The effects of stress on body weight: Biological and psychological predictors of change in BMI

Objective: To investigate individual differences in the effects of stress on BMI. Research Methods and Procedures: Participants were 71 healthy women volunteers enrolled in a university-based nurse practitioner program. Predictors of change in BMI were hypothesized to be cortisol secretion, dietary restraint, bingeing, mastery, mood, and eating attitudes. Measures were made at the beginning of the academic semester and 12 weeks later during the participants' examination period. Results: The women were of normal weight (BMI 25.2 +/- 4.3) for their age [43; standard deviation (SD), 7]. By the examination period, 40 had gained weight (mean, 5.5 pounds; SD, 2.2), 19 lost weight (mean, 2.5 pounds; SD, 1.5), and 12 had stable weight. BMI, salivary cortisol secretion, bingeing behavior, depression, and anxiety increased significantly, whereas scores on dietary restraint, weight, shape, and eating concerns, and mastery decreased significantly. Regression analysis showed that change in daily cortisol secretion significantly predicted change in BMI and that mastery significantly moderated this relationship. However, a reduction in dietary restraint was a perfect mediator of this relationship. Change in cortisol secretion also significantly predicted change in dietary restraint, and this was moderated by dietary restraint at the beginning of the academic semester. Reduction in dietary restraint was also predicted by a reduction in mastery and weight concern. Discussion: We identified individual differences that confer vulnerability to weight gain during stressful life events (dietary restraint and mastery). Given that women are exposed to daily stressors and use cognitive strategies to restrain their dietary intake, increasing awareness of the role of stress on eating behavior and weight is an important goal.