Calcium and weight management

Several studies, primarily observational in nature, have linked higher calcium intakes to lower body weights or less weight gain over time. Two explanations have been proposed for how calcium may help to regulate body weight. First, high-calcium intakes may reduce calcium concentrations in fat cells by lowering the production of two hormones (parathyroid hormone and an active form of vitamin D), which in turn increases fat breakdown in these cells and discourages its accumulation. In addition, calcium from food or supplements may bind to small amounts of dietary fat in the digestive tract and prevent its absorption, carrying the fat (and the calories it would otherwise provide) out in the feces.

Dairy products in particular may contain additional components that have even greater effects on body weight than their calcium content alone would suggest. Three small, recently published clinical trials show that calcium-rich dairy products may help obese individuals following reduced-calorie diets to lose some excess weight and fat. In one trial, 32 obese adults were randomized to one of three groups: eating a standard diet providing 400-500 mg calcium, eating a standard diet supplemented with 800 mg calcium, and eating a diet with 3 servings/day of dairy products to provide 1,200-1,300 mg calcium. The subjects ate 500 fewer calories a day over the 24 weeks of the study. All lost weight and body fat, but those taking the calcium supplements lost significantly more than subjects eating the unsupplemented standard diet, and those on the high-dairy diet lost by far the most. Dairy products also favorably affected body composition in a small group of obese African-American adults who followed a weight-maintenance program for 24 weeks. Subjects who ate 3 servings/day of dairy products, which increased calcium intakes to 1,200 mg/day, lost significantly more fat (both total body and abdominal) and preserved lean body mass as compared to those who consumed less than one daily serving of these foods and 500 mg/day total calcium.

Despite the hopeful results of these studies, other recent clinical trials make it clear that the involvement of calcium and dairy products in weight regulation and body composition is complex, inconsistent, and not well understood. For example, one study in young women of normal body weight found that higher intakes of dairy products had no effect on weight or fat mass over the course of one year. Another study in which 100 overweight and obese pre- and post-menopausal women on reduced-calorie diets received either 1,000 mg/day calcium or a placebo for 25 weeks found no significant differences in weight or fat loss between the groups. Similar results were obtained in a study of 1,471 postmenopausal women (somewhat overweight on average) who were randomly assigned to take 1,000 mg/day calcium or a placebo for 30 months, though there was a trend toward greater weight loss in those who took the calcium supplement and whose calcium intakes from food averaged less than 600 mg/day. Clearly, larger clinical trials are needed to better assess the effects of calcium and dairy products on body weight, composition, and fat distribution.