It cuts your risk of heart disease and helps control your diabetes — and helps you weigh less. Is it a new miracle drug? Not by a long shot. It's whole-grain food.

It's clear that hearty, whole-grain foods are good for you. They seem, well, too heavy to be a diet food. But in the long term, those who eat lots of whole grains weigh less than those who avoid these fiber-rich foods.

The finding comes from a huge study of health professionals at the Harvard School of Public Health in Boston. Researchers Pauline Koh-Banerjee, ScD, and colleagues analyzed diet and health records from more than 27,000 of these 40- to 75-year-old men.

The bottom line: Eating 40 grams of whole grains a day cuts middle-age weight gain by as much as 3.5 pounds. The report appears in the November issue of the American Journal of Clinical Nutrition.

"All it takes is about 1 cup of oatmeal, or 3/4 cup of brown rice, or several slices of brown bread each day," Koh-Banerjee tells WebMD. "With all the popularity of low-carb diets, people think that all carbs are bad. But there are good carbs that not only protect your health but reduce your waistline."

Previous studies have shown that eating whole grains cuts men's and women's risk of heart disease and diabetes. But this is the first study to link whole grains with lower weight.

"Men who increase their consumption of whole grains gain less weight than other men," says Koh-Banerjee, now an assistant professor at the University of Tennessee Health Science Center in Memphis. "It did not stop them from gaining weight, but protected against overweight."

Whole Grains More Than Just Fiber

Whole grains have three parts: bran, germ, and the starchy endosperm. Refined grains are stripped of bran and germ. This takes away nearly all the fiber and nutrients and leaves behind nearly all the calories.

Somehow, all three parts of whole grains work together. "The whole grain is greater than the sum of its parts," Koh-Banerjee says.

Nutritionist Leslie Bonci, MPH, RD, says that there are good reasons weight watchers should love whole grains. Bonci is director of sports nutrition at the University of Pittsburgh Medical Center and serves as nutritional consultant to professional and college sports teams and to dancers in the Pittsburgh Ballet Theatre company.

"Whole grains are high in fiber. Fiber is important for gastrointestinal function — and it makes you more full, so you don't eat as much," Bonci tells WebMD. "The human body uses more calories to break down high-fiber foods. And whole grains are a little bit higher in protein, a little higher in fat content. People worry about the fat, but this extra protein and extra fat also contribute to that feeling of being full."

Koh-Banerjee says researchers are just beginning to learn why whole grains are so good for you.

"What the science is finding is it is not just the bran, not just the fiber," she says. "We are finding more and more nutrients in the whole grain. This is why it is so important to consume the whole grain. There is so much in it. We are still uncovering just what many of those benefits are."

Discovering Whole-Grain Foods

Dark breads may come to mind when you think of whole grains. Most breads don't contain as much whole grain as brown rice, toasted wheat cereals, or oatmeal. But even foods with lower whole-grain content add up to good nutrition — and lower weight.

"Some of the really rich sources of whole grain are brown rice, oatmeal, toasted wheat cereals, even popcorn," Koh-Banerjee says. "But as long as you are consuming whole grains, you will get healthful effects."

The FDA says foods can be labeled "whole grain" if they contain 51 percent whole grain by weight. Looking for this label is a good way to find healthy foods — but foods with at least 25 percent whole grain are also linked to lower weight, Koh-Banerjee says.

Koh-Banerjee says she and her colleagues are working to have food labeled with the gram amount of whole grains they contain.

By Daniel J. DeNoon, reviewed by Brunilda Nazario, MD

SOURCES: Koh-Banerjee, P. American Journal of Clinical Nutrition, November 2004; vol 80: pp 1237-1245. Pauline Koh-Banerjee, ScD, assistant professor, University of Tennessee Health Science Center, Memphis. Leslie Bonci, MPH, RD, director, sports nutrition, University of Pittsburgh Medical Center.