Worldwide trends in underweight and obesity from 1990 to 2022: a pooled analysis of 3663 population-representative studies with 222 million children, adolescents, and adults

NCD Risk Factor Collaboration (NCD-RisC): Ana Rito, Departamento de Alimentação e Nutrição, INSA

Background: Underweight and obesity are associated with adverse health outcomes throughout the life course. We estimated the individual and combined prevalence of underweight or thinness and obesity, and their changes, from 1990 to 2022 for adults and school-aged children and adolescents in 200 countries and territories. Methods: We used data from 3663 population-based studies with 222 million participants that measured height and weight in representative samples of the general population. We used a Bayesian hierarchical model to estimate trends in the prevalence of different BMI categories, separately for adults (age ≥20 years) and school-aged children and adolescents (age 5-19 years), from 1990 to 2022 for 200 countries and territories. For adults, we report the individual and combined prevalence of underweight (BMI <18·5 kg/m2) and obesity (BMI ≥30 kg/m2). For school-aged children and adolescents, we report thinness (BMI <2 SD below the median of the WHO growth reference) and obesity (BMI >2 SD above the median). Findings: From 1990 to 2022, the combined prevalence of underweight and obesity in adults decreased in 11 countries (6%) for women and 17 (9%) for men with a posterior probability of at least 0·80 that the observed changes were true decreases. The combined prevalence increased in 162 countries (81%) for women and 140 countries (70%) for men with a posterior probability of at least 0·80. In 2022, the combined prevalence of underweight and obesity was highest in island nations in the Caribbean and Polynesia and Micronesia, and countries in the Middle East and north Africa. Obesity prevalence was higher than underweight with posterior probability of at least 0·80 in 177 countries (89%) for women and 145 (73%) for men in 2022, whereas the converse was true in 16 countries (8%) for women, and 39 (20%) for men. From 1990 to 2022, the combined prevalence of thinness and obesity decreased among girls in five countries (3%) and among boys in 15 countries (8%) with a posterior probability of at least 0·80, and increased among girls in 140 countries (70%) and boys in 137 countries (69%) with a posterior probability of at least 0·80. The countries with highest combined prevalence of thinness and obesity in school-aged children and adolescents in 2022 were in Polynesia and Micronesia and the Caribbean for both sexes, and Chile and Qatar for boys. Combined prevalence was also high in some countries in south Asia, such as India and Pakistan, where thinness remained prevalent despite having declined. In 2022, obesity in school-aged children and adolescents was more prevalent than thinness with a posterior probability of at least 0·80 among girls in 133 countries (67%) and boys in 125 countries (63%), whereas the converse was true in 35 countries (18%) and 42 countries (21%), respectively. In almost all countries for both adults and school-aged children and adolescents, the increases in double burden were driven by increases in obesity, and decreases in double burden by declining underweight or thinness. Interpretation: The combined burden of underweight and obesity has increased in most countries, driven by an increase in obesity, while underweight and thinness remain prevalent in south Asia and parts of Africa. A healthy nutrition transition that enhances access to nutritious foods is needed to address the remaining burden of underweight while curbing and reversing the increase in obesity.

Research in context - Evidence before this study: We searched MEDLINE (via PubMed) for articles published from database inception up to Sept 25, 2023, with no language restrictions, using the following search terms: (((“obesity”[mh:noexp] OR “overweight”[mh:noexp] OR “overnutrition”[mh:noexp]) AND (“thinness”[mh:noexp] OR “malnutrition”[mh:noexp])) OR (“double burden” AND “malnutrition”)) AND (“Health Surveys”[mh] OR “Epidemiological Monitoring”[mh] OR “Prevalence”[mh]) AND (“global*” OR “worldwide”) NOT “patient*”[Title] NOT Comment[ptyp] NOT Case Reports[ptyp]. Articles were screened to include measured data on height and weight, collected from probabilistic samples of national, subnational, or community populations aged 5 years and older. We found two studies that reported the prevalence of underweight and obesity in adults, one of which also reported the prevalence of thinness and obesity in school-aged children and adolescents, for all countries in the world. These outcomes were reported separately, and neither their combination nor their relative sizes were evaluated. The most recent data for both age groups were from 2016. We found eight studies on the double burden of malnutrition in low-income and middle-income countries, using data mostly from Demographic and Health Surveys or Global School-based Student Health Surveys. These studies covered only women of reproductive age or school-aged children and adolescents, and few assessed change over time. We found two other studies that covered multiple world regions but they did not report country-level prevalence or assess change over time. These studies defined double burden of malnutrition at the level of the individual (eg, combination of stunting and obesity), household (eg, presence of underweight and obesity in different members of the same household), or country, depending on the study. None reported for all countries in the world. - Added value of this study: - This study uses thousands of high-quality population-based studies, and presents consistent and up-to-date estimates of underweight, thinness, and obesity from late childhood through to adulthood, separately and in combination, for all countries in the world. It also analyses how the two components have contributed to the change in their combined burden over a period of more than three decades, 1990–2022, during which major changes occurred in food policies and programmes and nutrition. - Implications of all the available evidence: The combined prevalence of underweight and obesity has increased in most countries since 1990, due to the rise in obesity surpassing the decline in underweight. Exceptions were most countries in south Asia, and some in southeast Asia and sub-Saharan Africa, where a decrease in the prevalence of underweight led to a decrease in the combined burden. This transition to obesity dominance was already apparent in adults in 1990 in much of the world, and has followed in school-aged children and adolescents. There is a need throughout the world for social and agricultural policies and food programmes that address the remaining burden of underweight while curbing and reversing the rise in obesity by enhancing access to healthy and nutritious foods.

This study was funded by the UK Medical Research Council (grant number MR/V034057/1), the UK Research and Innovation (Research England Policy Support Fund), UK Research and Innovation (Innovate UK grant number 10103595, for participation in the OBCT consortium funded by the European Union grant agreement 101080250), and European Union (STOP Project grant agreement 774548). BZ is supported by a fellowship from the Abdul Latif Jameel Institute for Disease and Emergency Analytics at Imperial College London, funded by a donation from Community Jameel.