Evidence from epidemiology shows and inverse association between dairy intake and body weight. That this effect might be due to the calcium content of dairy is supported by a similar inverse association between calcium and body weight. The mechanisms by which calcium or diary might be effective at preventing weight gain are unknown, but might relate to appetite regulation through modulation of calcitonin, the presence of the lipolytic substance conjugated linoleic acid in dairy foods, the suppression of 1,25 dihydroxyvitamin D by calcium, or the insulinotropic effects of the whey fraction of milk. That multiple mechanisms of action are responsible for the beneficial effects of dairy on weight gain is supported by abundant evidence in the form of animal studies and human clinical trials that have investigated the cellular changes resulting from high calcium or dairy intakes.
Calcium and dairy products may also influence substrate oxidation and energy expenditure in the postprandial state. For example, some clinical trials have reported increases in fat oxidation with calcium and dairy intakes, suggesting that shifts in metabolic pathways occur with increased intake. Administration of high calcium meals increases postprandial fat oxidation when compared to low calcium meals, via a mechanisms unrelated to diet induced thermogenesis. It is unclear at present how calcium or dairy could increase fat oxidation, but for dairy, it may related to changes in the release of insulin following consumption. This could related to changes in glycaemic index of ingested carbohydrate caused by the slow release of the milk protein casein from the stomach. This may decrease glycaemia and reduce the area under the curve for plasma insulin, thus increasing fat oxidation.
Another interesting finding of some clinical trails is the increase in faecal fat content associated with high calcium diets. One study found a 2.5 fold increase in fat excretion in the faeces with a high calcium diet. This may result from the formation of soluble soaps that impair fat absorption in the small intestine. The reduced fat absorption may result in a small energy deficit that ultimately leads to weight loss. Some evidence also suggests that dairy can alter postprandial lipid metabolism because it causes a decrease in fat absorption. Overall, results of clinical trials suggest that diary and calcium can help weight loss, but only for certain individuals. High dairy or high calcium diets appear to be effective at accelerating fat loss for those who are overweight or obese, have calcium intakes below 600md/d, and those who address their calorie imbalance to favour weight loss.
RdB
