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

A list of authors and their affiliations appears online. A supplementary appendix is herewith attached.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 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.peer-reviewe

Investigation on the characteristics of micro/nanofiber Bragg grating for refractive index sensing

Using the fiber Bragg grating equation and the functional relation of the fundamental effective mode refractive index (RI), the mathematical model of the wavelength shift and the relational function of wavelength sensitivity are established, when the reflected wavelength of the micro/nanofiber Bragg grating (MNFBG) changes with ambient RI and the fiber radius. The theoretical relationship demonstrates that the variation of MNFBG reflected wavelengths is dependent on the change of effective RI with fiber radius and ambient RI. Meanwhile, we also study the variation of effective RI and its sensitivity in detail. The results show that the effective RI nonlinearly decreases with fiber-core radius and ambient refractive index decreasing, and its sensitivity increases as the ambient refractive index increases, and the sensitivity, linearity and the linear response range increase with the decrease of the fiber radius. For a fiber radius of 0.5 μm, by simulating the curves of the effective index versus ambient RI in the index ranges of 1.20-1.30 and 1.33-1.43 respectively, the values of wavelength sensitivity of 477.33 nm/RIU and 856.30 nm/RIU and the values of high linearity of 99.2% and 99.7% are obtained, which not only verifies the analysis conclusions and the measurement program for RI sensing with MNFBG, but also supplies references for the RI sensor design, optimization and the application.</jats:p

A STUDY OF NITROGEN ISOELECTRONIC TRAPS IN GaAs

The photoluminescences of nitrogen implanted GaAs samples at 77 K have been studied under high pressures. The luminescence peaks of excitons Nx bound to N trap central cell potential and excitons NT bound to deformation potential were observed. The exprimen-tal value of pressure coefficient of Nx level is 2.8 meV/kbar. Under the atmospheric pressure, the N resonant state is at 179 meV above the conduction band edge. The pressure behaviors of electron-phonon coupling strength of N isoelectronic trap and effective radius of bound exciton are discussed.</jats:p