Accuracy of Self-Report Versus Objective Smart-Scale Weights During 12-Week Weight Management Intervention.

OBJECTIVE: Greater frequency of self-weighing has been associated with greater weight loss in weight management interventions, but little is known regarding the accuracy of self-reported weight data.

METHODS: Agreement between objective smart-scale and self-reported weight data was assessed in 74 adults (age = 50.7 years; BMI = 31.2 kg/m2 ) enrolled in a 12-week, Internet-based weight management program. Participants were asked to self-weight daily using a study-provided smart scale and to self-report weights via the study website.

RESULTS: There was strong agreement between smart-scale and self-reported weight values (intraclass correlation = 0.982) but only moderate agreement regarding frequency of self-weighing assessed via each method (κ = 0.491; P < 0.0001). Greater self-weighing frequency was associated with greater weight loss across measures (all P < 0.001). Compared with days when participants did both, weights were 0.66 kg higher on days when participants self-weighed via the smart scale but did not self-report weight (8% of days) and 0.58 kg higher on days when they self-reported weight but did not self-weigh via the smart scale (4% of days; all P < 0.0001).

CONCLUSIONS: Results suggest that self-reported weight values are similar to smart-scale measurements; however, either method alone may underestimate self-weighing frequency. Furthermore, missing self-weighing data should not be treated as ignorable because weights may be higher than those observed on nonmissing days.