Background: Dairy foods may play a role in the regulation of body weight.

Objective: We examined the association between changes in dairy product consumption and weight change over 9 y.

Design: The study was conducted in 19 352 Swedish women aged 40-55 y at baseline. Data on dietary intake, body weight, height, age, education, and parity were collected in 1987-1990 and 1997. The intake frequencies of whole milk and sour milk (3% fat), medium-fat milk (1.5% fat), low-fat milk and sour milk (<or=0.5% fat), cheese, and butter were calculated at baseline and follow-up. The women were categorized into 4 groups according to their intake: 1) constant, <1 serving/d; 2) increased from <1 serving/d to >or=1 serving/d; 3) constant, >or=1 serving/d; and 4) decreased from >or=1 serving/d to <1 serving/d. Odds ratios (ORs) with 95% CIs for an average weight gain of >or=1 kg/y were calculated by using multivariable logistic regression analyses, with group 1 as the reference.

Results: Mean (+/-SD) body mass index (in kg/m2) at baseline was 23.7 +/- 3.5. The constant (>or=1 serving/d) intakes of whole milk and sour milk and of cheese were inversely associated with weight gain; ORs for group 3 were 0.85 (95% CI: 0.73, 0.99) and 0.70 (95% CI: 0.59, 0.84) respectively. No significant associations were seen for the other 3 intake groups. When stratified by BMI, the findings remained significant for cheese and, for normal-weight women only, for whole milk and sour milk.

Conclusion: The association between the intake of dairy products and weight change differed according to type of dairy product and body mass status. The mechanism behind these findings warrants further investigation.