Got milk? And high hopes it will help you shed a few pounds? The dairy industry is counting on it, thanks in part to a $200 million ad campaign that confidently touts studies suggesting a connection between consuming dairy products and losing weight. But dieters might want to delay sporting milk mustaches for the moment.
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Though the National Dairy Council and the researchers it pays stand by their claims, few others have endorsed the dairy-diet link. Even some scientists whose research supports that idea say its conclusions are premature.
"The bulk of the studies suggest a possible role, but there are inconsistencies in the data," said Dr. David Ludwig, an obesity expert at Children's Hospital Boston. In a 2002 study, he found that dairy aided weight loss.
"My concern is the advertising claims by the Dairy Council have well outstripped the available data," he said.
Those claims have received wide attention since 2003, when a coalition of dairy groups launched what has become the "3-A-Day" campaign, which advises that three servings a day of dairy supports weight loss.
The federal government also recommends three dairy servings a day, but doesn't support the weight-loss claim.
The dairy campaign is based on research by Michael Zemel, a nutrition professor at the University of Tennessee who began studying the link between dairy and weight during the late 1980s. Since 2000, he has published several studies that found people who eat a lower-calorie diet and consume the recommended low- or non-fat dairy servings lose nearly twice the weight as those who only cut calories.
But his research often is misunderstood, Zemel says. It is not a case of drink milk, lose weight. It works only for people who eat a low-calorie diet and who are not already consuming three servings of dairy.
That's a bit more nuanced than the "Lose More Weight" and "Burn More Fat" emblazoned across the packaging of a growing array of dairy products, though Zemel says the industry's claims accurately represent his findings.
Nuanced or not, the claims seemed like good news to Pam Syms, a 50-year-old Concord, N.H., woman who loves dairy and wants to lose a little weight.
Since seeing the industry's television ads a few weeks ago, Syms has brought yogurt to work every day. So far, no change in her weight, but she's happy for an excuse to eat dairy without guilt.
"Since I do like dairy products so much, it was just an affirmation that, 'Yes, I can keep eating those things,'" said Syms, who admits that, nevertheless, she's skeptical of the claims.
So was Zemel. He said that in 1988 when he made the first surprising connection between dairy and weight loss, "I couldn't get behind it without more data. By 2005, I feel we have that data."
So does Greg Miller of the National Dairy Council. The industry waited years before launching its campaign, he said, wanting first to amass enough studies to ensure solid scientific footing.
Among those studies are a handful of randomized clinical trials, often considered the "gold standard" of science. All were funded by the Dairy Council, and most involved Zemel, who has received nearly $2.1 million from the group since 1998.
Zemel also has patented the claim that dairy boosts weight loss, meaning every company that uses a "Slim Down with Yogurt" or similar logo has to pay him and his university. Since 2000, the patent has generated about $500,000, half of which goes to Zemel and two other patent holders.
But it's not Zemel's science that has been criticized _ it's the dairy industry's conclusions from it.
Barry Popkin, an obesity expert at the University of North Carolina at Chapel Hill, praised Zemel as a good scientist, but said the dairy industry has overreached. "We have too many contradictions and nobody's decided what the truth is," he says.
It's not for lack of trying.
The committee of scientists who drew up the 2005 federal dietary guidelines found the data inconclusive. The Centers for Disease Control and Prevention and the American Heart Association came to a similar decision.
Dr. Walter Willett, a Harvard University nutrition expert whose recent research suggests dairy doesn't help weight loss, said Zemel's studies are too small to sustain the industry's claims.
"You need to look across all the evidence," he said. "The larger randomized trials that have been done, they don't show weight loss. If anything, they show weight gain."
In part because of those contradictions, the Physicians Committee for Responsible Medicine, which advocates a vegan diet, has filed a class-action lawsuit.
The suit, which says the industry is promising weight loss to bolster weak sales, wants a judge to block the dairy ad claims. The group says most studies on the subject indicate either no link or an adverse link between milk and weight.
That view was reflected in a 2002 review of other dairy-weight studies by Susan Barr, a University of British Columbia nutrition professor. She found most studies showed no connection and two showed weight gain.
How to explain the inconsistencies? Ludwig suspects it's not the dairy itself, but how it interacts with the diet.
Perhaps people who drink milk instead of soda, for example, eat fewer calories because milk is more filling. That also means that healthy eaters could end up with too many calories overall if dairy replaces healthy, lower-calorie foods, Ludwig says.
Others suggest that dairy eaters' overall healthier lifestyles could explain the weight loss. Some studies found that people who don't get enough calcium weigh more. But that might signal poor diet, rather than any special effect that dairy has on weight.
Whatever the reason, many scientists for now are putting their conclusions on hold as they await more evidence.
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