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Walk five miles or drink a soda: Study looks at how messaging impacts teens’ choices


Signs telling teens they’d have to walk five miles to burn off the calories in a 20-ounce soda made teenagers more likely to buy smaller or healthier drinks, a study from the John Hopkins Bloomberg School of Public Health has found.

Calorie counts have been listed on food products for a long time, and thanks to the Affordable Care Act, chain restaurants with more than 20 locations will have to list calorie figures on menus starting next year. But the study’s authors argue numbers alone don’t give Americans enough information about what consuming calories means for them, which is why they wanted to study whether presenting calorie information in a different way could influence people to make healthier choices, according to a press release.

“People don’t really understand what it means to say a typical soda has 250 calories,” lead researcher Sara Bleich, an associate professor in the Department of Health Policy and Management at the Bloomberg School, said in the release. “If you’re going to give people calorie information, there’s probably a better way to do it. What our research found is that when you explain calories in an easily understandable way such as how many miles of walking needed to burn them off, you can encourage behavior change.”

How the study worked

Researchers picked six corner stores in low-income, predominately black neighborhoods in Baltimore. They posted brightly colored, 8 ½-by-11-inch signs featuring facts about the calories in 20-ounce bottles of soda, sports drink or fruit juice in the stores for six-week stretches between August 2012 and June 2013. The signs said one of four things:

  • Each bottle contained 250 calories
  • A bottle contained 16 teaspoons of sugar
  • It would take 50 minutes of running to work off the calories in a bottle
  • It would take 5 miles of walking to burn off those calories

The researchers observed 3,098 drink purchases made by customers between the ages of 12 and 18. They interviewed a quarter of those customers after they left the store. They found:

  • 35 percent of kids saw the signs
  • 59 percent of the teens who saw the signs believed them
  • 40 percent said they changed their behavior because of the signs

Bleich said the sign that discussed walking five miles was the most effective. Fifty-four percent of teens bought sugary drinks larger than 16 ounces before the sign was posted, while 37 percent sprung for larger drinks after the sign went up. Water purchases increased from 1 percent to 4 percent.

Certain neighborhoods picked for a reason

The researchers deliberately picked low-income, predominately black neighborhoods for the experiment because black adolescents are at high risk for obesity, Bleich said in the press release.

According to the Centers for Disease Control, obesity rates for black youth were 20.2 percent in 2011 and 2012. The rate for Hispanic children was slightly higher at 22.4 percent, while white youth had a 14.1 percent obesity rate and Asian kids had a 8.6 percent obesity rate.

Income also plays a role — the CDC has found that obesity rates tend to rise as income levels decrease.

Bleich told NPR that before the study, she wondered how concerned teens would be about something like the calories in a soda when they lived in neighborhoods where low incomes and high levels of drug use were a constant reality. Finding out the signs made a difference encouraged her.

“To me, the message is: Among a population for whom health is probably not a primary concern, we’re [seeing] a significant effect,” Bleich told NPR, adding that she thinks doing the same study in a higher-income neighborhood would show more drastic results.

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