Children who drink more than three servings of milk each day are prone to becoming overweight, according to a large new study that undermines a heavily advertised dairy industry claim that milk helps people lose weight.

The study of more than 12,000 children nationwide found that the more milk they drank, the more weight they gained: Those consuming more than three servings each day were about 35 percent more likely to become overweight than those who drank one or two.

"The take-home message is that children should not be drinking milk as a means of losing weight or trying to control weight," said Catherine S. Berkey of Harvard Medical School and Brigham and Women's Hospital in Boston, who led the study, the largest to examine the question in children.

The National Dairy Council has spent $200 million since 2003 to promote the idea that milk can help people lose weight. Some research has suggested that calcium or other elements in milk may cause the body to make less fat and speed its elimination, but the studies produced mixed results.

"I went into this project expecting that drinking milk would have some weight benefit for children. So I was surprised when it turned out the way it did," said Berkey, whose findings are being published in the June issue of the journal Archives of Pediatrics & Adolescent Medicine. "The studies are all over the place, but the dairy industry tells children and adults, 'Drink more milk and you will lose weight.' I think that's misleading."

The dairy industry disputed the idea that the new study challenges its ads, saying it had said only that adults may be able to lose more weight if they drink milk while cutting calories.

"Our message has always been very conservative -- that three servings a day as part of a reduced-calorie diet may help promote weight loss," said Isabel Maples, a dietician speaking for the council. "Most children don't even get one serving a day" of milk.

Based on the findings, Berkey and her colleagues said children should follow federal recommendations to consume two to three servings of dairy a day, no more.

The study comes amid intense concern about the growing problem of obesity among children. The percentage of young people who are overweight has more than tripled since 1980. Public health experts have been particularly concerned that drinking soda contributes to weight problems, leading some parents to try to get their kids to drink more milk instead.

The researchers analyzed whether the children would have been better off if they replaced the soda they were drinking with milk but found no benefit.

"Our findings do not suggest that if children replace beverages sweetened with sugar with milk they would reduce their body weight," Berkey said.

For the study, Berkey and her colleagues analyzed data collected from about 12,829 children from all 50 states who were ages 9 to 14 in 1996, when they began participating in the Growing Up Today Study, an ongoing project examining the relationship between diet, exercise and a host of health issues.

The researchers examined the relationship between the children's milk intake between 1996 and 1999 and their weight over a one-year period. Those who drank more than three eight-ounce servings of milk a day gained the most weight, even after the researchers took into consideration factors such as physical activity, other dietary factors and growth. The association held, even though most of the children were drinking low-fat milk.

"That was surprising," Berkey said. "Apparently this applies to any kind of milk."

Several researchers agreed that the findings undercut the idea that milk promotes weight loss.

"There's been a lot of talk recently that somehow calcium in dairy products improves your ability to lose weight. There's certainly no evidence of that in this study," said F. Xavier Pi-Sunyer, a Columbia University obesity researcher.

Others, however, said a growing body of evidence supports the idea.

"There are a number of studies that show a positive effect of milk," said Michael B. Zemel of the University of Tennessee, who receives some funding from the dairy industry. "Increasing dairy augments the effects of cutting calories."

The National Dairy Council claims drinking milk helps people lose weight.