A new study from Purdue University counters the notion that dairy products encourage weight loss, an idea touted in dairy industry advertisements. Researchers assigned participants to one of three groups: (1) a control group that maintained its usual diet, (2) a medium-dairy group consuming 1000-1100 mg of calcium daily, or (3) a high-dairy group consuming 1300-1400 mg of calcium daily. Participants in the two dairy groups were instructed to compensate for the addition of dairy products by reducing consumption of other foods so as to keep their energy intake unchanged.

None of the groups lost weight. In fact, the high-dairy group gained 1.5 kg (3.3 lb) over the year, which was slightly (although not statistically significantly) greater than the weight gain in the control group (0.8 kg, 1.8 lb) and the medium-dairy group (0.8 kg, 1.5 lb).

Dairy products clearly did not facilitate weight loss. In fact, if the high-dairy group's experience continued in a similar fashion over a ten-year period, the average participant would have had a 15-kg (33-lb) weight gain from the average baseline weight of 62.4 kg (137 lb) to 77.4 kg (170 lb), leading to an average body mass index of 27.8, which puts the group well into the overweight range (BMI > 25). The control group's 10-year experience, if similar to the one-year result, would have been a gain of about half as much weight as the high-dairy group.

Gunther CW, Legowski PA, Lyle RM, et al. Dairy products do not lead to alterations in body weight or fat mass in young women in a 1-y intervention. Am J Clin Nutr 2005;81:751-6.

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