OBJECTIVE: The combined effect of life-course influences on obesity development and thus their potential public health impact is unclear. We evaluated combined associations and predicted probabilities for early and adult life risk factors with central and general obesity in mid-adulthood. SETTING: 1958 British birth cohort. PARTICIPANTS: 4629 males and 4670 females with data on waist circumference. OUTCOME MEASURES: 45 year obesity measured via waist circumference, waist-hip ratio (WHR) and BMI. RESULTS: At 45 years, approximately a third of the population were centrally obese and a quarter were generally obese. Three factors (parental overweight, maternal smoking during pregnancy and adult inactivity) were consistently associated with central and general obesity. Predicted probabilities for waist obesity increased from those with none to all three risk factors (0.15-0.33 in men; 0.19-0.39 in women (ptrend<0.001)), with a similar trend for general obesity. Additional factors (adult smoking, low fibre and heavy alcohol consumption) were associated with WHR obesity, although varying by gender. Prevalence of risk factors was higher in manual than non-manual groups: for example, in men 38% versus 25%, respectively, had ≥2 risk factors for waist and general obesity. CONCLUSIONS: Early-life and adult factors that are amenable to change are highly prevalent and accumulate in association with central and general obesity in mid-adulthood. The increase in probabilities for mid-adult obesity associated with cumulative levels of risk factors suggests the potential for public health impact.