Many states have already enacted their own laws mandating healthier non-cafeteria food options.
Jessica Donze Black, a dietician who leads the Kids' Safe and Healthful Foods Project, said the results show growing support for updating standards that surfaced in 1979.
"What has changed in the last 30 years is that the childhood obesity epidemic has more than tripled," she said. "The school environment has also changed. ... Today, there are a lot of other places throughout the day that compete with kids eating a healthy school meal."
Eighty percent of the 1,010 adults polled said they would support nutritional standards limiting the calories, fat and sodium in such foods. Seventeen percent would oppose it.
Most also agreed there are now few healthy options. Just 5 percent of adults said vending machines offered totally or mostly healthy choices compared with 10 percent for school stores and 21 percent for a la carte lunch lines.
Changes to school foods may be controversial. New standards for more fruits, vegetables and whole grains in traditional school meals announced in January drew scrutiny when lawmakers blocked limits to french fries and counted pizza as a vegetable because it contains tomato sauce.
Efforts to give students more healthy options to help fight childhood obesity have historically faced pressure from food and beverage companies and even from schools themselves, who rely on such food sales for extra cash.
But health experts, pediatricians and other advocates say that is changing as more companies and school districts come on board at a time when more than one-third of USchildren are overweight or obese.