If you had to choose either diet or exercise, which would you pick? If you're tempted to curb your eating habits without moving more, that might not be best to tackle the fat beneath your muscles and around your organs.

According to a University of Illinois study, it is exercise that shrinks the cells, known as visceral fat, more efficiently.

Researchers found that moderate exercise alone reduced inflammation in belly fat in mice. Now, that doesn't mean that if you keep chowing down on ice cream and pizza and run 30 minutes a day you're going to get a taut tummy. But it is a promising find for those who are at high-risk for heart disease and Type 2 diabetes.

In the study, mice were fed a high-fat diet for six weeks to induce mild obesity before being divided into four groups, a high-fat diet sedentary group, a high-fat diet exercise group, a low-fat diet group and a low-fat diet group with exercise. The exercise groups did the equivalent of a 30- to 45-minute walk in humans.

The combination of diet and exercise surprisingly didn't yield dramatically better results than diet or exercise alone. Plus, the only significant increase in belly fat after six to 12 weeks was found in the sedentary mice, which suggests that exercise, even with a fatty diet, can reduce the accumulation of visceral fat.

Because the study was only six to 12 weeks, the mice did not slim down significantly. "Even if they didn't lose weight, they still had improvements in metabolic parameters. That's an important message, too," says Vicki Vieira, co-author of the study. "Important metabolic changes were found even when the fat loss is very minimal."

"Which is better? Diet or exercise? I don't think there's really a good answer," says Vieira. "I think that both are really important contributions to whole body metabolic function. If an individual has a really hard time exercising or has a hard time sticking to a certain diet, for those people who get discouraged saying they're not going to do anything, any little bit helps. If it's exercise or walking 30 minutes a day, do what you do to see benefits."