JMIR Publications

ABSTRACT

Background:

Goal setting aids health-related behaviour change, but the influence of different types of goals on weight loss remains unclear.

Objective:

To investigate the association between three measures of goals setting and weight change during a 12-week digital behavioural weight loss programme delivered across the UK.

Methods:

Prospective longitudinal analysis of 36,794 UK adults with a body mass index of ≥25 kg/m2 that enrolled in the programme. Measures of goal setting were self-reported at enrolment including percentage weight loss goal (<5%, 5-10%, or >10%); overall goal preference (low, medium, or high); and weight loss motivation (appearance, health, fitness, or self-efficacy). Weight was measured at 4, 12, and 24 weeks. To measure sustained weight change, the primary outcome was weight at 24 weeks, assessed using mixed-model repeated-measures analyses to explore the effect of goal setting adjusted for known confounders. We explored drop-out rates by goal and whether engagement mediated the association between goals and weight loss.

Results:

Of the 36,794 participants included in the cohort, 13.1% (n=4,818) reported weight at 24 weeks. Most participants set goals of 5-10% weight loss (64.3%), but setting goals for >10% weight loss was associated with larger weight loss (mean difference between 5-10% vs >10%: 5.21kg; 95% CI: 5.01, 5.41; P<.001). There was no difference between goals of 5-10% and <5% (mean difference: 0.59kg; 95% CI: 0.00, 1.18; P=.05). Appearance was the most prevalent motivational factor (40.1%), but health or fitness were associated with greater weight losses than appearance (mean difference health vs appearance: 1.40kg; 95% CI: 1.15, 1.65; P<.001 and mean difference fitness vs appearance: 0.38kg; 95% CI: 0.05, 0.70; P=.03). Goal preference had no clear association with weight loss. Engagement with programme components was a significant independent predictor of weight loss but not a mediator of the effect of goal setting. At 24 weeks, those who set goals of >10% were less likely to drop-out compared to those setting 5-10% goals (OR: 0.40; 95% CI: 0.38, 0.42; P<.001); those who liked to set overall high goals were more likely to drop-out compared to those with medium goals (OR: 1.20; 95% CI: 1.11, 1.29; P<.001); and those motivated by fitness or health were less likely to drop-out compared with those motivated by appearance (OR: 0.92; 95% CI: 0.85, 0.995; P=.038 , and OR: 0.84; 95% CI: 0.78, 0.89; P<.001, respectively).

Conclusions:

Setting higher and specific weight loss goals and being motivated by health or fitness were associated with greater weight loss and lower likelihood of drop-out. Randomised trials of setting these types of goals are needed to confirm causality.