The accuracy of weight reported in a web-based obesity treatment program

The overall goal of the study was to understand the accuracy of self-reported weight over a 6-month Web-based obesity program.

As part of a larger study, subjects (n=323; 93% female; 28% African American) were randomized to a 6-month Internet-based behavioral weight loss program with weekly group meetings delivered either: (1) entirely by online synchronous chats or (2) by a combination of online chats plus monthly in-person group sessions. Observed weights were obtained at 0 and 6 months for all participants. Self-reported weights were submitted weekly to the study Web site. Differences in Observed and Reported weights were examined by gender, race, and condition.

Observed and Reported weight were significantly correlated at 0 and 6 months (r=0.996 and 0.996, ps <0.001 respectively). However, Reported weight underestimated Observed weight by 0.86 kg (p<0.001) at 6 months. Further, there was a significant weight loss effect (p<0.001) with those losing more weight more accurately estimating their Reported weight at 6 months. Additionally, 6-month Reported weight change differed from Observed weight change (difference=0.72 kg, p<0.001), with weight change using Reported weights estimating a slightly larger weight loss than Observed weights.

In general, the accuracy of self-reported weight is high for individuals participating in an Internet-based weight loss treatment program. Accuracy differed slightly by amount of weight lost and was not improved with periodic in-person assessment. Importantly, weight change by self-report was comparable to observed, suggesting that it is suitable for Web-based obesity treatment.