We've all seen messages from the “food police” telling us that sugary snacks are bad. Ironically, these messages may backfire, causing us to eat more.

Researchers at Arizona State University, Nguyen Pham, Naomi Mandel, and Andrea Morales, have shown, in research published in the Journal of the Association for Consumer Research, that dieters ate 39 percent more sweet biscuits after seeing a “food police” style message that said, “All sugary snacks are bad” than those who saw a positive message.

The researchers conducted three studies to demonstrate that negative one-sided messages about food can lead to backfire effects. In the first study, 380 participants read a positive, negative, or neutral message about dessert. Dieters who saw the negative message had more positive thoughts about unhealthy foods, but non-dieters did not show any difference. Moreover, thoughts about healthy foods or non-food words were unaffected by the messages. “What these results show us,” Pham explains, “is that rather than leading dieters to make healthier choices, these food police messages are actually making unhealthy foods even more enticing to dieters.”

In the second study, 397 participants read a one-sided positive or negative about sugary snacks and then watched a short video while eating chocolate-chip cookies. Dieters who saw the negative message consumed 39% more cookies than dieters who saw the positive message. As in the first study, non-dieters were unaffected by the messages about food. The third study focused on snack choice and examined how reactions to two-sided messages, which contain both positive and negative information about food, might reduce the backfire effects. Among 324 participants, dieters who saw the negative message chose 30 percent more unhealthy snacks than dieters who saw the positive message, while dieters who saw the two-sided message chose 47 percent fewer unhealthy snacks than those who saw the negative message.

In an attempt to reverse the obesity epidemic and to try and provide useful information to consumers about the dangers of unhealthy eating, this research shows that there is a real danger in using messages that convey only negative information about food. Mandel warns, “Our work shows that negative messages about unhealthy food will backfire among dieters. If you want to change what they eat, a more even-handed message that contains both positive and negative information is the way to go.”