Association between Self-Weighing and Percent Weight Change: Mediation Effects of Adherence to Energy Intake and Expenditure Goals

Background: To date, no investigators have examined electronically recorded self-weighing behavior beyond 9 months or the underlying mechanisms of how self-weighing might impact weight change. Objective: Our aims were to examine electronically recorded self-weighing behavior in a weight-loss study and examine the possible mediating effects of adherence to energy intake and energy expenditure (EE) goals on the association between self-weighing and weight change. Design: This was a secondary analysis of the self-efficacy enhancement arm of the Self Efficacy Lifestyle Focus (SELF) trial, an 18-month randomized clinical trial. Participants/setting: The study was conducted at the University of Pittsburgh (2008-2013). Overweight or obese adults with at least one additional cardiovascular risk factor were eligible. Intervention: Participants in the self-efficacy enhancement arm were given a scale (Carematix, Inc) and instructed to weigh themselves at least 3 days per week or every other day. The scale date- and time-stamped each weighing episode, storing up to 100 readings. Main outcome measures: Weight was assessed every 6 months. Adherence to energy intake and EE goals was calculated on a weekly basis using paper diary data. Statistical analyses performed: Linear mixed modeling and mediation analyses were used. Results: The sample (n=55) was 80% female, 69% non-Hispanic white, mean (standard deviation) age was 55.0 (9.6) years and body mass index (calculated as kg/m²) was 33.1 (3.7). Adherence to self-weighing declined over time (P<0.001). From baseline to 6 months, there was a significant mediation effect of adherence to energy intake (P=0.02) and EE goals (P=0.02) on the association between adherence to self-weighing and percent weight change. Mediation effects were not significant during the second and third 6-month periods of the study. Conclusions: Objectively measured adherence to self-weighing declined over 18 months. During the first 6 months, self-weighing directly impacted weight change and indirectly impacted weight change through changes in energy intake and EE.