Changes in the distributions of body mass index and waist circumference in English adults, 1993/1994 to 2002/2003

Background: Obesity rates have increased markedly in recent years. This study investigated whether increases in adiposity over the past 10 years in England reflect across-the-board gains in adiposity or differential effects in subgroups. Methods: The data were from the Health Surveys for England, which include home-based measurements of height, weight and waist circumference in population-representative samples. Mean-difference (m-d) curves were calculated to examine increases in BMI and central adiposity at selected percentile points across the distribution between 1993/4 and 2002/3. The sample comprised 20 246 participants in 1993/1994 and 11 708 in 2002/2003. Patterning of population adiposity was examined in relation to gender, age and socioeconomic status (SES). Results: Both BMI and central adiposity increased markedly more in the upper part of the distribution, with intermediate increases in the middle and little change at the lower end of the distribution. The patterning and magnitude of increases in adiposity were similar for men and women, and for lower and higher SES groups. Increases at the top of the distribution were greater for younger adults, with the 90th percentile of waist circumference increasing by more than 8 cm in 10 years in young women. Conclusions: Gains in adiposity have not been equivalent across the BMI distribution. Thinner people in 2002/3 were almost as thin as they were 10 years earlier, but fatter people were considerably fatter. This could represent progressively greater responsiveness to the 'obesogenic' environment in individuals with higher complements of susceptibility genes. These population trends have important implications for future health and services to manage severe obesity.