Obesity is a complex disease and its underlying aetiology is not fully understood. However, research has consistently reported anti-obesity effects for dietary calcium. Administration of calcium to rodents and humans with calorie restriction appears to causes a decrease in abdominal body fat and also a decrease in body weight. Increasing calcium intake from 400 to 1200 mg/d during a 500 kcal/d energy restriction has been shown to increase fat loss and weight loss by 26 and 38 %, respectively. However, the fact that calcium seems to alter the partitioning of energy from adipose tissue to lean mass even in the absence of energy restriction infers that calcium might increase insulin sensitivity in some way. Increasing calcium intake therefore has beneficial effects on weight loss. However these effects appear to be greater when the calcium is supplied as dairy products, possibly because dairy contains additional factors that aid weight loss.
Epidemiological evidence has consistently demonstrated an inverse association between dairy and calcium intakes with body weight. In addition, a large number of clinical trials have shown weight loss effects for both calcium and dairy products. For example, researchers1 have compared the effects of a diet containing 1100 mg/d of calcium from yoghurt with a diet containing 400 to 500 mg/d of calcium from non-dairy sources, on the weight loss in 38 obese adults during a -500 kcal/d energy deficit. During the study the authors made an effort to control the daily micronutrient and fibre intakes of the two groups to prevent confounding effects. The results showed that fat loss was significantly increased on the yoghurt diet (-4.43 kg) when compared to the non-yoghurt diet (-2.75 kg). This fat loss resulted in a significantly greater loss of trunk fat from the yoghurt group (-3.99 cm), when compared to the non-yoghurt diet (-0.58 cm).
These results support the growing body of evidence that indicates calcium is beneficial at causing weight loss in obese individuals. In this study, the calcium was in the form of dairy, and from previous data it can be suggested that the weight loss experienced by the subjects would have been less if non-dairy calcium supplements had been used. The reason for this is not clear, but may relate to the conjugated linoleic acid present in dairy products, which has been shown to be beneficial to weight loss. Alternatively it might relate to the casein content of dairy, which may delay gastric emptying and reduce the glycaemic effects of foods. Consumption of yoghurt in this study resulted in the subjects losing an additional 22 % body weight and 61 % more body fat, when compared to the non‑dairy diet. Interestingly, the yoghurt diet caused a significant reduction in the loss of lean tissue (-1351 g), when compared to the normal calcium diet (-1968 g).
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