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When Michelle Obama encourages Americans to eat more fruits and vegetables through her Let's Move! campaign, the message is well-received. But a new study says that negative ads, like these by Children's Healthcare in Atlanta, which suggest that being fat takes the fun out of being in kid, don't work as well.

When Yale researcher Rebecca Puhl organized an online experimental study with 1,041 Americans to determine the effects of 30 public service announcements from various countries, she found that negative messages could have the opposite effect on overweight Americans.

“By stigmatizing obesity or individuals struggling with their weight, campaigns can alienate the audience they intend to motivate and hinder the behaviors they intend to encourage,” she said in a press release. “Public health campaigns that are designed to address obesity should carefully consider the kinds of messages that are disseminated, so that those who are struggling with obesity can be supported in their efforts to become healthier, rather than shamed and stigmatized.”

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Campaigns that didn't mention obesity at all, but which offered specific tips to change behavior, were rated the most motivating. Campaigns that used shame or blame, like the Atlanta ad above, were rated least motivating. The study was published online this week in the International Journal of Obesity.

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Nina Savelle-Rocklin, a psychotherapist who specializes in eating disorders, is not in the least surprised by the results of the study, she told the Los Angeles Times: "Shame is about feeling bad about who you are," she told the newspaper. Many who struggle with weight "are going to turn to food... . It's just a recipe for disaster."