Disability pensions incur huge societal costs in many countries. In Sweden, the three greatest drivers of such productivity losses are musculo-skeletal, circulatory and psychiatric disorders, all closely associated with weight status. We identified 16 studies investigating the body mass index (BMI)–disability pension relation. In cross-sectional studies, a significantly greater proportion of obese compared with normal weight subjects were disability pensioners. In longitudinal studies, a J-shaped relation with BMI was generally found in both men and women of various ages. Different definitions of obesity status complicated interpretation, as several studies mixed the underweight and normal weight, which appear to have different disability pension risks. In middle-aged men, relative risks were elevated for circulatory causes only for the overweight and obese, while associations for mental disorders were similar in the underweight and overweight but much higher in the obese. In both sexes, monotonic increases and decreases were seen for circulatory and respiratory causes respectively. In intervention studies, reduced disability pension incidence and increased gainful employment were reported after surgery. In summary, BMI was significantly associated with disability pension, but the direction of causality may vary with underlying cause. Interventions had positive productivity effects in the morbidly obese, but whether this holds for the overweight remains to be proven.