Obesity is associated with impaired health-related quality of life (QOL) and reduced productivity; less is known about the effect of dietary factors. The present study investigated how dietary behaviours, physical activity and BMI relate to weight-specific QOL and work productivity. The study was conducted in thirty-one small blue-collar and service industry worksites in Seattle. Participants were 747 employees (33·5 % non-White). Measures included self-reported servings of fruits and vegetables, dietary behaviours such as fast food consumption, Godin free-time physical activity scores, measured height and weight, Obesity and Weight-Loss QOL (OWLQOL) scores, and Work Limitations Questionnaire scores. Baseline data were analysed using linear mixed models separately for men (n 348) and women (n 399), since sex modified the effects. BMI was negatively associated with OWLQOL in both women (P < 0·001) and men (P < 0·001). The linear effect estimate for OWLQOL scores associated with a one-category increase in BMI was 30 (95 % CI 25, 44) % for women and 14 (95 % CI 10, 17) % for men. BMI was positively associated with productivity loss only in women (exp(slope) = 1·46, 95 % CI 1·02, 2·11, P = 0·04). Eating while doing another activity was negatively associated with OWLQOL scores in men (P = 0·0006, independent of BMI) and with productivity in women (P = 0·04, although the effect diminished when adjusting for BMI). Fast-food meals were associated with decreased productivity in men (P = 0·038, independent of BMI). The results suggest that obesogenic dietary behaviours and higher BMI are associated with decreased QOL and productivity to different degrees in women and men.