Five-year follow-up of a randomized weight loss trial on a digital health behaviour change support system.

Background: The weight regain after successful weight loss is a common challenge. This study aimed to assess the long-term effectiveness of a web-based health behaviour change support system (HBCSS) utilizing persuasive systems design (PSD) and methods of cognitive behavioural therapy (CBT). We have previously demonstrated the two-year effectiveness of the HBCSS.

Methods: In total, 532 participants with overweight or obesity (BMI 27-35 kg m^-2) were split into three groups with different intensities of intervention: CBT-based group counselling, self-help guidance (SHG), and usual care. These groups were further divided into HBCSS and non-HBCSS groups. The HBCSS was a 52-week programme. The follow-up took five years in total.

Results: Mean weight change (%) (95% CI) from baseline among HBCSS and non-HBCSS users was 1.5 (-0.02 to 2.9), p = 0.056 and 1.9 (0.3-3.3), p = 0.005, respectively, at five years. Of the six groups, the SHG group without HBCSS had a statistically significant increase in weight (%) from baseline at five years (3.1, 95% CI 0.6 to 5.6, p = 0.010). The other groups did not have a significant increase in weight. There was no significant difference between groups at five years in weight. Fewer blood pressure medications were started over the five-year period in HBCSS group (p = 0.046).

Conclusion: The 12-month HBCSS intervention was not able to maintain reduced weight better than non-HBCSS at 5 years. However, there were significant weight difference favouring HBCSS over the whole 5-year period. The decrease in the need for antihypertensives suggests that the significant weight loss by HBCSS at early years has a health-promoting legacy effect.