Dairy products and other calcium-containing foods and supplements don’t prevent weight gain, according to a 12-year study of thousands of middle-aged men. But some scientists maintain that the finding has no bearing on the dairy industry’s claim that dairy consumption promotes weight loss in people who cut back on calories.
Controversy about calcium’s role in weight management has grown since a study in 2000 suggested that it facilitates weight loss (SN: 4/29/00, p. 277: Calcium may become a dieter’s best friend). Obesity researcher Michael B. Zemel of the University of Tennessee in Knoxville, who led that dairy-industry–funded study, has since reported that other constituents of dairy products augment calcium’s fat-shedding effect.
Last year, the Physicians Committee for Responsible Medicine, a nonprofit group in Washington, D.C., sued several food companies and dairy-industry groups over advertisements claiming that dairy products aid weight loss. The group’s president, Neal D. Barnard, says that the results of most of the relevant studies conflict with the findings of Zemel and other industry-funded researchers. The lawsuit is pending.
In the newly reported, federally funded test, epidemiologist Swapnil N. Rajpathak of the Albert Einstein College of Medicine in New York City and his colleagues at Harvard University tracked more than 19,000 men, age 40 and older, from 1986 until 1998. Every 4 years, each volunteer completed a questionnaire about his body weight and dietary habits. The average weight gain during the study was nearly 3 kilograms.
In an initial analysis of the data, men with the highest calcium intake experienced a lower-than-average weight increase of about 2.5 kg, Rajpathak and his colleagues report in the March American Journal of Clinical Nutrition. However, many of those men exercised more or consumed fewer calories than other volunteers did.
Among men who exercised similar amounts and had similar caloric intakes, the researchers found no association between weight gain and calcium or dairy intake. In fact, Rajpathak says, men with the largest increase in high-fat dairy intake over the 12 years gained slightly more weight than the men who decreased their high-fat dairy intake did.
The new finding “confirms that the weight of the evidence is against dairy products having any weight-loss effects at all,” says Barnard.
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But Madelyn H. Fernstrom, director of the Weight Management Center at the University of Pittsburgh Medical Center, says that the study doesn’t address whether, “if you cut back your calories and replace some of your remaining calories with dairy, you will lose weight at a faster rate … than if you’re simply cutting back your calories.”
In a previous dairy-industry–supported study, Robert P. Heaney of Creighton University in Omaha, Neb., says that he found that “there is a calcium effect, but it’s a small effect.” He says that questionnaires provide only rough estimates of dietary intake, leading to uncertainty that may have masked a small, beneficial effect of calcium intake in the new study.