CHICAGO — Head Start programs have been shown to help poor children do better in school, but they may also help them fight obesity, a study suggests.

During a year of Head Start preschool, obese and overweight children were much more likely to slim down than comparison groups of kids.

The study involved almost 44,000 preschool-aged children in Michigan and the researchers, from the University of Michigan, acknowledge it has weaknesses. But they say the potential benefits are important because obesity is so hard to treat and affects low-income children disproportionately.