Setting targets leads to greater long-term weight losses and 'unrealistic' targets increase the effect in a large community-based commercial weight management group

Background: Setting personal targets is an important behavioural component in weight management programmes. Normal practice is to encourage 'realistic' weight loss, although the underlying evidence base for this is limited and controversial. The present study investigates the effect of number and size of weight-loss targets on long-term weight loss in a large community sample of adults.

Methods: Weight change, attendance and target weight data for all new UK members, joining from January to March 2012, were extracted from a commercial slimming organisation's electronic database.

Results: Of the 35 380 members who had weight data available at 12 months after joining, 69.1% (n = 24 447) had a starting body mass index (BMI) ≥30 kg m^-2 . Their mean (SD) weight loss was 12.9% (7.8%) and, for both sexes, weight loss at 12 months was greater for those who set targets (P < 0.001). Those that set ≥4 targets achieved the greatest loss (P < 0.001). The odds ratio for weight loss ≥10% at 12 months was 10.3 (95% confidence interval = 9.7-11.1, P < 0.001) where targets had been set compared to none. At the highest quintile of target size, the size of the first target explained 47.2% (P < 0.001) of the variance in weight loss achieved at 12 months. The mean (SD) BMI reduction in those with a target >25% was 7.6 (4.0) kg m^-2 . A higher percentage of obese members did not set targets (P < 0.001) compared to those with a BMI <30 kg m^-2 .

Conclusions: Much of the variance in weight loss achieved in this population was explained by the number of targets set and the size of the first target. Although obese people were less likely to set targets, doing so increased the likelihood of achieving clinically significant weight loss and, for some 'unrealistic' targets, improved the results.