Emergence of the obesity epidemic preceding the presumed obesogenic transformation of the society

Abstract

The obesity epidemic, evolving in many countries since the 1970s, has been attributed to the widespread contemporary so-called obesogenic transformation of the societies, but what preceded the epidemic? Using quantile regression, we studied the trends by year of birth in the percentile distribution of body mass index (BMI = weight/height²) of 320,962 Danish school children, born from 1930 to 1976, and of 205,153 Danish young conscripts, born from 1939 to 1959. The overall trend of the percentiles of the BMI distributions were found to be linear across the years of birth. While the percentiles below the 75th were almost stable, those above showed a steadily steeper rise the more extreme the percentile among both school children and young men is. These changes, indicating the emergence of the obesity epidemic, preceded the presumed obesogenic transformation of the society by several decades and imply that other, so far unknown, factors have been involved.

Fig. 1.. Changes by year of birth of observed BMI percentiles in young men.

Selected BMI percentiles (0.1, 0.25, 0.5, 0.75, 0.9, 0.95, and 0.99) for young men born from 1939 to 1959 and examined at the draft boards in the Copenhagen region at age 18 to 26 years.

Fig. 2.. Changes by year of birth of quantile regression estimates of BMI percentiles in young men.

Selected quantile regression–based estimated linear (lines) and nonlinear (dots) BMI percentiles (0.1, 0.25, 0.5, 0.75, 0.9, 0.95, and 0.99) for young men born from 1939 to 1959 and examined at the draft boards in the Copenhagen region at age 18 to 26 years.

Fig. 3.. Quantile regression–based slopes of each linear BMI percentile per year of birth among children.

Estimated slopes of linear changes in BMI percentiles of girls and boys at ages 7, 10, and 13 years by year of birth from 1930 to 1976. Slopes (kg/m² per year) are on the y axis for each percentile from the 1st to the 99th of the BMI distributions (with gray zones around each dot indicating 95 percent confidence intervals, only visible at the highest percentiles).

Fig. 4.. Quantile regression–based slopes of each linear BMI percentile per year of birth among young men.

Estimated slopes of linear changes in BMI percentiles of young men around age 19 by year of birth from 1939 to 1959. Slopes (kg/m² per year) are on the y axis for each percentile from the 1st to the 99th of the BMI distributions (with gray zones around each dot indicating 95 percent confidence intervals).