The study looks set to continue the debate about whether dairy foods can promote weight loss, and what the mechanism behind such an effect could be.
Writing in the American Journal of Clinical Nutrition, lead author Magdalena Rosell and her colleagues from the Karolinska Institutet in Stockholm looked at the intake of whole, sour, medium-and low-fat milk, as well as cheese and butter for 19,352 Swedish women aged between 40 to 55 at the start of the study.
Rosell and her colleagues collected data on dietary intakes at the start of the study (1987-1990) and again at the end (1997). Average body mass index (BMI) of the women was 23.7 kg per sq m at baseline. The women were subsequently divided into one of four intake groups: a constant less than one daily serving; an increasing intake from less than one to at least one daily serving; a constant intake of at least one daily serving; and a decreasing intake from at least one daily serving to less than one.
The researchers report that a regular and constant intake of whole milk, sour milk and cheese was significantly and inversely associated with weight gain, while the other intake groups were not. A constant intake of at least one daily serving on whole and sour milk was associated with 15 per cent less weight gain, while cheese was associated with 30 per cent less weight gain, said Rosell.
"The association between the intake of dairy products and weight change differed according to type of dairy product and body mass status," concluded the researchers. "The mechanism behind these findings warrants further investigation."
Since no effect was observed for the medium- and low-fat dairy products this raises questions about the effect of calcium on the weight loss. Talking to Reuters Health, Rosell suggested that conjugated linolenic acid (CLA) found in dairy could aid weight control, but stressed that insufficient evidence exists to support such a conclusion.
The study does have notable limitations, namely the use of self-reporting of intakes. The authors were also unable to discern if women who had started to gain weight switched to lower fat dairy products or reduced intakes, meaning no causal link could be determined.
A previous study from Purdue University claimed that young women could burn more calories if they ate three or four dairy servings per day. However another report, also from Purdue, reported that increased dairy consumption had no effect on weight gain or loss.
On the other hand, Dr. Michael Zemel from the University of Tennessee told attendees at last year's Paris Anti-Obesity Therapies 2006 conference that dairy can help reduce body fat and that calcium only accounts for about 40 per cent of the effect.
Dairy industries in Europe and the US have been promoting milk-based products for consumers who want to slim for some time but the new findings underline that further work needs to be done to support such claims.
Source: American Journal of Clinical Nutrition Volume 84, Number 6, Pages 1481-1488 "Association between dairy food consumption and weight change over 9 y in 19 352 perimenopausal women" Authors: M. Rosell, N.N Hakansson and A. Wolk