Objective: To determine whether obesity in adults is related to seasonal or climatic conditions around the time of birth.
Subjects: 1750 men and women born in Hertfordshire between 1920 and 1930.
Measurements: Height and weight measured in the home by trained fieldworkers.
Results: Body mass index (BMI) rose with increasing birth weight in men and women. In men, BMI and the prevalence of obesity (BMI > or = 30 kg/m2) varied as a function of month of birth and was greater among those born in January-June than among those born in July-December. The relationship between birth weight and adult obesity was also stronger in those born in the first 6 months of the year or following cold winters than in those born in the last 6 months of the year or following mild winters.
Conclusions: These findings suggest that adult obesity is linked both to high birth weight and to early cold exposure. Consequently, exposures in early life may contribute to individual variation in susceptibility to obesity in adults.