In a research paper published Tuesday in the scientific journal BMJ Medicine, health experts from Sweden, Denmark, and the U.K. outlined the outcome of their analysis on how caffeine intake affected body weight, cardiovascular health, and diabetes risk.

The research team used Mendelian randomization—a method of establishing cause and effect by looking at genetic evidence—to calculate predicted caffeine levels in the blood of around 10,000 participants and work out whether it was linked to BMI, body fat, and type 2 diabetes.

They found that high concentrations of caffeine in the blood was associated with a lower body mass index (BMI), the measure used to calculate whether someone is of a healthy weight, and lower body fat levels in general.

Caffeine has previously been associated with improving metabolism and burning fat.

Higher caffeine levels were also linked to a lower risk of type 2 diabetes, the study found. The study’s authors noted that almost half of the lower diabetes risk was derived from the apparent caffeine-induced reduction in BMI.

People who are overweight and have a high BMI are at greater risk of developing type 2 diabetes.

No strong association was found in the study between caffeine intake and risk of heart disease, heart failure, or stroke.

The study’s authors said their paper built on existing studies, one of which found an association between drinking between three and five cups of caffeinated coffee a day and a reduced risk of developing type 2 diabetes and cardiovascular disease, with each cup appearing to cut the diabetes risk by 7%. However, they noted that the nature of these observational studies meant—unlike research using their Mendelian technique—they could not reliably conclude that caffeine was the cause for the reduced health risks.

While the study’s authors said they had found “found evidence to support causal associations of higher plasma caffeine concentrations with lower [obesity levels] and risk of type 2 diabetes,” they said more trials were needed to assess whether calorie-free caffeinated drinks could play a role in reducing the risk of developing either.

The study was limited by the fact that the participants were mostly of European descent. African American, Hispanic, and Latino people and some Pacific Islanders are at higher risk of developing type 2 diabetes.

Earlier research

Previous studies on the health implications of caffeine consumption have produced mixed results.

In 2018, Swedish scientists found that drinking coffee lowered the risk of developing type 2 diabetes, while a study published last year showed that drinking up to three cups of coffee a day had a protective effect on heart health.

However, research published in 2020 found that substances found in unfiltered coffee can increase “bad” cholesterol, while links have also been drawn between caffeine intake and anxiety and sleep disorders.