Worldwide trends in children’s and adolescents’ body mass index, underweight, overweight and obesity, in comparison with adults, from 1975 to 2016: A pooled analysis of 2,416 population-based measurement studies with 128.9 million participants (Pre-published version)

Abstract

Background: Being underweight as well as overweight and obese in childhood and adolescence are associated with adverse health consequences throughout the life-course. Our aim was to estimate worldwide trends in mean body mass index (BMI) and a comprehensive set of BMI categories that cover the underweight to obese range in school-aged children and adolescents, and to compare trends with those of adults. Methods: We re-analysed and pooled 2,416 population-based studies with measurements of height and weight on 128.9 million participants aged five years and older, including 31.5 million aged 5-19 years. We used a Bayesian hierarchical model to estimate trends from 1975 to 2016 for 200 countries in mean BMI and in prevalence of BMI in the following categories for children and adolescents aged 5-19 years: <-2SD from the median of the WHO growth reference (referred to as moderate and severe underweight hereafter), -2SD to <-1SD (mild underweight), -1SD to 1SD (normal weight), >1 SD to 2SD (overweight), and >2SD (obesity). Findings: Regional change in age-standardised mean BMI in girls ranged from -0.01 kg/m2 per decade (-0.42 to 0.39; PP of the observed decrease being a true decrease = 0.5098) in eastern Europe to 1.00 kg/m2 per decade (0.69-1.35; PP > 0.9999) in central Latin America and 0.95 kg/m2 per decade (0.64-1.25; PP > 0.9999) in Polynesia and Micronesia. The range for boys was from 0.09 kg/m2 per decade (-0.33 to 0.49; PP = 0.6926) in eastern Europe to 0.77 kg/m2 per decade (0.50-1.06 PP > 0.9999) in Polynesia and Micronesia. There has been a recent flattening of trends in northwestern Europe and the high-income English-speaking and Asia-Pacific regions for both sexes, southwestern Europe for boys, and central and Andean Latin America for girls. In contrast, the rise in BMI has accelerated in east and south Asia for both sexes, and southeast Asia for boys. Global age-standardised prevalence of obesity increased from 0.7% (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; the prevalence of 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. Prevalence of moderate and severe underweight was highest in India, 22.7% (16.7-29.6) among girls and 30.7% (23.5- 38.0) among boys. Prevalence of obesity was >30% in girls in Nauru, the Cook Islands and Palau and boys in the Cook Islands, Nauru, Palau, Niue and American Samoa in 2016, and was also ~20% or more in several countries in Polynesia and Micronesia, the Middle East and north Africa, and the Caribbean as well as in the USA. The global number of moderately or severely underweight girls and boys was 75 million (44-117) and 117 million (70-178), respectively, in 2016; The number of obese girls and boys was 50 (24-89) and 74 (39-125) million, respectively. Interpretation: The rise in children’s and adolescents’ BMI has plateaued in many highincome countries, albeit at high levels, but has accelerated in parts of Asia, with trends no longer correlated with those of adults. Funding: Wellcome Trust; AstraZeneca Young Health Programme.