She said any caffeinated drinks containing sugar and fat would offset the positive effects. The researchers said their work built on previously published research, which suggested that drinking three to five daily cups of coffee, containing an average 70-150mg of caffeine, was associated with a lower risk of type 2 diabetes and cardiovascular disease. As those were observational studies, they made it difficult to pinpoint whether the effects were because of caffeine or other compounds, the researchers said. This latest study used a technique known as Mendelian randomisation, which establishes cause and effect through genetic evidence. The team found two common gene variants associated with the speed of caffeine metabolism, and used these to work out genetically predicted blood caffeine levels and whether this was associated with lower BMI and body fat.
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