Time-based physical activity interventions for weight loss: a randomized trial.

Abstract

This study aims to examine whether enhancing standard behavioral weight loss interventions (standard behavioral weight loss program (SBWP)) with additional strategies at the initiation of intervention (ADOPT) or providing the additional strategies at predetermined times over the intervention period (MAINTAIN) enhances 18-month weight loss. This was a clinical trial of participants (N = 195; mean ± SEM: age, 43.2 ± 8.6 yr; body mass index, 33.0 ± 3.4 kg·m) randomized to SBWP, ADOPT, or MAINTAIN. All participants were prescribed an energy-restricted diet and physical activity, with group intervention sessions delivered over 18 months. ADOPT participants received additional phone contact (months 1-3), supervised exercise (months 1-6), and behavior campaigns (months 4-9). MAINTAIN participants received additional phone contact (months 4-6), supervised exercise (months 7-12), and behavior campaigns (months 13-18). There was a significant group-time interaction for weight loss (P = 0.0032). SBWP participants lost 9.3 ± 0.9, 7.8 ± 1.1, and 5.9 ± 1.2 kg at 6, 12, and 18 months, respectively. ADOPT participants lost 8.9 ± 0.9, 7.6 ± 1.2, and 5.8 ± 1.2 kg, whereas MAINTAIN participants lost 9.7 ± 0.9, 11.0 ± 1.2, and 9.0 ± 1.2 kg at 6, 12, and 18 months, respectively. The group-time interactions for SBWP versus MAINTAIN (P = 0.0033) and for ADOPT versus MAINTAIN (P = 0.0075) were significant. There was a significant group-time interaction for change in fitness (P = 0.0060). The group-time interaction for MAINTAIN versus ADOPT (P = 0.0018) was significant, with a trend for MAINTAIN versus SBWP (P = 0.0525). MAINTAIN improves 18-month weight loss compared with SBWP and ADOPT, with statistical trends indicating that MAINTAIN results in greater improvements in fitness. These results suggest that time-based strategies emphasizing physical activity confer greater benefits when delivered later and over the full course of intervention. This provides valuable information for the implementation of time-based strategies for improving long-term weight loss and fitness in overweight and obese adults.