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

Nutrition Action Healthletter, Sept, 2005 by David Schardt

* Foods. Kraft has run television and newspaper ads encouraging consumers to burn fat by eating cheese (the ads were discontinued earlier this year). The front cover of Zemel's book says, "Enjoy cheese and your favorite dairy foods while you get thin."

Yet the 18 dairy-dieters in Zemel's Yoplait study ate yogurt, not cheese. And the 11 in his first study got at least half their dairy calcium from milk. (The rest came from some combination of yogurt and cheese.)

Zemel admits that he doesn't know how much cheese the 11 were eating, or whether cheese had any impact on how much weight or fat they lost. "I just don't have the data to answer the question," he says. "But I do caution people not to get all of their dairy from cheese, because I don't know that cheese by itself works."

If something in dairy foods helps people lose weight, Zemel's latest research suggests that it's not in cheese.

"From our work in mice, we've found that the more active components of dairy tend to be concentrated in the whey, rather than in the curds," he explains. Whey, which is in milk and yogurt, is discarded during the cheese-making process.

It's not just Kraft that has exaggerated Zemel's findings. There's no evidence to support the milk industry's claim that "more than a dozen research studies now support the finding that drinking 24 ounces of milk every 24 hours will help people lose more weight than just reducing their caloric intake."

None of Zemel's studies instructed people to drink 24 ounces of milk a day. And MilkPEP, the industry's non-profit Milk Processors Education Program--it was formed to boost milk consumption and it promotes the "24 ounces in 24 hours" claim--couldn't point us to a single study in which people did.

Beyond Zemel

"People have a funny sort of bias," says Steven Heymsfield, executive director of clinical sciences at the pharmaceutical firm Merck and former deputy director of the New York Obesity Research Center at St. Luke's-Roosevelt Hospital in New York City. "They like their own work better and they have ways of seeing things in it that others don't."

Before scientists accept the idea that eating more dairy foods helps people lose weight, cautions Heymsfield, "I think we need to see really good randomized trials from other people who don't have a vested interest in the results."

Since Heymsfield made those comments, two trials by other researchers found that people don't lose more weight when they eat more dairy foods.

Jean Harvey-Berino and her co-workers at the University of Vermont put 45 overweight, middle-aged men and women on a weight-loss diet, behavior modification program, and exercise regimen. Half of them were assigned to eat about one dairy food a day, while half were told to eat three to four servings a day. After six months, both groups lost the same amount of weight and body fat.

"A high-dairy diet does not substantially improve weight loss beyond what can be achieved in a high-quality behavioral intervention," says Harvey-Berino. Her results, which were presented at a scientific meeting last year, are about to be published.