Milking the data: does dairy burn more fat? Don't bet your bottom on it

Nutrition Action Healthletter, Sept, 2005 by David Schardt

You've probably seen the ads in magazines or on TV. "Milk-cheese-yogurt. Burn more fat, lose weight." Drink 24 ounces of milk every 24 hours and that skinny hourglass figure will be yours. Eat three servings of yogurt every day and squeeze into that itsy-bitsy bikini.

Here's what the ads don't say:

* Only three small published studies have found greater weight loss in people who were told to cut calories and eat dairy foods, and all were done by one researcher with a patent on the claim.

* The government's expert nutrition advisory panel has called the evidence on dairy and weight loss "inconclusive."

* Two new studies have found that dairy foods don't help people lose weight.

But why blame the dairy folks? They probably didn't want to bog the ads down with too much detail.

The poor dairy industry. People consume far less milk than they used to. Soft drinks have stolen away teenage and adult customers. And nutrition experts routinely criticize the saturated fat in cheese.

Michael Zemel to the rescue. The University of Tennessee nutrition researcher comes armed with a few small studies in people, a book, and an idea (plus a patent) for selling dairy foods that even he admits sounds "pretty outrageous"--eating three servings of milk, cheese, or yogurt every day can help dieters lose weight.

Never mind that the studies are small and that no independent researchers have corroborated their findings. Producers have tons of milk and cheese to move.

Solution? Launch what the industry calls "a full court press of marketing activities" to capitalize on the weight-loss claim before the authorities catch up with you.

Hire the world's largest promotions agency. Pay celebrities like Dr. Phil McGraw to say in milk mustache ads that "drinking milk can help you lose weight." Give away 24 convertibles in 24 days to reinforce the idea that 24 ounces (3 cups) of milk ever 24 hours melts away fat. Launch "The Great American Weight Loss Challenge," a 12-week program centered around drinking 24 ounces of milk every day, and give $25,000 to the city that signs up the most dieters and $10,000 to a group that successfully completes the program.

And license Zemel's claim so that companies can use it to promote their dairy products for weight loss.

After two years and millions of dollars worth of advertising and giveaways, nearly half of American women say that they have heard that dairy foods help people lose weight.

If only there were sufficient evidence to back up the claim.

Theory, Theory on the Wall

In the early 1990s, Michael Zemel, a young nutrition scientist at Wayne State University School of Medicine in Detroit, was testing what happens when men with high blood pressure increase the amount of calcium they get by eating more dairy foods. After eating two cups of yogurt a day for a year, their blood pressures fell.

"But there was a result we didn't expect," Zemel recalls. The men lost an average of 11 pounds of body fat.

"It made no sense to me whatsoever," he says. "They didn't eat fewer calories and they didn't exercise more." But Zemel had no control group--men who ate no yogurt or a yogurt-like food without calcium--so he couldn't tell what was causing the weight loss.

Other research seemed to suggest that there was something to the calcium-fat link. Among participants in the third NHANES survey of Americans, for example, fatter people consumed less calcium than thinner people. (1) Of course, it's hard to know whether something else about people who consume less calcium--maybe they drink more soda pop-influenced their weight.

In the late 1990s, Zemel, now at the University of Tennessee in Knoxville, tested his theory on animals. In several studies, obesity-prone mice on high-sugar, high-fat diets gained less (or lost more) weight when given calcium than similar mice fed the same diet with very little calcium. Mice that were given milk did even better.

By 2000, Zemel was ready to test dairy foods on humans. "We put 32 overweight people on a balanced but calorie-restricted diet for six months, which reduced their daily food intake by 500 calories," he says.

Roughly a third of the 32 got the control diet, which consisted of, at most, one serving of dairy foods and 400 to 500 milligrams of calcium a day. Another third are the same diet, but got an extra 800 mg of calcium from pills, which brought them up to about 1,200 mg a day. The remaining third were told to substitute three servings of dairy foods for other foods on the diet, which also gave them around 1, 200 mg of calcium a day.

After six months, the three-dairy-a-day group had lost 24 pounds, the calcium-supplemented group 19 pounds, and the control group 15 pounds. (2)

With funding from General Mills, Zemel's research group followed up with a similar study using yogurt. They put 34 overweight people on a calorie-restricted diet. Roughly half got 400 to 500 mg of calcium a day from foods other than dairy. The other half got about 1,100 mg of calcium a day, most of it from eating three six-ounce servings of General Mills Yoplait Light.