The mortality risk of being overweight in the twentieth century: Evidence from two cohorts of New Zealand men.

How have health and social mortality risks changed over time? Evidence from pre-1945 cohorts is sparse, mostly from the United States, and evidence is mixed on long-term changes in the risk of being overweight. We develop a dataset of men entering the NZ army in the two world wars, with objectively measured height and weight, and socioeconomic status in early adulthood. Our sample includes significant numbers of indigenous Māori, providing estimates of weight and mortality risk in an indigenous population. We follow men from war's end until death, with data on more than 12,000 men from each war. Overweight and obesity were important risk factors for mortality, and associated with shorter life expectancy. However, the reduction in life expectancy associated with being overweight declined from 5 to 3 years between the two cohorts, consistent with the hypothesis that being overweight became less risky during the twentieth century.