A systematic review and meta-analysis by Abrguouel and colleagues, published in the International Journal of Obesity, appears to bring some clarity to this issue.
The paper reviews and analyses data from 16 randomised controlled trials on the the effect of dairy consumption on weight, body fat mass, lean mass and waist circumference (WC) in adults.
While there was no overall effect of increasing dairy intake on on body weight (-0.61 kg), there were some positive effects on reducing fat mass (0.72 kg), gain in lean mass (0.58 kg), and reduction in waist circumference (2.19 cm).
However, subgroup analysis showed that simply increasing dairy intake without also restricting energy intake has little to no effect on these paramerters.
It is only when dairy intake is increased in the context of a calorie-restricted diet that one sees a greater fall in body weight (1.29 kg), decrease in fat mass (1.11 kg), and decreased in waist circumference (2.43 cm) than in controls.
Thus, it appears that any beneficial effects of increasing intake of dairy products on body weight and composition is limited to the inclusion of dairy products in energy-restricted weight loss diets. Simply increasing your intake of dairy products may not be enough to decrease body weight.
On the other hand, whether or not ingesting an adequate (eucaloric) amount of dairy products may also help prevent weight gain remains to be seen.
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Abargouei AS, Janghorbani M, Salehi-Marzijarani M, & Esmaillzadeh A (2012). Effect of dairy consumption on weight and body composition in adults: a systematic review and meta-analysis of randomized controlled clinical trials. International journal of obesity (2005) PMID: 22249225