Although calories still count, the study showed that obese adults who ate a high-dairy diet lost significantly more weight and fat than those who ate a low-dairy diet containing the same number of calories.

"If you compare a dairy-rich versus a dairy-poor diet you can nearly double the rate of weight and fat loss with the same level of calorie restriction," says researcher Michael Zemel, PhD, professor of nutrition and medicine at the University of Tennessee in Knoxville.

Zemel says the study also showed that eating three to four servings of dairy products a day is more effective at enhancing weight loss efforts than calcium supplementation alone with pills or calcium-fortified foods.

The study appears in the April issue of Obesity Research and was supported by the National Dairy Council.

Previous studies have already shown that dieters who eat a calcium-rich diet are more successful at losing weight, but this study indicates that it's more than just the calcium in dairy products that helps shed pounds.

"Calcium is a critical factor in controlling what your body does with calories, and dairy is an even more critical factor," says Zemel. "Without changing how many calories we take away, we can alter how much weight and fat you lose."

Dairy Products Beat Calcium for Weight Loss

In the study, researchers compared the effects of three different calorie-restricted diets on weight loss in 32 obese adults. Each of the participants reduced their daily calorie intake by about 500 calories per day for 24 weeks and were divided into three groups:

• High-dairy. Total calcium intake of 1,200-1,300 milligrams per day from three to four servings of dairy foods, specifically milk, hard cheese, and yogurt.
• High-calcium supplemented/low-dairy. Total calcium intake of 1,200-1,300 milligrams per day made up of no more than one serving of dairy per day plus an 800-milligram calcium supplement.
• Low-calcium/low-dairy. Total calcium intake of 400-500 milligrams per day with no more than one serving of dairy per day and a placebo supplement.

Researchers say participants were free to choose from fat-free, low-fat, and regular milk, cheese, and yogurt. They typically picked fat-free and low-fat milk and yogurt and regular cheeses, while keeping their overall fat intake the same.

Serving sizes were 8 ounces or a cup for milk and yogurt and 1.5 ounces of hard cheese (about the size of six dice) or 2 ounces of processed cheese, such as two slices of American cheese.

The study showed that all of the groups lost weight, but those who ate the dairy-rich diet lost the most with an average of 24 pounds compared with 19 pounds in the calcium supplement group and 15 pounds in the low-calcium/low-dairy group.

That translates to a loss of an average of 11% of total body weight for those in the high-dairy group versus 6% in the low-calcium/low-dairy group.

"What that means is that if you're including three to four servings of dairy in your diet, you can make a modest degree of calorie restriction as effective as a severe degree of calorie restriction," Zemel tells WebMD.

In addition, researchers found the high-dairy group lost significantly more body fat than those in the other groups, particularly from the midsection. Excess fat in the abdominal area has been linked to a higher risk of heart attack and other health problems.

Dairy's Role in Weight Loss

Previous studies have shown that calcium can boost weight loss by increasing fat breakdown in fat cells. But experts say this study suggests that taking in calcium from dairy products may actually improve on those effects.

"Dairy for some reason, yet unexplained, has a greater effect on fat loss and specifically trunk fat loss than does calcium alone," says Rachel Novotny, PhD, RD, professor and chair of the department of human nutrition, food, and animal sciences at the University of Hawaii in Manoa.

Although the bulk of dairy's weight-loss enhancing effects is caused by its calcium content, researchers say there are a variety of potential mechanisms that may explain those additional benefits and merit further research.

For example, Novotny says that some of the minerals in dairy products, such as phosphorous and magnesium, may enhance calcium's beneficial effects on fat breakdown within the cells. In addition, the proteins in dairy products may help preserve muscle and increase metabolism.

But Novotny and Zemel are careful to point out that the results shouldn't be interpreted as license to indulge in dairy products in hopes of spurring weight loss. They caution that the bottom line of successful weight loss is still burning more calories than you take in.

"The question is whether within those calories are there choices you can make that will enhance the results," says Novotny. "I think the findings suggest that dairy products and calcium can be helpful in preserving muscle, losing fat from the upper body, and actually enhancing the weight loss process."

SOURCES: Zemel, M.Obesity Research, April 2004; vol 12: pp 582-590. Michael Zemel, PhD, professor of nutrition, University of Tennessee, Knoxville. Rachel Novotny, PhD, RD, professor, chairwoman, department of human nutrition, food, and animal sciences, University of Hawaii, Manoa. WebMD Medical News "Calcium for Weight Loss?"