Abstract
Personal behavior patterns, such as unhealthy diet and lack of physical activity, lead to the development of overweight and obesity. These are associated with other comorbidities, reduced quality of life, premature frailty and increased mortality. Personalized web-based interventions are promising in inducing behavioral change leading to effective reductions in body weight at relatively low costs. However, the long-term effects have not been thoroughly investigated. This work evaluates the effectiveness of web-based interactive weight loss coaching and compares it to a non-interactive web-based health program. Therefore, a randomized controlled trial (RCT) was implemented, measuring primary and secondary outcomes at four time points (program start; end of the 12-week-program; 6 months after program end, 12 months after program end). The net sample covered 1499 subjects in the intervention group and 1492 in the control group. On average, the IG was 43 years old (±13.6), 80.1% male, and had 86.4 kg body weight (±16.1) at baseline. The CG was 42.7 years old (±13.9), 79.5% male and had a mean body weight of 86.1 (±15.7). Multilevel analyses with fixed effects were carried out both from the perspective of an intention-to-treat (ITT) and a complete cases approach (CCA). In sum, our adjusted models suggest a weight loss of 0.4 kg per time point. At the end of the program, significant differences in weight loss in % to baseline (delta M = 1.8 in the CCA) were observed in favor of the intervention group. From a long-term perspective, no superiority of the intervention group in comparison to the control group could be found. More intensive use of the program was not statistically associated with higher weight loss.