Dairy Connections to Healthy Weight Loss

Dairy Connections to Healthy Weight Loss

Epidemiological studies indicate that a high intake of dairy foods or calcium is associated with lower body weight, body-mass index and body fat. Dairy foods appear to have a more pronounced effect than calcium dietary supplements. Some studies have shown that dairy foods increase energy expenditure and fat oxidation in humans and may reduce appetite, while other trials have failed to confirm this. Recent studies also indicate that calcium may enhance weight loss efforts by binding up fats in the gut and preventing them from being absorbed.

The desire for additional long-term intervention studies is a major reason for skepticism by some on connecting dairy and weight loss. But for others, particularly in the United States where most of the studies have taken place, this work has been incorporated into consumer communications, such as the ‘Three-a-Day of Dairy’ campaign.

The effect is modest and not a magic bullet for the obese. But it does appear to be a factor in about 50 studies reporting the effect. What it means is that people on a modest calorie-controlled diet, and consuming 3 to 4 daily servings of dairy, will lose weight and fat more quickly than those restricting similar calories and consuming inadequate servings of dairy (<1 serving per day). Those on an unrestricted diet may gain less weight or body fat over time.

So, why the skepticism? One reason is the need to clarify the mechanism. Currently, there are four potential mechanisms for how dairy may affect weight and fat loss:

1. The formation of insoluble fatty acid soaps in the lumen of the small intestine leading to decreased absorption and higher fetal excretion (as hypothesised by Prof. Arne Astrup’s work in Denmark).

2. A decrease in serum calcitriol concentration that leads to a reduction in the influx of calcium into adipocytes, which creates an increase in lypolysis and a decrease in lypogenesis. The lower level of calitriol may also have a direct effect on the basal metabolic rate through its effects on endocrine mechanisms (as hypothesised by Dr. Micheal Zemel’s work in the U.S.).

3. The poor absorption of lactose leads to digestion of lactose through colon bacteria reducing energy intakes.

4. The association between high-dairy intake and high-protein intake, with protein having the effect of increasing thermogenesis and satiety (both ideas suggested by Dr. Gertjan Schaafsma from The Netherlands).

In practice, many agree that dairy’s effect on weight loss and weight management may be a combination of all these mechanisms.

GDP and a consortium of not-for-profit members are now seeking to clarify at least the first of these mechanisms by conducting a meta-analysis of the approximately 10-12 intervention studies that have been published. They will focus on dairy calcium intake in humans, affecting fecal fat and energy excretion, taking compliance, protein intake and other relevant factors into consideration (using meta-regression analysis).

The study will involve scientists from the U.S., The Netherlands and Denmark who have expertise in dairy calcium and statistical meta-analysis methodology. The research will be sponsored by groups from the U.S., Europe and Australia. Leading the study group will be Prof. Arne Astrup of the Department of Human Nutrition at the University of Copenhagen, who also will serve as the senior author of the publication(s) resulting from the work. The study is expected to be completed within six months, at which point we will be better able to plan next steps.