Interactive effects of job stress and body mass index on over-eating

Recent prospective evidence drawn from the Whitehall II cohort reported by Kivimäki et al. implies that stressful situations are related to decreased body weight in thin men and increased body weight in obese men, whereas no corresponding interactive effects are observed in women. The mechanism underlying this phenomenon remains unknown, and the purpose of this study was to confirm our hypothesis that the relevant mechanism is behavioral (e.g., over-eating).

The subjects of this survey were 607 Japanese workers (response rate: 60.5%) in four organizations. The questionnaire solicited demographic information and included the Bulimia scale of the Eating Disorder Inventory-EZ to measure tendencies toward over-eating as well as the Japanese version of the Effort-Reward Imbalance Questionnaire (ERIQ). Body mass index (BMI) was calculated on the basis of data obtained during medical check-ups. We tested for linear and interactive effects with hierarchical regression analyses.

BMI was significantly (p<0.05) associated with over-eating both univariately and after adjusting for age in both sexes. Significant (p<0.05) interactions showed that ERIQ effort scores and effort-reward ratios were more positively associated with over-eating in men with higher BMIs, and ERIQ reward and financial remuneration scores were more negatively associated with over-eating in men with higher BMIs. No corresponding interactive effects were observed among women.

The results demonstrate that stressful situations are more associated with over-eating in men with higher BMIs. This might explain, in part, the mechanism underpinning the interactive effects proposed by Kivimäki et al.