Six Facts About Belly Fat

5. Work It Out. Naturally it helps to exercise, but not just because any abdominal-strengthening activity will lead to a flatter belly. Exercise also reduces stress and insulin levels. "If insulin levels go up, cortisol, which is a counter-regulatory hormone, goes up as well," says Yale's Dr. Katz. "More fat means more insulin; more insulin means more counter-regulatory hormones, which means more fat in the belly."

6. Foods to Avoid. While there's no single culprit, there are food ingredients that can make it harder to lose weight around your waist. Trans fats seem to promote abdominal fat deposition and the apple body shape, says Lawrence Rudel, professor of pathology and biochemistry at the Wake Forest University School of Medicine. (Trans fats are in some margarines, crackers, cookies and other foods made with partially hydrogenated oils.) In a study, Rudel found that trans-fat fed monkeys deposited 30 percent more fat in their abdomens than monounsaturated-fat fed monkeys.

7. Belly-Fat Fighting Foods. "It's too much responsibility to put on any one food," says Drewnowski. "One thing to have a flat belly is to have low body fat, period. If you have no body fat, you will have a flat belly—but also a flat behind." (But, for a temporarily flatter belly—say, for a bikini day—avoid bulky, high-volume foods such as salads, says Drewnowski. Some coffee, which contains the diuretic caffeine, will also get rid of extra water and give extra slimness for the day.)

As for long-term benefits, there may be no magic bullet foods, but there are some foods that may help if they're part of a healthy diet, and others that are simply good for your cardiovascular system, which is especially important if you tend to gain abdominal fat. Here's a quick rundown:

Whole Grains. In a study published earlier this year in the American Journal of Clinical Nutrition, researchers at Penn State compared 25 obese adults eating whole grains vs. 25 obese adults eating refined grains, for 12 weeks. Both groups lost the same amount of weight (an average of eight to 11 pounds), but the whole-grain eaters lost double the fat in the belly area. Good sources of whole grains: whole-grain cereal, oatmeal, brown rice and barley, says registered dietitian Heather Katcher, coauthor of the Penn State study. One possible reason is that whole grains contain more fiber, which helps slow digestion and prevent blood sugar from increasing too quickly and, as a result, helps keep insulin levels lower. She adds that lower insulin levels appear to decrease fat-cell size in the abdominal region. However, whole grains are no panacea, you still have to make other healthy lifestyle choices.

Tart Cherries. Try a "tart heart smart diet," says Dr. Steven F. Bolling, professor of cardiac surgery at the University of Michigan and coauthor of a recently presented study that showed tart-cherry enriched diets reduced "central adiposity," (fat around your middle) along with inflammation and triglycerides (known risk factors for type 2 diabetes and cardiovascular disease) in rats. The anthocyanins in tart cherries are probably what made rats who ate them (in powdered form) less likely to gain weight as belly fat, he says. Like apples and oats, cherries are a good source of soluble fiber, which seems to lower insulin levels. It can't hurt to eat cherries. "They're tasty," says Bolling. "I eat 'em."