From soda bans to gym class mandates, American schools are making healthier choices for their students.

Fewer U.S. schools offer students junk food or allow soda companies to advertise on campus, while more are improving the nutritional choices of the food they offer, according to an assessment by the U.S. Centers for Disease Control and Prevention (CDC).

The 2012 School Health Policies and Practices Study, the largest study of school health policies to date, shows improvements in U.S. school districts across several health measures, especially the food choices available to students.

“Schools play a critical role in the health and well-being of our youth,” said Thomas Frieden, CDC director, said in a statement. “Good news for students and parents—more students have access to healthy food, better physical fitness activities through initiatives such as ‘Let’s Move,’ and campuses that are completely tobacco free.”

The “Let’s Move!” campaign is First Lady Michelle Obama’s initiative to reduce childhood obesity rates.

Childhood obesity rates in the U.S. have doubled over the past 30 years to about 18 percent for children and adolescents. But the rate has recently decreased slightly in 19 states, the CDC reports.

The School Health Policies and Practices Study also found that:

  • 33.5 percent of schools allow soft drink companies to advertise on campus, down from 46.6 percent in 2006.
  • 43.4 percent of school districts prohibit junk food in vending machines, up from 29.8 percent in 2006.
  • 73.5 percent of schools address nutritional standards for foods sold outside of breakfast or lunch programs, up from 55.1 percent in 2006.
  • 52.7 percent of schools make school food nutritional information available to parents, up from 35.3 percent in 2000.
  • 93.6 percent of elementary schools require physical education classes, up from 82.6 percent in 2000.
  • 61.6 percent of school districts have agreements in place for shared use of parks and recreational activities by schools.
  • 67.5 percent of schools prohibit all tobacco use during any school activity, up from 46.7 percent in 2000.

These changes not only help to combat obesity, but also fight other health risks that can develop at a young age.

Research has shown that obese children are twice as likely to become obese adults. This can put them at a higher risk of developing chronic conditions, such as type 2 diabetes, heart disease, stroke, several types of cancer, and osteoarthritis, according to the CDC.

Besides physical health risks, studies have shown that obese children are more likely to be bullied, to have trouble in school, to have low self-esteem, and to report a lower quality of life.