“These results show that sugary beverages can have an effect on body weight quick quickly,” says Ludwig, “perhaps more so than any other single food product. We know of no other study where you eliminated one specific category of food and then show a changed body weight at one year.”

The trend did not persist, however, when the home deliveries ceased. The researchers continued to observe the teens for additional year during which time none received deliveries of no-calorie drinks. Not surprisingly, these teens began to drink more sugar-sweetened beverages and their weight started to creep back up.

That suggests that changing children’s eating and drinking habits isn’t simply a matter of educating them about nutrition and healthy foods. It also requires changing their environment, so that healthier alternatives become both accessible and convenient. “Children and adolescents will readily change their beverage habits if other products are available,” says Ludwig. “As long as we maintain environments of sugar-sweetened beverages where they are ubiquitous, and heavily marketed, it shouldn’t surprise us that they are drinking a lot of them. But if we create an environment that makes alternatives easy and convenient, they will drink those instead.”