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[This corrects the article DOI: 10.1371/journal.pone.0217821.].

Background In recent decades, the prevalence of obesity in children has increased dramatically. This worldwide epidemic has important consequences, including psychiatric, psychological and psychosocial disorders in childhood and increased risk of developing non-communicable diseases (NCDs) later in life. Treatment of obesity is difficult and children with excess weight are likely to become adults with obesity. These trends have led member states of the World Health Organization (WHO) to endorse a target of no increase in obesity in childhood by 2025. Main body Estimates of overweight in children aged under 5 years are available jointly from the United Nations Children’s Fund (UNICEF), WHO and the World Bank. The Institute for Health Metrics and Evaluation (IHME) has published country-level estimates of obesity in children aged 2–4 years. For children aged 5–19 years, obesity estimates are available from the NCD Risk Factor Collaboration. The global prevalence of overweight in children aged 5 years or under has increased modestly, but with heterogeneous trends in low and middle-income regions, while the prevalence of obesity in children aged 2–4 years has increased moderately. In 1975, obesity in children aged 5–19 years was relatively rare, but was much more common in 2016. Conclusions It is recognised that the key drivers of this epidemic form an obesogenic environment, which includes changing food systems and reduced physical activity. Although cost-effective interventions such as WHO ‘best buys’ have been identified, political will and implementation have so far been limited. There is therefore a need to implement effective programmes and policies in multiple sectors to address overnutrition, undernutrition, mobility and physical activity. To be successful, the obesity epidemic must be a political priority, with these issues addressed both locally and globally. Work by governments, civil society, private corporations and other key stakeholders must be coordinated.

•Child malnutrition is a major public health problem.•Globally in 2020, 149 million children <5 y of age were estimated to be stunted (too short for age) and 45 million were wasted (too thin for height).•The most consistent factors associated with child malnutrition are maternal education, household income, and maternal nutritional status. Child undernutrition is a major public health problem. Globally in 2020, 149 million children <5 y of age were estimated to be stunted (too short for age), 45 million to be wasted (too thin for height), and 38.9 million were overweight. The aim of this review was to examine previous studies to determine the factors associated with malnutrition and contribute to the existing body of evidence needed for the formulation of effective interventions. This systematic review was conducted using the 2020 Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. The Google Scholar database was used to search the studies conducted between 2012 and 2021. The included studies were searched by using some combinations of keywords and saved in Mendeley Desktop for review and referencing. Of 2150 articles retrieved from the Google Scholar databases, 37 met our inclusion criteria. Of the 37 studies reviewed; 13 were conducted in India, 5 in Ethiopia, 3 in Bangladesh, 2 in Ghana, 2 in Nepal, 2 in developing countries, and 1 each in Bolira, Benin, Netherland, Columbia, Pakistan, Malaysia, Africa, Egypt, Ecuadorian, and Indonesia. The most consistent factors associated with child malnutrition were maternal education, household income, maternal nutritional status, age of the child, availability of sanitation facility at home, size of family, birth order in the family, and child's birth weight. Breastfeeding and caring practices, cooking area and the fuel used, sex, and socioeconomic status of the children also contribute toward child malnutrition.

Background Three large new trials of unprecedented scale and cost, which included novel factorial designs, have found no effect of basic water, sanitation and hygiene (WASH) interventions on childhood stunting, and only mixed effects on childhood diarrhea. Arriving at the inception of the United Nations’ Sustainable Development Goals, and the bold new target of safely managed water, sanitation and hygiene for all by 2030, these results warrant the attention of researchers, policy-makers and practitioners. Main body Here we report the conclusions of an expert meeting convened by the World Health Organization and the Bill and Melinda Gates Foundation to discuss these findings, and present five key consensus messages as a basis for wider discussion and debate in the WASH and nutrition sectors. We judge these trials to have high internal validity, constituting good evidence that these specific interventions had no effect on childhood linear growth, and mixed effects on childhood diarrhea. These results suggest that, in settings such as these, more comprehensive or ambitious WASH interventions may be needed to achieve a major impact on child health. Conclusion These results are important because such basic interventions are often deployed in low-income rural settings with the expectation of improving child health, although this is rarely the sole justification. Our view is that these three new trials do not show that WASH in general cannot influence child linear growth, but they do demonstrate that these specific interventions had no influence in settings where stunting remains an important public health challenge. We support a call for transformative WASH, in so much as it encapsulates the guiding principle that – in any context – a comprehensive package of WASH interventions is needed that is tailored to address the local exposure landscape and enteric disease burden.

Background Until recently, undernourished children were usually assessed using simple anthropometric measurements, which provide global assessments of nutritional status. There is increasing interest in obtaining more direct data on body composition to assess the effects of undernutrition on fat-free mass (FFM) and its constituents, such as muscle and organs, and on fat mass (FM) and its regional distribution. Main text Recent studies show that severe-acute undernutrition, categorised as ‘wasting’, is associated with major deficits in both FFM and FM that may persist in the long-term. Fat distribution appears more central, but this is more associated with the loss of peripheral fat than with the elevation of central fat. Chronic undernutrition, categorised as ‘stunting’, is associated with deficits in FFM and in specific components, such as organ size. However, the magnitude of these deficits is reduced, or – in some cases – disappears, after adjustment for height. This suggests that FFM is largely reduced in proportion to linear growth. Stunted children vary in their FM – in some cases remaining thin throughout childhood, but in other cases developing higher levels of FM. The causes of this heterogeneity remain unclear. Several different pathways may underlie longitudinal associations between early stunting and later body composition. Importantly, recent studies suggest that short children are not at risk of excess fat deposition in the short term when given nutritional supplementation. Conclusion The short- and long-term functional significance of FFM and FM for survival, physical capacity and non-communicable disease risk means that both tissues merit further attention in research on child undernutrition.

Child undernutrition is a global public health problem with serious implications. In this study, we estimate predictive algorithms for the determinants of childhood stunting by using various machine learning (ML) algorithms. This study draws on data from the Ethiopian Demographic and Health Survey of 2016. Five ML algorithms including eXtreme gradient boosting, k-nearest neighbours (k-NN), random forest, neural network and the generalised linear models were considered to predict the socio-demographic risk factors for undernutrition in Ethiopia. Households in Ethiopia. A total of 9471 children below 5 years of age participated in this study. The descriptive results show substantial regional variations in child stunting, wasting and underweight in Ethiopia. Also, among the five ML algorithms, xgbTree algorithm shows a better prediction ability than the generalised linear mixed algorithm. The best predicting algorithm (xgbTree) shows diverse important predictors of undernutrition across the three outcomes which include time to water source, anaemia history, child age greater than 30 months, small birth size and maternal underweight, among others. The xgbTree algorithm was a reasonably superior ML algorithm for predicting childhood undernutrition in Ethiopia compared to other ML algorithms considered in this study. The findings support improvement in access to water supply, food security and fertility regulation, among others, in the quest to considerably improve childhood nutrition in Ethiopia.

Undernutrition among children under the age of five years is a prevalent global issue, especially in Bangladesh. This study aimed to explore the relationships of household environmental conditions (HECs) with child undernutrition in Bangladesh, with a specific focus on rural-urban variations. We analysed children's data from the 2017/18 Bangladesh Demographic Health Survey. The outcome variable considered were measures of child undernutrition, including stunting, wasting and underweight. The primary exposure variables considered were indicators of HEC. We used a hierarchical multilevel mixed-effect generalized linear models (GLM) modified with a Poisson regression to explore the association between outcomes and exposures, adjusting for potential confounders. Nationally representative cross-sectional survey. 8,057 under-5 children. The prevalence of stunting, wasting and underweight in Bangladesh was 31%, 8%, and 22%, respectively, with notable urban-rural variations. Under-5 children who lived in houses constructed with unimproved materials (aRR: 1·17), exposed to household air pollution (aPR: 1·37), had unimproved drinking water sources (aPR: 1·28) or had poor handwashing facilities (aPR: 1·24) had a greater likelihood of stunting compared to their counterparts. Similar associations were observed for underweight. The likelihood of stunting and underweight increased with increasing scores of poor HECs, with variations in the effect size across urban-rural areas. The high prevalence of stunting and underweight in Bangladesh is linked to poor HECs, therefore, integrated approaches should be adopted to address these environmental factors collectively. Policies and programmes should prioritse enhancing housing quality to achieve sustainable improvements in child nutritional outcomes.

Undernutrition in children is a pressing global health problem, manifested in part by impaired linear growth (stunting). Current nutritional interventions have been largely ineffective in over-coming stunting, emphasizing the need to obtain better understanding of its underlying causes. Treating Bangladeshi children with severe acute malnutrition with therapeutic foods reduced plasma levels of a biomarker of osteoclastic activity without affecting biomarkers of osteoblastic activity or improving their severe stunting. To characterize interactions among the gut microbiota, human milk oligosaccharides (HMOs), and osteoclast and osteoblast biology, young germ-free mice were colonized with cultured bacterial strains from a 6-mo-old stunted infant and fed a diet mimicking that consumed by the donor population. Adding purified bovine sialylated milk oligosaccharides (S-BMO) with structures similar to those in human milk to this diet increased femoral trabecular bone volume and cortical thickness, reduced osteoclasts and their bone marrow progenitors, and altered regulators of osteoclastogenesis and mediators of Th2 responses. Comparisons of germ-free and colonized mice revealed S-BMO-dependent and microbiota-dependent increases in cecal levels of succinate, increased numbers of small intestinal tuft cells, and evidence for activation of a succinate-induced tuft cell signaling pathway linked to Th2 immune responses. A prominent fucosylated HMO, 2′-fucosyllactose, failed to elicit these changes in bone biology, highlighting the structural specificity of the S-BMO effects. These results underscore the need to further characterize the balance between, and determinants of, osteoclastic and osteoblastic activity in stunted infants/children, and suggest that certain milk oligosaccharides may have therapeutic utility in this setting.

The double burden of malnutrition (DBM), defined as the simultaneous manifestation of both undernutrition and overweight and obesity, affects most low-income and middle-income countries (LMICs). This Series paper describes the dynamics of the DBM in LMICs and how it differs by socioeconomic level. This Series paper shows that the DBM has increased in the poorest LMICs, mainly due to overweight and obesity increases. Indonesia is the largest country with a severe DBM, but many other Asian and sub-Saharan African countries also face this problem. We also discuss that overweight increases are mainly due to very rapid changes in the food system, particularly the availability of cheap ultra-processed food and beverages in LMICs, and major reductions in physical activity at work, transportation, home, and even leisure due to introductions of activity-saving technologies. Understanding that the lowest income LMICs face severe levels of the DBM and that the major direct cause is rapid increases in overweight allows identifying selected crucial drivers and possible options for addressing the DBM at all levels.