Body mass index (BMI) data for men and for women of age 18 and over from the Health Survey for England (HSE) is analysed to investigate the changes in adult BMI in England since the early 1990s. A method is devised for producing estimated population BMI distributions, and these distributions give much more detailed information than just using the standard BMI categories. Topics include the changes in BMI over time, how BMI varies with age, a model for producing BMI scenarios, calorie values for the BMI changes, and how BMI varies across different categories of deprivation.

General findings include: the way that BMI has increased over time is approximately a linear scaling transformation, which means that BMI has increased much more for those with a higher BMI than those with a lower BMI; BMI increased at a faster rate in the 1990s than since then; the BMI distributions for men and women are very different, but have increased in a similar way over time; within narrow birth cohorts, mean BMI tends to increase with age for all ages with the fastest rate of increase being for the youngest ages; the age 18 distributions are very similar for men and women and are the lowest BMI values with about two thirds in the healthy BMI category; the BMI distribution increases with age in different ways for men and women; model scenarios were able to be produced for the continuation of current conditions and for returning to the lower BMI levels of the early 1990s; the increases in daily calorie amounts calculated for the BMI changes using models from the literature are quite small; BMI tends to be higher for categories of greater deprivation with the differences being particularly large for the data for women.