Relationships between body mass index and well-being in young Australian women

OBJECTIVE: To explore relationships between body mass index (BMI, kg/m(2)) and indicators of health and well-being in young Australian women. DESIGN: Population based cohort study-baseline cross sectional data. SUBJECTS: 14,779 women aged 18-23 who participated in the baseline survey o f the Australian Longitudinal Study on Women's Health in 1996. MEASUREMENTS: Self-reported height, weight, medical conditions, symptoms an d SF-36. RESULTS: The majority of women (68%) had a BMI in the range 18.5- <25; 12% had a BMI <18.5; 14% had a BMI in the range 25 - <30 and 6% had a BMI great er than or equal to 30. After adjustment for area of residence, age, educat ion, smoking and exercise, women in the highest BMI category (greater than or equal to 30) were more likely to report hypertension, asthma, headaches, back pain, sleeping difficulties, irregular periods, and more visits to th eir medical practitioner. They were also more likely to have given birth at least once, and less likely to report 'low iron'. Women with low BMI (<18. 5) were more likely to report irregular periods and 'low iron'. Mean scores on the SF-36 sub-scales for physical functioning, general health and vital ity were highest for women with BMI in the range 18.5-25. CONCLUSION: Acknowledging the limits of the cross-sectional nature of the d ata, the results show that the deleterious effects of overweight can be see n at a comparatively young age, and that BMI <25 is associated with fewer i ndicators of morbidity in young women. However, as BMI <18.5 is associated with low iron and irregular periods, care should be taken when developing s trategies to prevent overweight in young women, not to encourage women with healthy weight to strive for a lower BMI.