Regulating fast food kids' meals that include toys may end up making the meals healthier, according to a new study.

If a proposed new policy in New York City is approved, then fast food meals that come with toys would contain fewer calories overall, and fewer from fat and sodium, researchers report.

"We can create policies that will nudge us toward healthier behaviors," said senior author Marie Bragg, of NYU Langone Medical Center in New York.

The proposed policy, which was introduced to the New York City Council, says fast food meals that come with a small toy must include a serving of fruit, vegetable or whole grain. The law would also limit meals with toys to no more than 500 calories, and it would place additional restrictions on fat and salt.

To estimate the effect of the proposal, researchers analyzed food purchases made by 358 adults for 422 children at Burger King, McDonald's and Wendy's restaurants in New York City and New Jersey in 2013 and 2014.

The average child in the study was seven years old.

As reported in the American Journal of Preventive Medicine, the adults purchased an average of 600 calories of food for each child, with a third of those calories coming from fat.

The meals contained an average of 869 mg of salt - more than half the total daily limit recommended by the American Heart Association.

About 35 percent of the children ate kids' meals that came with toys - and 98 percent of those meals did not meet the proposed guidelines, the researchers write.

If all the meals with toys met the proposed standards, children would consume 9 percent fewer calories and there would also be 10 percent reductions in salt and calories from fat, the researchers calculated.

"It’s a rather small amount in comparison to how bad the country's obesity problem really is," Bragg acknowledged. But small changes could add up, she said.

"There's a lot of value in the incremental changes that can sum up to a great impact with all the other changes occurring in the environment," such as policies that create healthier workplaces and communities, Bragg told Reuters Health.

Bragg hopes fast food restaurants won't try to sidestep any new policies.

"We’re at a point where we have to move the needle and we have to do it with policies like this," she said.