New research suggests a simple solution may help keep kids' portion sizes in check: smaller plates.

Grown-ups long long been told to downsize dishes to make smaller portions look like more food.

But Temple University associate public health professor Jennifer Orlet Fisher said conventional wisdom held that kids are better than adults at eating when they're hungry, and stopping when they're full. Her recent study challenges that notion.

"The results of this study suggest that aspects of kids' eating environments are influencing how much is enough when they're serving themselves in a way that has nothing to do with whether they are hungry or full," Orlet Fisher said.

Orlet Fisher gave first-graders in a private North Philly school dishes about the size of dinner plates or salad plates at different serve-yourself lunches.

She found kids with the bigger plates helped themselves to 90 calories more, and ate about half of those additional calories.

"I think that most of us are happy just to get food on the table, and we're not sitting down necessarily with measuring cups to figure out how much to serve kids," Orlet Fisher said. "This is something relatively straightforward and simple that parents can do without a lot of extra work that may help keep kids' portion sizes in check."

Orlet Fischer says the additional calories on the larger plates were more likely to be carbohydrates or protein. Kids rarely served themselves extra vegetables.