Drinking coffee could help keep you slim and ward off type 2 diabetes, study suggests

Drinking coffee regularly may reduce body fat and lower your risk of getting type 2 diabetes, a study suggests.

Researchers used genes which determine how fast people process caffeine to estimate the likely caffeine levels of almost 800,000 people over a lifetime, then looked at their weight.

People with the highest estimated caffeine level had a significantly lower body mass index (BMI).

They had a lower body fat percentage on average, and were also less likely to develop type 2 diabetes.

Coffee has long been suggested to burn fat and keep people slimmer, while previous studies have suggested people who drink three to five cups of coffee a day are less likely to get type 2 diabetes.

But the new study was needed because it was unclear if coffee-drinkers were benefiting from caffeine or avoiding type 2 diabetes for other reasons – for example, because they tend to be middle-class, so can afford a healthier lifestyle.

The latest research avoided this problem by looking specifically at people with genetic quirks affecting how the body processes caffeine.

The people who processed caffeine more slowly, just like regular coffee-drinkers, would typically have a high level of caffeine in their blood.

So when these people were found to have a lower BMI, body fat mass and type 2 diabetes risk, this provided more evidence that the caffeine was responsible.

Dr Dipender Gill, senior author of the study, from Imperial College London, said: ‘These results suggest caffeine may be linked to a lower body mass index, lower body fat and a reduced likelihood of developing type 2 diabetes.

‘It may improve people’s metabolism, although this doesn’t mean people should go out and drink lots of high-calorie caffeinated drinks like chai lattes.

‘If there is more evidence from larger trials in the future, it may suggest that people should consider drinking espressos or black coffee to reduce their risk of type 2 diabetes.’

The study, published in the journal BMJ Medicine, looked at people with variations in the CYP1A2 and AHR genes, which meant they broke down caffeine at different rates.

People who broke down caffeine more slowly, so were likely to have a higher level of it in their blood, had a lower risk of type 2 diabetes.

Analysis suggested about half of these people’s reduced risk of type 2 diabetes was explained by them having a lower body mass index.

Being thinner reduces the risk of developing the condition, which affects one in 10 people over the age of 40.

There is some evidence that caffeine causes the body to burn more of its fat stores, or simply makes people feel more full so that they eat less.

An average cup of coffee contains around 70 to 150 mg of caffeine, with evidence suggesting a daily intake of 100 mg may increase energy expenditure by around 100 calories a day.

However coffee also contains other compounds, like diterpenes, which may be less good for the metabolism.

The study found people with higher estimated levels of caffeine, based on their genes, were no less likely to develop major cardiovascular diseases, such as stroke and heart failure.