Shift in the composition of obesity in young adult men in Sweden over a third of a century.

OBJECTIVE: To assess whether the composition of the obese category (body mass index (BMI)> or =30) has changed during the last one-third of a century in young adult men.
DESIGN: Retrospective study of 1,580,913 men (18.3+/-0.4 years) representing 82% of the Swedish male population at military conscription age between 1969 and 2005. Measured height and weight were used to define moderate and morbid obesity as BMI 30-34.9 and > or =35, respectively. Data on socio-economic position (SEP), place of residence (urban, semi-urban and rural), age and test center were also collected.
RESULTS: From the period 1969-1974 to 2000-2005, the prevalence of moderate obesity almost quintupled (0.8-3.8%; P<0.0001), while morbid obesity increased 10-fold (0.1-1.3%; P<0.0001). The composition of the obese category changed from 12.9 to 25.1% morbidly obese during the same time, corresponding to an annual growth in the odds of 2.8% (CI(95%) 2.5-3.1%) per year within the obese category. Compared to 1969-1974, the odds ratios of obesity and morbid obesity, respectively, were 1.6 (1.6-1.7) and 1.9 (1.7-2.2) in 1980-1984, 2.8 (2.7-2.9) and 4.0 (3.5-4.5) in 1990-1994, and 6.0 (5.7-6.3) and 11.4 (10.1-12.9) in 2000-2005, after adjustment for SEP, urban/rural place of residence, age and test center. Extrapolation of the growth rate during the observation period resulted in an estimated 4% morbidly obese in 2020.
CONCLUSION: Morbid obesity increased faster than moderate obesity during the last 35 years. As the health risks and costs of obesity-related morbidity increase disproportionately in the morbidly obese, it is important to assess morbid obesity in prevalence studies, and distinguish the morbidly from the moderately obese in cost analyses.