A new study has found that the rate at which we metabolise caffeine may have an impact on our weight, though further research will be needed to work out whether drinking more coffee is actually beneficial.
Dr Dipender Gill, a clinical scientist at Imperial College London, was part of the team of researchers who worked on the study.
He said this new research looked into the impact of genetics, making the findings more robust than those previously undertaken.
Prior studies were unable to show a causal effect between caffeine and weight – Dr Gill hopes that these new findings will be used “to direct further research including potential clinical studies”.
Talking to the PA news agency he said, “95% of your caffeine is metabolised by an enzyme” and two genes called CYP1A2 and AHR affect the function and level of that enzyme.
By looking at these genetic variants that cause people to metabolise caffeine faster or slower, the study found that slower metabolisers have higher plasma caffeine levels and go on to have a lower body mass index and a lower risk of diabetes.
“It’s the plasma caffeine that’s doing that,” he said.
Dr Gill said that on a population level, this means that people who metabolise caffeine more slowly are 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.”
It’s hoped the present study will direct further research, including on whether drinking more coffee can help people stay slim.
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However, he made it clear that people should not be changing their habits for now.
“Certainly people shouldn’t start drinking more coffee or tea to try and lose weight, and that’s also because coffee and tea and caffeine can have adverse effects as well.
“So 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 is currently unclear what proportion of the population metabolises caffeine more quickly.
The study included almost 10,000 people who were taking part in six longer-term studies.
The new research was published in the journal BMJ Medicine.
