Physical Activity Self-Monitoring and Weight Loss: 6-Month Results of the SMART Trial

CONROY, M. B., K. YANG, O. U. ELCI, K. P. GABRIEL, M. A. STYN, J. WANG, A. M. KRISKA, S. M. SEREIKA, and L. E. BURKE. Physical Activity Self-Monitoring and Weight Loss: 6-Month Results of the SMART Trial. Med. Sci. Sports Exerc., Vol. 43, No. 8, pp. 1568-1574, 2011. Introduction: Weight loss has been associated with higher physical activity (PA) levels and frequent dietary self-monitoring. Less is known about how PA self-monitoring affects adherence to PA goals, PA levels, and weight change. Methods: The SMART Trial is a clinical weight loss trial in which 210 overweight adults were randomized equally to one of three arms: 1) paper record (PR), 2) personal digital assistant with self-monitoring software (PDA), and 3) PDA with daily tailored feedback message (PDA + FB). PA self-monitoring and adherence to PA goals were based on entries in weekly submitted diaries. PA levels were measured via self-report by the past 6-month Modifiable Activity Questionnaire at baseline and 6 months. Results: Data are presented on 189 participants with complete 6-month PA data (84% female, 77% white, mean age = 47.3 +/- 8.8 yr, mean body mass index = 34.1 +/- 4.5 kg.m(-2)). Median PA level was 7.96 MET.h.wk(-1) at baseline and 13.4 MET.h.wk(-1) at 6 months, with significant PA increases in all three arms. PDA + FB arm had a higher mean number of weekly self-monitoring entries than the PR arm (3.4 vs 2.4, P = 0.003) and were more likely to maintain high (i.e., 100%) adherence to PA goals over time than the PDA (P = 0.02) or PR arms (P = 0.0003). Both PA self-monitoring and adherence to PA goals were related to higher PA levels at 6 months. A higher mean rate of PA self-monitoring was associated with a greater percentage of weight decrease (rho = -0.49, P < 0.0001) at 6 months. Conclusions: PA self-monitoring and adherence to PA goals were more likely in participants in the PDA + FB arm and in turn predicted higher PA levels and weight loss.