National income and macro-economic correlates of the double burden of malnutrition: an ecological study of adult populations in 188 countries over 42 years

Background: The double burden of malnutrition (DBM) represents a growing global challenge with adverse health and economic consequences. We aimed to investigate the associative roles of national income (gross domestic product per capita [GDPPC]) and macro-environmental factors on the DBM trends among national adult populations. Methods: In this ecological study we assembled extensive historical data on GDPPC from the World Bank World Development Indicators database and population-level DBM data of adults (aged ≥18 years) from the WHO Global Health Observatory database in 188 countries over 42 years (1975–2016). In our analysis, a country was considered to have the DBM in a year when adult overweight (BMI ≥25·0 kg/m²) and underweight (BMI <18·5 kg/m²) prevalence was each 10% or more in that year. We used a Type 2 Tobit model to estimate the association of GDPPC and selected macro-environmental factors (globalisation index, adult literacy rate, female share in the labour force, share of agriculture in the national gross domestic product [GDP], prevalence of undernourishment, and percentage of principal display area mandated to be covered by health warnings on cigarette packaging) with DBM in 122 countries. Findings: We find a negative association between GDPPC and the likelihood of a country having the DBM. However, conditional on its presence, DBM level exhibits an inverted-U shaped association with GDPPC. We found an upward shift in DBM levels from 1975 to 2016 across countries at the same level of GDPPC. Among the macro-environmental variables, share of females in the labour force and share of agriculture in the national GDP are negatively associated with DBM presence in a country, whereas the prevalence of undernourishment in the population is positively associated. Further, globalisation index, adult literacy rate, share of females in the labour force, and health warnings on cigarette packaging are negatively associated with DBM levels in countries. Interpretation: DBM level in national adult populations rises with GDPPC until US$11 113 (in 2021 constant dollar terms) and then starts declining. Given their current GDPPC levels, most low-income and middle-income countries are thus unlikely to have a decline in the DBM levels in the near future, ceteris paribus. Those countries will also be expected to experience a higher DBM level at similar levels of national income than were historically experienced by the current high-income countries. Our findings point to a further intensification of the DBM challenge in the near future for the low-income and middle-income countries as they continue to have income growth. Funding: None.