posted on 2022-09-15, 12:09authored byKagenaar E., VanHemelrijck W.M.J., Kunst A.E., Janssen F.
Introduction: Cross-national comparison suggests that the timing of the obesity epidemic differs across
socio-economic groups (SEGs). Similar to the smoking epidemic, these differences might be described by
the diffusion of innovations theory, which states that health behaviours diffuse from higher to lower
SEGs. However, the applicability of the diffusion of innovations theory to long-term time trends in
obesity by SEG is unknown. We studied long-term trends in the obesity prevalence by socio-economic
group in England, France, Finland, Italy, Norway, and the USA and examined whether trends are
described by the diffusion of innovations theory.
Methods: Obesity prevalence from 1978 to 2019 by educational level, sex, and age group (25+) from
health surveys were harmonised, age-standardised, Loess-smoothed, and visualised. Prevalence rate
differences were calculated and segmented regression was performed to obtain annual percentage
changes, which were compared over time and across SEGs.
Results: Obesity prevalence among lower educated has exceeded that of higher educated groups,
except among USA men, in all countries throughout the study period. A comparable increase across
educational levels was observed until approximately 2000. Recently, obesity prevalence stagnated
among higher educated groups in Finland, France, Italy, and Norway, and lower educated groups in
England and the USA.
Discussion: Recent trends in obesity prevalence by SEG are mostly in line with the diffusion of
innovations theory, however, no diffusion from higher to lower SEGs at the start of the epidemic was
found. The stagnation among higher SEGs but not lower SEGs suggests that the latter will likely
experience the greatest future burden.