Sugar is the reason of unhealthy treats, not fat, a new study says. Researchers monitored the brain activity of more than 100 teens as they drank chocolate-flavored milkshakes that had the same number of calories but were either high in sugar and low in fat, or the other way around, Newsmax Health reports.

Both types of shakes activated pleasure centers in the brain, but those that were high in sugar did so far more effectively.

"We do a lot of work on the prevention of obesity, and what is really clear not only from this study but from the broader literature over all is that the more sugar you eat, the more you want to consume it," study lead author Eric Stice, a senior research scientist at the Oregon Research Institute, told The Times.