Overweight and obesity continue to be leading public health concerns. In the U.S., recent research indicates that more than 66% of adults and 17% of children aged two–19 years are overweight or obese. Researchers estimate that if current trends continue, nearly half of the children in North and South America will be overweight by 2010.
Excess body fat increases the risk of premature death, coronary heart disease, type 2 diabetes, hypertension, stroke, some types of cancer and other debilitating conditions. Because of these health outcomes, as well as the adverse economic consequences of overweight and obesity, numerous government programs are focused on obesity prevention.
The cause of overweight and obesity is many-factored, and successful prevention or treatment depends on multiple actions. Although attention has focused primarily on reducing energy (calorie) intake and/or increasing energy expenditure (physical activity), a promising beneficial role for dietary calcium and dairy products in weight management has emerged. This article reviews the current scientific evidence, including human clinical, observational and animal model studies that have explored the relationship between the consumption of dairy foods and weight management, as well as plausible mechanisms by which dietary calcium in dairy products may favorably affect body weight, body fat and lean mass.
Controlled feeding studies in humans are considered the “gold standard” of proof and have provided the strongest evidence for a beneficial role of dairy foods and calcium on body weight and body fat. Since 1998, several clinical studies have evaluated the impact of calcium and/or dairy product consumption on body weight and fat loss. In many of these studies, overweight or obese adults (males, females, Caucasians, African-Americans) who followed moderately reduced-calorie diets for 12 or 24 weeks and increased consumption of dairy foods from one serving or less/day (inadequate calcium) to three servings/day (adequate calcium) experienced enhanced body weight and/or body fat loss, reduced abdominal (trunk) obesity and minimal loss of lean body mass, compared to those consuming little or no dairy. Moreover, the intake of dairy foods had a substantially greater effect on both weight and/or fat loss, compared to an equivalent amount of calcium alone.
Importantly, three physiological and dietary conditions were common in those studies showing favorable weight loss effects of dairy/calcium. First, all study subjects were obese or overweight. Secondly, the subjects’ habitual calcium intakes were low and inadequate (<600mg/day). Third, all subjects consumed moderately reduced-calorie diets to induce weight loss (i.e., 500Kcals/day fewer than necessary to maintain weight).
Dairy-rich diets appear to increase weight loss by targeting the fat compartment during calorie restriction, according to findings from a multi-center, 12-week clinical study in overweight and obese adults. In this study, consuming three servings a day of dairy foods (about 1,400mg total calcium/day) while restricting calories for weight loss (-500Kcal/day) resulted in significantly greater loss of body fat, trunk fat, waist circumference and a trend for greater weight loss, compared to groups receiving a low-calcium (~600mg/day) control diet or an elemental calcium-rich diet supplied by calcium supplements (~1,400mg total calcium/day). The elemental calcium-rich diet in this study had no significant effects on weight loss or body composition, compared to the low-calcium control diet. Another study has also reported no differences in weight and body fat loss in overweight and obese women supplemented with elemental calcium (1,200mg/day) and vitamin D (400IU/day), compared to a control low-calcium diet.
Some studies have not observed significant differences in body weight and fat reductions between inadequate dairy and adequate dairy intakes. In a one-year study of obese subjects, authors concluded that a diet with recommended dairy servings does not substantially improve weight loss beyond what can be achieved in a behavioral intervention. In another one-year study, which investigated the impact of moderate (two servings dairy/day) vs. adequate calcium/dairy intakes (four servings dairy/day) in obese subjects under caloric restriction, there were no significant differences in weight or body fat loss between the groups. However, in both of these studies, subjects consuming adequate dairy consumed, on average, more calories than those consuming lower amounts of dairy, but still lost equivalent amounts of body weight and fat.
A study in healthy, normal-weight young women who were on diets that did not restrict calories reported no significant differences in body fat or lean mass in those who increased calcium intake from 800mg/day up to 1,300-1,400mg/day through dairy products for one year, compared to those who maintained inadequate intakes. However, after one and a half years, women who continued to consume adequate dairy had significantly less body fat than those who remained on an inadequate calcium/dairy diet.
Taken together, these studies indicate that the impact of dairy foods on augmenting body weight and body fat loss depends on factors such as calorie intake, baseline calcium, or dairy food intake and initial body weight (i.e., overweight or normal weight).