Milk intake is inversely related to obesity in men and in young women: data from the Portuguese Health Interview Survey 1998-1999

Objective: To assess the relationships between milk intake and body mass index (BMI) in a representative sample of the mainland Portuguese population. Design: Cross-sectional study. Setting: National Health Interview Survey 1998-1999. Average daily milk intake was calculated by a frequency questionnaire that also assessed the average volume of one serving. BMI was derived from the subject's reported height and weight. Subjects: A total of 17771 men and 19742 women aged >= 18 y. Results: In men, milk intake was inversely related to BMI (r = 0.10, P < 0.001), whereas the relationship in women was weaker (r = -0.06, P < 0.001). In men, prevalence of milk consumers was lower in obese (62%) and in overweight (68%) than in normal weight subjects (71%, P < 0.001). After adjusting for age, region, physical activity, smoking, number of meals and educational level, milk intake decreased with increasing BMI (adjusted mean +/- s.e.: 280 +/- 5, 266 +/- 5 and 246 +/- 7 ml/day for normal, overweight and obese subjects, respectively, P < 0.001), even after excluding subjects who did not consume milk (368 +/- 5, 353 +/- 6 and 346 +/- 8 ml/day, P < 0.02). In women, prevalence of milk consumers was lower in obese (71%) and in overweight (72%) than in normal weight subjects (76%, P < 0.001). In women younger than 55 y, milk intake decreased with increased BMI categories (291 +/- 9, 271 +/- 10 and 269 +/- 11 ml/day for normal, overweight and obese subjects, respectively, P < 0.001), whereas no relationship was found in the older group. Conclusions: Increased calcium intake is slightly but significantly negatively related with BMI in men and premenopausal women. The lack of relationship in older women might be due to the hormonal status, but awaits further investigation.