Teenagers' natural desire to rebel against authority could be tapped to drive them to replace junk food with healthier choices, a study has found.
Food marketing, designed to foster strong positive associations with junk food in kids' minds and to drive overeating, is one of the biggest obstacles in the public fight against obesity.
The study, published in the journal Nature Human Behaviour, found that a simple and brief intervention can provide lasting protection for adolescents against these harmful effects of food marketing.
The method works in part by tapping into teens' natural desire to rebel against authority, researchers said.
The team from the University of Chicago in the US went into classrooms and had one group of students read a fact-based, expose-style article on big food companies.
The article framed the corporations as manipulative marketers trying to hook consumers on addictive junk food for financial gain.
The stories also described deceptive product labels and advertising practices that target vulnerable populations, including very young children and the poor.
A separate, control group of students received traditional material from existing health education programs about the benefits of healthy eating. The researchers found that the group that read the exposes chose fewer junk food snacks and selected water over sugary sodas the next day.
Teens first read the marketing expose material, and then did an activity called "Make It True," meant to reinforce the negative portrayal of food marketing.
The students received images of food advertisements on iPads with instructions to write or draw on the ads - graffiti style - to transform the ads from false to true.
The study found that the effects of the marketing expose intervention endured for the remainder of the school year - a full three months.
The effects were particularly impressive among boys, who reduced their daily purchases of unhealthy drinks and snacks in the school cafeteria by 31 percent in that time period, compared with the control group.
Researchers found that reframing how students view food-marketing campaigns can spur adolescents, particularly boys, to make healthier daily dietary choices for an extended period of time.
Food marketing is deliberately designed to create positive emotional associations with junk food, to connect it with feelings of happiness and fun.Christopher J Bryan, from University of Chicago
The intervention produced an enduring change in both boys' and girls' immediate, gut-level, emotional reactions to junk food marketing messages.
Teenage boys, a notoriously difficult group to convince when it comes to giving up junk food, started making healthier food and drink choices in their school cafeteria.
"One of the most exciting things is that we got kids to have a more negative immediate gut reaction to junk food and junk food marketing, and a more positive immediate gut reaction to healthy foods," said Bryan.
This relatively simple intervention could be an early sign of a public-health game changer, researchers said.