The researchers reached this estimate by pooling data from 17 previously published studies that had evaluated the link between sugary drinks and diabetes risk.
And here's what upends conventional thinking: After the researchers adjusted their estimates for body weight, they found that — even for thin or normal-weight people — one sugary drink per day was associated with a 13 percent increased risk.
"So even if people are lean, if they continue consuming sugar-sweetened beverages, they have a greater likelihood of developing Type 2 diabetes," study author Fumiaki Imamura, of the University of Cambridge School of Clinical Medicine, told us.
The studies he looked at were observational, so they can't prove cause and effect. But the link between sugary drinks and diabetes is solid, since researchers say they understand the biological mechanisms of how too much sugar can overwork the endocrine system.
As we've reported, big soda companies including Coca-Cola and Pepsi have agreed to market more water and low-calorie beverages. And they've pledged to cut back on portions, too.
But it's not clear that making a switch to diet drinks leads to any advantage.
The new BMJ study also points toward an association between artificially sweetened drinks and a higher risk of diabetes, as well as fruit juices, but the evidence wasn't strong enough to make a solid conclusion. The authors say that these drinks "seemed not to be healthy options for the prevention of Type 2 diabetes."
This is not the first study to come to point to the "diet-soda paradox." As we've reported, the San Antonio Heart Study found a significant link between diet soda consumption and weight gain over time.
It's tricky to unravel. "People gaining excessive weight might switch to diet drinks and still get diabetes because of their other risk factors," explains David Ludwig, director of the New Balance Foundation Obesity Prevention Center at Boston Children's Hospital.
The researchers who published the paper estimate that, if Americans gave up their daily sugary drink habit, 2 million cases of diabetes could be prevented by 2020 — "so potentially, millions of cases of diabetes [prevented] as the result of this one behavior," Ludwig says.
It's something to consider the next time you feel thirsty.
The soda industry responded to the findings of the BMJ paper with a statement saying:
"The authors of this study acknowledge their findings do not show drinking beverages of any type causes chronic disease. Even so, our industry is committed to being part of real solutions to public health challenges."