How accurate are recalls of self-weighing frequency? Data from a 24-month randomized trial

BACKGROUND: Self-weighing is an important component of self-monitoring during weight loss. However, methods of measuring self-weighing frequency need to be validated. This analysis compared self-reported to objective weighing frequency. METHODS: Data came from a 24-month RCT. Participants received 12 months of a behavioral weight loss program and were randomly assigned to: 1) daily self-weighing, 2) weekly weighing, or 3) no weighing (excluded from analysis). Objective weighing frequency was measured by Wi-Fi enabled scales and self-reported weighing frequency was assessed every 6 months by questionnaire. Objective weights were categorized to match the scale of the self-report measure. RESULTS: At 12 months, there was 80.8% agreement between self-reported and objective weighing frequency (weighted kappa = 0.67, p < 0.001). At 24 months, agreement decreased to 48.5% (kappa = 0.27, p < 0.001). At both time points where disagreements occurred, self-reported frequencies were generally greater than objectively assessed weighing. Both self-reported and objectively assessed weighing frequency were associated with weight loss at 12 and 24 months (p’s < 0.001). CONCLUSIONS: Self-reported weighing frequency is modestly correlated with objective weighing frequency; however, both are associated with weight change over time. Objective assessment of weighing frequency should be used to avoid overestimating actual frequency.