Brief self-efficacy scales for use in weight-loss trials: Preliminary evidence of validity

Self-efficacy is a commonly included cognitive variable in weight-loss trials, but there is little uniformity in its measurement. Weight-loss trials frequently focus on physical activity (PA) and eating behavior, as well as weight loss, but no survey is available that offers reliable measurement of self-efficacy as it relates to each of these targeted outcomes. The purpose of this study was to test the psychometric properties of brief, pragmatic self-efficacy scales specific to PA, healthful eating and weight-loss (4 items each). An adult sample (n = 1,790) from 28 worksites enrolled in a worksite weight-loss program completed the self-efficacy scales, as well as measures of PA, dietary fat intake, and weight, at baseline, 6-, and 12-months. Confirmatory factor analysis supported the hypothesized factor structure indicating, 3 latent self-efficacy factors, specific to PA, healthful eating, and weight-loss. Measurement equivalence/ invariance between relevant demographic groups, and over time was also supported. Parallel growth processes in self-efficacy factors and outcomes (PA, fat intake, and weight) support the predictive validity of score interpretations. Overall, this initial series of psychometric analyses supports the interpretation that scores on these scales reflect self-efficacy for PA, healthful eating, and weight-loss. The use of this instrument in large-scale weight-loss trials is encouraged.