Worldwide trends in body-mass index, underweight, overweight, and obesity from 1975 to 2016: a pooled analysis of 2416 population-based measurement studies in 128·9 million children, adolescents, and adults.
Level 3 - non-randomized controlled study
Bayesian hierarchical pooled analysis of observational population-based measurement studies across 200 countries.
PubMed 29029897 · doi:10.1016/S0140-6736(17)32129-3
What was done
Researchers pooled 2416 population-based studies comprising height and weight measurements from 128.9 million individuals aged 5 years and older, including 31.5 million youth aged 5 to 19 years, across 200 countries. Using a Bayesian hierarchical model, they estimated trends from 1975 to 2016 in mean BMI and prevalence across WHO-defined BMI categories (moderate and severe underweight, mild underweight, healthy weight, overweight, and obesity) in children and adolescents aged 5 to 19 years, comparing these trends with adult patterns.
What was found
Global age-standardised obesity prevalence increased from 0.7% (95% credible interval 0.4-1.2) in 1975 to 5.6% (4.8-6.5) in 2016 in girls, and from 0.9% (0.5-1.3) to 7.8% (6.7-9.1) in boys. In 2016, 50 million girls (24-89 million) and 74 million boys (39-125 million) were obese worldwide. Moderate and severe underweight decreased from 9.2% (6.0-12.9) to 8.4% (6.8-10.1) in girls and from 14.8% (10.4-19.5) to 12.4% (10.3-14.5) in boys, representing 75 million girls and 117 million boys in 2016. Underweight was highest in India (22.7% in girls, 30.7% in boys). Obesity prevalence exceeded 30% in several Pacific island nations and reached 20% or more in parts of the Middle East, North Africa, the Caribbean, and the USA. Mean BMI increases plateaued in high-income regions but accelerated in East, South, and Southeast Asia.
Why it matters
This study provides the largest global accounting of youth BMI changes over four decades, showing a rapid transition toward childhood obesity globally alongside persistent, unresolved undernutrition in parts of Asia.
Limits
The study relies on statistical imputation for regions and historical periods with sparse primary survey data. BMI was the sole metric and does not differentiate fat mass from lean tissue or skeletal maturation. The abstract does not report health outcomes, socioeconomic inequalities within countries, or behavioral drivers.
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