| Abstract [eng] |
The prevalence of overweight and obesity has increased globally over the recent decades, yet most studies rely exclusively on body mass index, which does not capture changes in body fat distribution or overall body composition. The aim of this literature review was to analyse and summarise global secular changes in adult body size and shape, body proportions, and body composition, their association with health outcomes, and contributing factors to observed changes. In addition, methodological limitations of the existing evidence base were assessed. A combined methodological approach was used. A systematic literature search was conducted in PubMed and Google Scholar according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines, supplemented by backward citation tracking, to identify evidence on body size, body shape, and body composition. Studies reporting population-level anthropometric trends or associations between anthropometric indicators and health outcomes in adults were qualified for inclusion. At this stage, a total of 32 studies were included for qualitative synthesis. Eight supervisor-recommended references on secular trends in adult height and body proportions were integrated as contextual evidence, documented separately in Annex 2. Adult body mass index and obesity prevalence have increased consistently across almost all populations over four decades, with the most rapid recent increases in low- and middle-income countries. A key finding is that waist circumference has increased disproportionately relative to body mass index across at least six countries on three continents, indicating a shift towards greater central adiposity. Central adiposity measures, particularly waist circumference and waist-to-height ratio, consistently outperformed body mass index in predicting cardiometabolic risk. The body mass index- mortality relationship was non-linear, with overweight associated with lower all-cause mortality and severe obesity showing significantly elevated risk. Secular trends in adult height, documented across more than 200 countries, however, it has been much less pronounced over the past few decades than concurrent increases in body mass index and waist circumference, and have occurred predominantly through gains in leg length. This indicates that the anthropometric transformation of recent decades is primarily a shift in body mass and body shape rather than body height acceleration in the traditional sense. Relative leg length emerged as an independent marker of early-life conditions and cardiometabolic risk. Contributing factors include the nutrition transition, urbanisation, declining physical activity, and population-specific biological variation. The analysed studies show significant geographical variations, however, mostly only body mass index is considered. The global obesity epidemic is changing, with central adiposity increasing beyond what body mass index trends suggest. Incorporating waist circumference and complementary anthropometric indicators into surveillance and clinical practice is essential to more accurately capture the course of population-level metabolic risk. Future research should prioritise large-scale longitudinal studies using multiple anthropometric indicators, invest in surveillance in underrepresented regions, and standardise waist circumference measurement protocols to enable reliable global comparisons. |
