher Jue/Getty images

But whether these findings give way to a new generation of obesity medication or not, they are still valuable as they uncover previously unknown biological mechanisms and answer important basic science questions.

Gareth A Wallis, a senior lecturer in Exercise Metabolism & Nutrition at the University of Birmingham who was not involved with the study, told IBTimes UK: "The findings are interesting as they provide a proof-of-concept that caffeine is capable of regulating the hypothalamic A1R pathway and energy balance. But the observations are in mice, so they should be interpreted with caution before confirming that the same pathway is critically important in humans, and importantly whether the type of caffeine dose that can be consumed safely by humans can yield the benefits observed in these mice through the mechanisms proposed by the authors."