Background

To examine the impact of in-class and outside-class program components on weight loss in an online weight loss program.

Methods

Participants (N=28,833, mean age 50, 77% women, 77% Non-Hispanic White; 60% with obesity, 32% with overweight) were from employers and health plans. We examined percent weight loss at 12 weeks by class attendance (online) and outside-class activities (OCA; skill checks, meal logging, online community participation, goal setting, physical activity tracking, and weight logging). Class attendance tertiles (lessons/week) were: low 0 - 3.3; moderate 3.4-5.5 and high >=5.6. OCA were classified into even tertiles (low=T1, moderate=T2, high=T3) and a composite score was calculated.

Results

Participants in T3 OCA lost more weight than those in T1 OCA, regardless of class attendance. Weight loss for T3 vs T1 was 5.4% vs. 2.7% for the high in-class tertile and 5.2% vs 2.5% for the moderate in-class tertile (p<0.001). In contrast, class attendance had less influence: Weight loss for high vs low in-class tertiles was 3.7% vs. 3.6% for T2 OCA, and 2.7% vs. 2.5% for T1 OCA (p<0.001).Weight logging was associated with the greatest weight loss. For those who weight logged >=4x weekly vs <1.5x weekly, the absolute weight loss difference was 1.53% (p<0.001). Other OCA were only modestly associated with weight loss.

Conclusions

Participation in OCA predicted weight loss whereas in-class attendance did not. Those in the highest OCA tertile had 50% greater weight loss at 12 weeks than the lowest OCA group. Weight logging predicted greatest weight loss.