New research powerfully strengthens the case against soda and other sugary drinks as culprits in the obesity epidemic.
A huge, decades-long study involving more than 33,000 Americans has yielded the first clear proof that drinking sugary beverages interacts with genes that affect weight, amplifying a person's risk of obesity beyond what it would be from heredity alone.
This means that such drinks are especially harmful to people with genes that predispose them to weight gain. And most of us have at least some of these genes.
In addition, two other major experiments have found that giving children and teens calorie-free alternatives to the sugary drinks they usually consume leads to less weight gain.
Collectively, the results strongly suggest that sugary drinks cause people to pack on the pounds, independent of other unhealthy behavior such as overeating and getting too little exercise, scientists say.
That adds weight to the push for taxes, portion limits like the one just adopted in New York City, and other policies to curb consumption of soda, juice drinks and sports beverages sweetened with sugar.
Soda lovers do get some good news: Sugar-free drinks did not raise the risk of obesity in these studies.
"You may be able to fool the taste" and satisfy a sweet tooth without paying a price in weight, said an obesity researcher with no role in the studies, Rudy Leibel of Columbia University.
The studies were being presented Friday at an obesity conference in San Antonio and were published online by the New England Journal of Medicine.
The gene research in particular fills a major gap in what we know about obesity. It shows how behavior combines with heredity to affect how fat we become.