Blood caffeine levels clue to staying slim and less diabetes risk

Ability to metabolise caffeine more slowly seen to affect BMI and chances of diabetes

Don't change your caffeine habits yet, doctor warns, as more research is needed. Getty
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Higher blood caffeine levels may reduce the risk of diabetes and could help people to stay slim, researchers said on Tuesday.

But they also warned people not to change their coffee drinking habits just yet.

The rate at which people metabolise caffeine may have an effect on their weight and play a role in their diabetes risks, research published in the journal BMJ Medicine says.

Dr Dipender Gill, a clinical scientist at Imperial College London who worked on the study, said earlier research had not been able to show a causal effect between caffeine and weight, but the new study looked at genetics, making the findings stronger.

Dr Gill said that “95 per cent of your caffeine is metabolised by an enzyme” and that two genes — CYP1A2 and AHR — affect the function and level of that enzyme.

“We found that slower metabolisers have higher plasma caffeine levels, and those with higher plasma caffeine levels go on to have a lower body mass index and a lower risk of diabetes,” he said.

“It’s the plasma caffeine that’s doing that.”

Dr Gill said that also meant people who metabolised caffeine more slowly were more likely to be thinner and have less risk of diabetes.

“If you’re a faster metaboliser, you have lower plasma caffeine levels and you are, on average at a population level, at slightly higher risk of diabetes and have a slightly higher body mass index,” he said.

Dr Gill said the study could inform more research, including on whether drinking more coffee could help people to stay slim.

“Certainly people shouldn’t start drinking more coffee or tea to try to lose weight, and that’s also because coffee and tea and caffeine can have adverse effects as well,” he said.

“Some people might find it difficult to sleep and some people can get palpitations, so I think, based on this study, people should not change their lifestyle or behaviour.

"But our findings should be used to direct further research, including potential clinical studies.”

Dr Gill said it was so far unclear as to what proportion of the population metabolised caffeine more quickly.

The study included almost 10,000 people who were taking part in six longer-term studies.

For now, further research will be needed to work out whether drinking more coffee is beneficial.

Updated: March 14, 2023, 10:30 PM