Chronic dieters tend to consume more calories when foods and packages are smaller, according to a study in the Journal of Consumer Research. Researchers examined consumer behavior regarding "mini-packs," 100-calorie food packages that are marketed to help people control calorie intake.

"Interestingly, one group that over-consumes the mini-packs is chronic dieters—individuals constantly trying to manage their weight and food intake," write the authors.

The researchers believe their research shows that the ubiquitous small packages may actually undermine dieters' attempts to limit calories. "On the one hand, consumers perceive the mini-packs to be a generous portion of food (numerous small food morsels in each pack and multiple mini-packs in each box); on the other hand, consumers perceive the mini-packs to be diet food. For chronic dieters, this perceptual dilemma causes a tendency to overeat, due to their emotion-laden relationship with food."

In a series of studies, the researchers assessed peoples' perceptions of M&Ms in mini-packs versus regular-sized packages. They found that participants tended to have conflicting thoughts about the mini-packs: They thought of them as "diet food," yet they overestimated how many calories the packages contained. In subsequent studies, the researchers assessed participants' relationship with food, dividing them into "restrained" and "unrestrained" eaters. The "restrained" eaters tended to consume more calories from mini-packs than "unrestrained" participants.

The authors conclude that dieters should keep an eye on small packages: "While restrained eaters may be attracted to smaller foods in smaller packages initially, presumably because these products are thought to help consumers with their diets, our research shows that restrained eaters actually tend to consume more of these foods than they would of regular foods."