Unequal obesity distributions among adult populations have been reported in low- and middle-income countries, but mainly based on data of women of reproductive age. Moreover, incorporation of ever-changing skewed BMI distributions in analyses has been a challenge. Our study aimed to assess magnitude and rates of change in BMI distributions by age and sex.

Shapes of BMI distributions were estimated for 2005 and 2010, and their changes were assessed, using the generalized additive model for location, scale and shape (GAMLSS) and assuming BMI follows a Box–Cox power exponential (BCPE) distribution.

Nationally representative, repeated cross-sectional health surveys conducted between 2005 and 2013 in Mexico, Colombia and Peru.

Adult men and non-pregnant women aged 20–69 years.

Whereas women had more right-shifted and wider BMI distributions than men in almost all age groups across the countries in 2010, men in their 30s–40s experienced more rapid increases in BMI between 2005 and 2010, notably in Peru. The highest increase in overweight and obesity prevalence was observed among Peruvian men of 35–39 years, with a 5-year increase of 21 percentage points.

The BCPE–GAMLSS method is an alternative to analyse measurements with time-varying distributions visually, in addition to conventional indicators such as means and prevalences. Consideration of differences in BMI distributions and their changes by sex and age would provide vital information in tailoring relevant policies and programmes to reach target populations effectively. Increases in BMI portend increases of obesity-associated diseases, for which preventive and preparative actions are urgent.