Nov. 9 (HealthDay News) -- School programs that promote healthy eating and exercise can help students lose weight, researchers say, but kids often pack on the pounds again during summer holiday.

The study was conducted by a team at the Agatston Research Foundation in Miami Beach, Fla. Their "Healthier Options for Public Schoolchildren" study included 3,200 children (48 percent Hispanic) from six elementary schools --- four schools tried out the intervention, while two did not and served as controls.

Programs at the four intervention schools included healthy food choices, nutrition/lifestyle education, school gardens, and other wellness projects.

Children at the control schools received traditional dietary and physical activity instruction.

By the second year, there were "significant differences" in body mass index (BMI) scores between students at the intervention schools and those at the control schools. However, during summer vacation, students at both the intervention and control schools showed increases in BMI, the researchers found.

The study was to be presented Wednesday at the American Heart Association annual meeting, in Orlando, Fla.

SOURCE: Nov. 7, 2007, presentation, American Heart Association annual meeting, Orlando, Fla.