More United States students have access to healthier food, better physical fitness programs and more schools are smoke free, federal health officials announced, according to ABC News.

A government survey found 44 percent of school districts banned junk food from vending machines last year. This is up from 30 percent in 2006. The survey also found a drop in numbers of the districts that took a cut in soft drink sales, received donations from soda companies, or allowed soda company advertising.

According to ABC News, it's not clear on whether the new changes are actually making an impact. The overall proportion of American children who are overweight or obese has been holding steady at around 17 percent, according to government statistics.

"There are lots and lots of factors that go into obesity rates," said Nancy Brener, lead author of the government report on the study. Brener is a health scientist at the Centers for Disease Control and Prevention.

It's believed that diet and exercise at home are at least as important as what kids are exposed to on school grounds. The survey studied more than 800 U.S. school districts, last year. The Center for Disease Control and Prevention does the study every six years.

According to the CDC, the percentage of school districts that received soft drink sales fell from 82 percent in 2006 to 69 percent in 2012. 

The percentage of soft drink companies allowed to advertise soft drinks on school grounds dropped from 46.6 percent to 33.5 percent. The percentage of districts that required schools to prohibit offering junk food in vending machines increased from 29.8 percent to 43.4 percent.

The study also found:

* The amount that received cash awards, equipment donations or other soda companies fell from 52 percent to 34 percent.

* Food contracts for school breakfast or lunch increased from 55.1 percent to 73.5 percent.

* In 2000, 82.6 percent of school districts required elementary schools to teach physical education, but that rose to 93.6 percent in 2012.

According to the United Press International, Dr. Tom Frieden said the report used data from the 2012 School Health Policies and Practices Study is the largest and most comprehensive survey to assess school health policies.

"Schools play a critical role in the health and well-being of our youth," Frieden said in a statement, according to UPI. "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."'