Amid fervid criticism that New York City risks becoming a nanny state, city health officials this month banned the sale of supersize sugar-laden drinks in restaurants and movie theaters. Now scientists have handed the ban’s advocates a potent weapon: strong evidence that replacing sugared drinks with sugar-free substitutes or water really can slow weight gain in children.

Two-thirds of all American adults and one-third of children in the United States are overweight or obese. The contribution of sugary sodas and fruit drinks to this epidemic has been hotly disputed. But two new randomized clinical trials published on Friday in The New England Journal of Medicine lend credence to the idea that limiting access to these beverages may help reduce obesity.

Beverage industry officials denounced the research, which may fuel wider efforts to curb consumption through taxes or other restrictions.

In one of the new trials, researchers at Boston Children’s Hospital randomly assigned 224 overweight or obese teenagers to receive home deliveries of bottled water and diet drinks for one year. The children also were regularly encouraged to avoid sugary drinks. Those who received the shipments gained only 3.5 pounds on average during that year, while a comparison group of similar teenagers gained 7.7 pounds. The differences between the groups evaporated after the deliveries stopped.