Maintaining the outcomes of a successful weight gain prevention intervention in mid-age women: two year results from the 40-something randomized control trial

Despite the life stage of menopause being identified as a high risk for weight gain, there are few obesity prevention interventions for this target group, and no evidence on maintenance of intervention effects after intervention support is withdrawn. In the 40-Something Randomized Controlled Trial (RCT) (ACTRN12611000064909), a five-consultation health professional (dietitian and exercise physiologist) obesity prevention intervention, using motivational interviewing principles (MI) over 12 months, achieved significantly greater weight loss than a self-directed intervention (SDI) (tailored written material) in 54 non-obese (body mass index (BMI): 18.5-29.9 kg/m²), premenopausal women (44-50 years). The aim of the current paper is to report on whether the intervention effects were maintained at two years. Anthropometric, biochemical and health behavior data were collected at baseline, 12 months (end of intervention) and 24 months (end of maintenance period). Forty participants (22 = MI, 18 = SDI) who completed all measures to 12 months were invited to participate in the monitoring phase and 30 (MI = 16, SDI = 14) consented. The primary outcome of weight at 24 months was assessed using intention to treat principles (n = 54), adjusting for baseline weight. The MI group had a significantly lower weight at 24 months (64.6 kg, 95% CI: 63.2, 66.6, p = 0.015) compared with the SDI group (67.3 kg, 95% CI: 65.7, 68.8), and the secondary outcomes of percentage body fat and waist circumference were also significantly lower in the MI group. The low-intensity, health professional weight control intervention utilizing MI principles was more efficacious in maintaining a significant weight loss compared to a self-directed intervention, and both were successful in preventing obesity.