Kids who drink whole milk tend to have a lower body mass index (BMI) score and higher vitamin D levels than those who drink any other kind of milk (or no milk at all), according to research published in The American Journal of Clinical Nutrition. And the difference is striking: Among the 2,745 kids who participated in the study, those who drank whole milk had a 0.72 lower zBMI score (a standardized children’s BMI score, adjusted to account for varying norms for kids’ ages) than children who drank 1 percent milk.

“That doesn’t sound like much, but it’s nearly the difference between being normal weight or overweight—or between being overweight and obese,” says lead researcher Jonathon Maguire, M.D., a pediatrician and researcher at St. Michael’s Hospital in Toronto. The hypothesis, Maguire says, is that whole milk is more satisfying, so kids who drink milk with less fat seek out calories elsewhere, often with less healthy foods.

As for the higher vitamin D levels, it’s surmised that because vitamin D is fat soluble, milk with more fat allows kids to absorb more. As Maguire puts it: “Vitamin D comes in on the coattails of fat.”