June 6, 2005 -- A growing body of research is taking aim at the claim that there is something special about milk and other dairy foods that help people lose weight.
In a study published in April, women who added extra milk to their diets for a year lost no more weight than women who consumed the same number of calories, but drank less milk. Now a new study in older children and teens shows that drinking more than the recommended three servings of milk a day actually promotes weight gain. But the dairy industry doesn't see it that way.
Harvard Medical School researcher Catherine S. Berkey, ScD, who led the research team, says the evidence regarding milk and weight loss is far from conclusive.
"Studies examining the relationship between milk and body fat have been very mixed, but the marketing messages directed at families are clear -- advertisements encourage dairy products such as milk to help promote weight loss, so it is critical we continue to study this area until we have solid answers," Berkey says.
What the Ads Say
The American Dairy Council's "24/24 -- Milk Your Diet, Lose Weight!" campaign makes the claim that drinking three servings of milk a day, as part of a reduced-calorie diet "may help you lose more weight and burn more fat than cutting calories alone."
"A growing body of evidence shows that when people include three servings of milk a day -- or 24 ounces in 24 hours -- in a reduced-calorie diet, they lose significantly more weight than people who don't," the Council's weight loss web site states. "The studies suggest that the mix of nutrients found in milk, such as calcium and protein, may help improve the body's ability to burn fat -- particularly around the middle."
The campaign is based largely on a 2004 study by University of Tennessee nutrition researcher Michael Zemel, PhD, who has since published the book The Calcium Key: The Revolutionary Diet Discovery That Will Help You Lose Weight Faster.
Zemel's study included 32 obese people who followed different reduced-calorie diets for six months. He reported that people who consumed three to four servings of milk or other dairy products a day lost more weight than those who took in the same number of calories but ate less dairy.
'A Calorie Is a Calorie'
The research was funded by the Dairy Council and an interview with Zemel appears on the Council's weight loss web site.
"When your body doesn't get enough calcium, it starts a defense mechanism to preserve what calcium it does have," he is quoted as saying. "It's actually a hormonal response that increases the amount of fat stored and slows down the process that breaks it down for energy. So if you increase calcium, less fat is stored and more fat is burned."
But nutrition expert Alice Lichtenstein, DSc, tells WebMD that she has seen nothing to convince her that any single nutrient or nutrient mix holds the key to easy weight loss.
Lichtenstein directs the Cardiovascular Nutrition Laboratory at Boston's Tufts University.
"There just isn't convincing evidence that any combination of foods or nutrients helps people burn fat quicker," she says. "You can't beat the system. When it gets right down to it, the best evidence that we have right now suggests that a calorie is a calorie."
The New Research
In the newly published research, Berkey and colleagues from Boston's Brigham and Women's Hospital and Harvard Medical School analyzed data from a large study of obesity in adolescents in an attempt to assess the impact of milk and other dairy products on weight.
The researchers tracked the health and dietary habits of almost 13,000 children between the ages of 9 and 14 for three years starting in 1996.
In a previous analysis the researchers reported that kids who drank a lot of sugary sodas and fruit drinks gained more weight than those who didn't. Berkey tells WebMD that the decision to look at dairy products stemmed, in part, from the Dairy Council's weight loss ad campaign.
The study is published in the June issue of the Archives of Pediatric and Adolescent Medicine.
"We found that the adolescents who drank more than three servings a day of milk over a one-year period were 25% more likely to become overweight during that year than adolescents who reported drinking two to three servings a day," she says.
Berkey says the kids who drank more than the recommended three servings a day of milk probably gained weight because they were taking in too many calories.
Most of the children in the study drank low-fat or nonfat milk. An average serving of low-fat milk has approximately 100 calories.
"Our study may suggest that it is not milk itself that is associated with weight gain, but the calories this beverage contains," she says. "The take-home message is that children should not be drinking milk as a means of losing weight or trying to control weight."
Daily Council Weighs In
Registered dietitian Theresa Wagner is a spokeswoman for the National Dairy Council. She tells WebMD that the study findings are not at odds with the council's message that three servings of milk a day is optimal.
"We aren't saying that more is better," she says. "The American Academy of Pediatrics has said for years that children should drink 24 ounces of milk a day, limit their juice intake to 6 to 8 ounces a day, and drink water for thirst. I think this study verifies this statement."
She adds that older children and teens are far more likely to drink too little milk than too much, and that the weight loss message is aimed at adults and not children.
"We are recommending what the dietary guidelines recommend, which is three servings of dairy a day," she says. "Milk is a nutrient-packed beverage, and teens, especially, aren't getting enough of the nutrients that are found in dairy products."