A new study from the University of Southern California suggests that when it comes to fighting belly fat, upping one’s fiber intake might just be the key. The belly is a particularly undesirable area to pack on pounds, not for aesthetic reasons, but because it has been shown to signal an increased risk for developing heart disease and diabetes.

In those whose fiber intake increased over the two years, their belly fat decreased by about 4%. But in people whose fiber intake fell, their belly fat increased by a much larger amount, 21%.

The research team led by Jaimie N. Davis followed 85 overweight Latino participants aged 11−17 for two years, noting their fiber intake at the beginning and end of this time period. Davis notes that diets sometimes worsen during this period of life, so it is not surprising that fiber intake changed, for better or for worse, over the course of the study.

For just over half of the participants, fiber intake dropped by about 3 grams for every 1,000 calories consumed daily. For the remaining individuals, fiber intake increased by about the same amount. The associated changes in belly fat were noteworthy: in those whose fiber intake increased over the two years, their belly fat decreased by about 4%. But in people whose fiber intake fell, their belly fat increased by a much larger amount, 21%.

Latino participants were used because people of this ethnicity are more prone to weight gain around the middle. Davis says, however, that increasing fiber intake would probably have an effect on just about anybody – the level of impact might just be different.

“Even slight decreases in dietary fiber are having a pretty significant metabolic impact,” she says. The author recommends that all young people try to increase their fiber intake by 6 grams per day, which is “not an unrealistic goal for kids to set.” The recommended daily fiber intake is about 25 to 30 grams per day for young people. However, Davis urges people to read labels for nutrition information before purchasing foods: “Just because it says 'whole wheat' or 'multigrain' doesn't mean it's a good source of fiber. People think if it's brown, if it's wheat, it's good, but not necessarily."

The study was published in the November issue of the American Journal of Clinical Nutrition.