CHICAGO (AP) -- Would U.S. teens be any slimmer if Katy Perry hawked kale and quinoa?

New research doesn't prove a link, but its authors think music stars popular with teens may be contributing to the obesity epidemic by endorsing fatty fast food, snacks and soda.

The study shows that 20 of the hottest teen-music heartthrobs have done TV ads or other promotions for products nutritionists consider unhealthy.

Of 107 food and drink endorsements included in the study, few were for nutritious foods, the researchers said. Lead author Marie Bragg, a food policy and obesity researcher at New York University, singled out one "natural whole-food product." That was South Korean pop star Psy's "crackin' gangnam-style" TV ad for Wonderful pistachios, shown during the Super Bowl in 2013.

About 80 percent of celebrity-endorsed food ads were high-calorie products including snack chips and chocolate, or fast-food restaurants including McDonalds, Chili's and A&W. Most of the beverage ads were for sugary sodas.

The list includes Perry endorsements for Pepsi and Popchips; Justin Timberlake ads or promotions for Chili's, McDonald's and Pepsi; and will.i.am ads or campaigns linked with Coca-Cola, Doritos, Dr. Pepper and Pepsi.

The study was published Monday in the journal Pediatrics.

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Ads can influence behavior, and the researchers say the results have important implications, given the nation's high obesity rates. Government statistics show that about 20 percent of U.S. teens are obese and even more are overweight.

"Celebrities should leverage their influence to promote more healthful messages," the researchers said.

They selected music performers who have appeared on Teen Choice Award shows and who had hits on the Billboard Hot 100 Charts in 2013 and 2014. They included ads from 2000 to 2014.

They cited previous studies linking food and beverage marketing with excess eating and childhood obesity. Bragg noted a 2013 study from Australia that found sports celebrity endorsements influenced 11-year-old boys to buy fast food.

Bragg said it would be unrealistic to expect teens to only eat healthy foods, or to ask celebrities to only endorse those products. She said "moderation" and "a better balance" of ads would be ideal.