title: Slowing down of adult body mass index trend increases in England: a latent class analysis of cross-sectional surveys (1992-2010).
abstract: BACKGROUND
  The prevalence of excess body weight, commonly measured as body mass index (BMI)≥25 kg m(-2), has increased substantially in many populations worldwide over the past three decades, but the rate of increase has slowed down in some western populations.
  
  
  OBJECTIVE
  We address the hypothesis that the slowing down of BMI trend increases in England reflects a majority sub-population resistant to further BMI elevation.
  
  
  METHODS
  Pseudo-panel data derived from annual cross-sectional surveys, the Health Surveys for England (1992-2010). Trends in median BMI values were explored using regression models with splines, and gender-specific mixture model (latent class analysis) were fit to take an account of increasing BMI distribution variance with time and identify hidden subgroups within the population.
  
  
  METHODS
  BMI was available for 164 155 adults (men: 76 382; women: 87 773).
  
  
  RESULTS
  Until 2001, the age-adjusted yearly increases in median BMI were 0.140 and 0.139 kg m(-2) for men and women, respectively, decreasing thereafter to 0.073 and 0.055 kg m(-2) (differences between time periods, both P-values<0.0001). The mixture model identified two components--a normal BMI and a high BMI sub-population--the proportions for the latter were 23.5% in men and 33.7% in women. The remaining normal BMI populations were 'resistant' with minimal increases in mean BMI values over time. By age, mean BMI values in the normal BMI sub-population increased greatest between 20 and 34 years for men; for women, the increases were similar throughout age groups (slope differences, P<0.0001).
  
  
  CONCLUSIONS
  In England, recent slowing down of adult BMI trend increases can be explained by two sub-populations--a high BMI sub-population getting 'fatter' and a majority 'resistant' normal BMI sub-population. These findings support a targeted, rather than a population-wide, policy to tackle the determinants of obesity.
authors.affiliation: Institute of Population Health, Medical Research Council Health eResearch Centre (HeRC), University of Manchester, Manchester, UK.
authors.forename: M
authors.initials: M
authors.lastname: Sperrin
authors.affiliation: CCSR, School of Social Sciences, University of Manchester, Manchester, UK.
authors.forename: A D
authors.initials: AD
authors.lastname: Marshall
authors.affiliation: CCSR, School of Social Sciences, University of Manchester, Manchester, UK.
authors.forename: V
authors.initials: V
authors.lastname: Higgins
authors.affiliation: Institute of Population Health, Medical Research Council Health eResearch Centre (HeRC), University of Manchester, Manchester, UK.
authors.forename: I E
authors.initials: IE
authors.lastname: Buchan
authors.affiliation: Institute of Cancer Sciences, Medical Research Council Health eResearch Centre (HeRC), University of Manchester, Manchester, UK.
authors.forename: A G
authors.initials: AG
authors.lastname: Renehan
mesh_terms: D000328:Adult; D000368:Aged; D001823:Body Composition; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D004739:England / Q000453:epidemiology; D005260:Female; D006306:Health Surveys; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology*; D015995:Prevalence