Summary
Background Underweight and severe and morbid obesity are associated with highly elevated risks of adverse health
outcomes. We estimated trends in mean body-mass index (BMI), which characterises its population distribution, and
in the prevalences of a complete set of BMI categories for adults in all countries.
Methods We analysed, with use of a consistent protocol, population-based studies that had measured height and
weight in adults aged 18 years and older. We applied a Bayesian hierarchical model to these data to estimate trends
from 1975 to 2014 in mean BMI and in the prevalences of BMI categories (<18·5 kg/m² [underweight], 18·5 kg/m² to
<20 kg/m², 20 kg/m² to <25 kg/m², 25 kg/m² to <30 kg/m², 30 kg/m² to <35 kg/m², 35 kg/m² to <40 kg/m², ≥40 kg/m²
[morbid obesity]), by sex in 200 countries and territories, organised in 21 regions. We calculated the posterior
probability of meeting the target of halting by 2025 the rise in obesity at its 2010 levels, if post-2000 trends continue.
Findings We used 1698 population-based data sources, with more than 19·2 million adult participants (9·9 million men
and 9·3 million women) in 186 of 200 countries for which estimates were made. Global age-standardised mean BMI
increased from 21·7 kg/m² (95% credible interval 21·3–22·1) in 1975 to 24·2 kg/m² (24·0–24·4) in 2014 in men, and
from 22·1 kg/m² (21·7–22·5) in 1975 to 24·4 kg/m² (24·2–24·6) in 2014 in women. Regional mean BMIs in 2014 for men
ranged from 21·4 kg/m² in central Africa and south Asia to 29·2 kg/m² (28·6–29·8) in Polynesia and Micronesia; for
women the range was from 21·8 kg/m² (21·4–22·3) in south Asia to 32·2 kg/m² (31·5–32·8) in Polynesia and Micronesia.
Over these four decades, age-standardised global prevalence of underweight decreased from 13·8% (10·5–17·4) to 8·8%
(7·4–10·3) in men and from 14·6% (11·6–17·9) to 9·7% (8·3–11·1) in women. South Asia had the highest prevalence of
underweight in 2014, 23·4% (17·8–29·2) in men and 24·0% (18·9–29·3) in women. Age-standardised prevalence of
obesity increased from 3·2% (2·4–4·1) in 1975 to 10·8% (9·7–12·0) in 2014 in men, and from 6·4% (5·1–7·8) to 14·9%
(13·6–16·1) in women. 2·3% (2·0–2·7) of the world’s men and 5·0% (4·4–5·6) of women were severely obese (ie, have
BMI ≥35 kg/m²). Globally, prevalence of morbid obesity was 0·64% (0·46–0·86) in men and 1·6% (1·3–1·9) in women.
Interpretation If post-2000 trends continue, the probability of meeting the global obesity target is virtually zero. Rather,
if these trends continue, by 2025, global obesity prevalence will reach 18% in men and surpass 21% in women; severe
obesity will surpass 6% in men and 9% in women. Nonetheless, underweight remains prevalent in the world’s poorest
regions, especially in south Asia.
