Published Papers - Abstract 195

Brown WJ, Williams L, Ford JH, Ball K & Dobson AJ. Identifying the 'energy gap': Magnitude and determinants of five year weight gain in mid-age women. Obesity Research, 2005; 138: 1431-1441

Objective: The aims of this study were to estimate average yearly weight gain in mid-age women, and to identify the determinants of weight gain, and of gaining weight at double the average rate. Research Methods and Procedures: The study sample comprised 8071 participants (aged 45-55 years) in the Australian Longitudinal Study on Women's Health who completed mailed surveys in 1996, 1998 and 2001. Results: On average the women gained almost 0.5 kg per year [average 2.42 kg (95% CI:2.29-2.54) over 5 years]. In multivariate analyses, variables associated with energy balance (physical activity, sitting time and energy intake), as well as quitting smoking, menopause / hysterectomy, and baseline BMI category were significantly associated with weight gain, but other behavioural and demographic characteristics were not. After adjustment for all the other biological and behavioural variables, the odds of gaining weight at about twice the average rate (more than 5kg over 5 years) were highest for women who quit smoking (OR=2.94; 95% CI: 2.17, 3.96). There were also independent relationships between the odds of gaining >5kg and (1) lower levels of habitual physical activity; (2) more time spent sitting; (3) energy intake, (but only in women with BMI > 25 at baseline); (4) menopause transition and (5) hysterectomy. Discussion: The average weight gain equates with an energy imbalance of only about 10kcal or 40kJ per day, which suggests that small sustained changes in the modifiable behavioural variables could prevent further weight gain.