Especially when you're on a diet. 

By Grace Elkus
Updated January 26, 2016
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We know, we know—soda, sweets, and packaged snacks are bad for us. But despite the constant stream of messages that warn us of their health risks, why is it that we find ourselves reaching for sugar-laden foods?

Turns out, these “food police”-style messages might actually make dieters more inclined to eat sugary foods, according to a new study conducted by Arizona State University. The results are published in the Journal of the Association for Consumer Research.

To test the effect of these negative food messages, the researchers conducted three experiments. In the first, 380 dieting and non-dieting participants read either a positive, negative, or neutral message about dessert. Though the non-dieters' thoughts remained consistent throughout the messages, dieters who saw the negative message had more positive thoughts about unhealthy foods.

“What these results show is that rather than leading dieters to make healthier choices, these food police messages are actually making unhealthy foods even more enticing to dieters,” Nguyen Phang, one of the study's researchers, said in a statement.

In the second experiment, 397 participants read a one-sided message—either positive or negative—about sugary snacks, and then watched a short video while eating chocolate chip cookies. While non-dieters were again unaffected by the messages, the dieters who saw a negative message consumed 39 percent more cookies than the dieters who saw the positive message.

In the third and final experiment, 324 participants saw either a negative message, a positive message, or a two-sided message that included both positive and negative points. Once again, the dieters who saw a negative message chose more unhealthy snacks—specifically 30 percent more than the dieters who saw a positive message. Perhaps most significant, however, is that the dieters who saw the two-sided message chose 47 percent fewer unhealthy snacks than the dieters who saw the negative message.

“Our work shows that negative messages about unhealthy food will backfire among dieters," Naomi Mandel, another of the study's researchers, said. 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.”

Need help choosing a healthier snack? Check out these habits of highly successful snackers, and then get inspired by these nutritionist-approved picks.