Do you just loathe your friend who can open a bag of chips and eat just a few when you can't stop eating until the bag is empty? Why is it some people seem to have more self control than others? That is what researchers at the University of Minnesota (UMN) set out to answer, and they found that people can learn to stop eating unhealthy food sooner.

Researchers conducted a set of experiments using undergraduate students, starting with a questionnaire routinely used to determine people's levels of self-control.

The first experiment consisted of 199 undergraduates choosing between peanuts and raisins (healthy snacks) or M&M's and Skittles (unhealthy snacks) to eat while watching a short video. The students with high self-control, as determined by the questionnaire, quit eating the unhealthy foods faster than they did the healthy foods. Whether the snack was healthy or unhealthy didn't make a difference to how fast or slow people with low self-control quit eating.

Those with low self-control ate less when they had to pay attention to how much they were eating.

In the second experiment, Joseph Redden, assistant professor marketing at UMN's Carlson School of Management and Kelly Haws, assistant professor of marketing at Texas A&M University and co-author of the study, aimed to rule out a physiological explanation for the findings of the first experiment. One hundred fifty-four students were asked to rank their level of enjoyment and satiation (feeling of fullness) while eating a bowl of graham crackers, either described as healthy or not healthy. Once again, those with high levels of self-control lost their desire to eat the graham crackers labeled "unhealthy" faster than the "healthy" ones. And they lost that desire faster than those with low self-control.

Could it be that the people with higher levels of self-control were paying more attention to how much they were eating? Redden and Haws tested this theory by making people pay attention to what they ate. They had 465 undergraduates count the number of times they swallowed either a healthy or unhealthy snack using a clicker like those used to count pitches in baseball. In this experiment, those with low self-control looked a lot more like the people with high self-control. In other words, those with low self-control ate less when they had to pay attention to how much they were eating.

Finally, in a fourth experiment, the researchers gave 228 undergraduate students access to full portions of the snack of their choice for 20 minutes while they performed unrelated tasks. Then the snacks were removed and the students were asked questions about their eating of the food. The results confirmed the findings of the previous experiments, particularly the finding that how fast people stop eating depends on how much attention they are paying to what they are eating.

"When people talk about self-control, they really imply that self-control is willpower and that some people have it and others don't when facing a tempting treat," said Redden. "In reality, nearly everyone likes these treats. Some people just stop enjoying them faster and for them it's easier to say no."

The results of this study could be encouraging news for those who struggle with their weight. Monitoring how much a person eats may enable self-control, and if people realize that they can learn to eat less unhealthy food simply by monitoring their intake, it could help in the fight against obesity.

"People can essentially use attention for how much they are consuming instead of relying on self-control," said Redden. "Really paying a lot more attention to the quantity will lead people to feel satiated faster and eat less."

The study was published online ahead of print in the Journal of Consumer Research.