To study the demographic and clinical parameters of three different categories of obesity, with particular focus on a cohort of individuals with BMI ≥ 50 kg/m2, the fastest growing category of obesity.

Over 700 obese individuals were studied (186 with BMI = 30–39 kg/m2, 316 with BMI = 40–49 kg/m2 and 290 with BMI ≥ 50 kg/m2).

Median BMI was 51 kg/m2 for patients who reported onset of overweight before 15 years of age, 47 kg/m2 for patients who reported onset between 15 and 30 years, and 42 kg/m2 for patients who became overweight after 30 years of age. The BMI ≥ 50 kg/m2 group was notably younger than the group with BMI = 30–39 kg/m2 (44 (sd 11) years v. 50 (sd 15) years; P < 0·0001). Eighteen per cent of obese patients studied were considered metabolically healthy according to standard cut-off points for blood pressure, fasting glucose and lipid profiles. However, the proportion of metabolically healthy individuals was significantly higher in the BMI = 30–39 kg/m2 group than in the BMI = 40–49 kg/m2 and BMI ≥ 50 kg/m2 groups (31 % v. 17 % and 12 % respectively; P < 0·05 and P < 0·005). When compared with people of similar age in the general population, individuals with BMI ≥ 50 kg/m2 had lower rates of marriage (51 % v. 72 %) and a higher prevalence of unemployment (14 % v. 5 %).

The current study suggests that the increasing prevalence of childhood obesity worldwide will lead to many more individuals achieving a higher BMI at a younger age. Furthermore, an earlier onset of overweight does not appear to prevent the adverse metabolic health outcomes associated with extreme obesity.