'Fat black sheep': Educational penalties of childhood obesity in an emerging country.

OBJECTIVE: This article explores the relationship between childhood obesity and educational outcomes in Mexico, a country where excess weight is predominant. DESIGN: Using complementary multivariate estimators, we empirically investigate the association between childhood excess weight, measured in 2002, and schooling attainment measured 10 years later. Non-linear specifications are tested, and heterogeneous effects according to gender, living area and economic backgrounds are investigated. SETTING: To fill the literature gap, this study focuses on the understudied context of emerging countries such as Mexico. PARTICIPANTS: Panel data from the Mexican Family Life Survey (2002-2012) are used. We restricted the sample to adolescent individuals who had between 9 and 15 years old in 2002 (attended primary or secondary school in 2002). The survey provides an accurate follow-up information on weight, height and waist circumference for each individual. RESULTS: Controlling for a comprehensive set of covariates, we find that the relationship is non-linear in Mexico. While weight-based childhood obesity and abdominal adiposity are significantly associated with lower school attainment, at least in urban settings, no schooling gap is found between overweight students and their normal-weight counterparts. Along with rural-urban heterogeneity, obesity-based educational penalties appear to be stronger for girls and students from privileged economic backgrounds. CONCLUSIONS: These results emphasise the co-occurrence of anti-fat and pro-fat social norms in Mexican schools: while anti-fat norms may particularly concern female, richer and urban students, pro-fat norms might persist among male, poorer and rural students. These findings have important implications for public policy, namely about awareness anti-obesity programmes.

"Mother's milk": Is there a social reversal in breastfeeding practices along with economic development?

Previous studies suggest that macro- and micro-level factors jointly influence breastfeeding (BF) practices, but empirical evidence on the dynamics of such interactions along with the process of a country's economic development remains limited. Based on 42 Demographic Health Surveys (DHS) conducted in 15 Asian countries with a large time window (1990-2017), we thus test the existence of a reversal in the association between household wealth and BF practices throughout the development process. Four BF indicators (early initiation of BF, exclusive BF, continued BF at one year and two years) are examined, along with a standardized asset-based household wealth index allowing for cross-wave and cross-country comparisons. To highlight the dynamics of the wealth-BF association, we carry out econometric estimations, including interaction terms between household wealth and the country's level of economic development (low, medium, and high) or time. Instrumental variable estimations are also performed to limit suspected endogeneity issues. Our results confirm a transition in the wealth gradient of exclusive BF and continued BF in Asian countries. More precisely, while these practices are pro-poor in the poorest countries of the sample, they progressively spread to wealthier households along with the level of economic development. For exclusive BF, this transition has resulted in a reversal of the wealth gradient at the end of the period (i.e., exclusive BF prevalence among the rich overpassing that of the poor). We fail, however, to observe this kind of transition for early initiation of BF, this practice remaining pro-poor, whatever the level of economic development. To sum up, our results provide robust evidence of a transition in the wealth gradient of some BF practices along with economic development and time, and thus largely echo the literature exploring the social reversal hypothesis in the case of non-communicable diseases.

Locked nucleic acids (LNAs) reveal sequence requirements and kinetics of Xist RNA localization to the X chromosome.

A large fraction of the mammalian genome is transcribed into long noncoding RNAs. The RNAs remain largely uncharacterized as the field awaits new technologies to aid functional analysis. Here, we describe a unique use of locked nucleic acids (LNAs) for studying nuclear long noncoding RNA, an RNA subclass that has been less amenable to traditional knockdown techniques. We target LNAs at Xist RNA and show displacement from the X chromosome with fast kinetics. Xist transcript stability is not affected. By targeting different Xist regions, we identify a localization domain and show that polycomb repressive complex 2 (PRC2) is displaced together with Xist. Thus, PRC2 depends on RNA for both initial targeting to and stable association with chromatin. H3K27-trimethyl marks and gene silencing remain stable. Time-course analysis of RNA relocalization suggests that Xist and PRC2 bind to different regions of the X at the same time but do not reach saturating levels immediately. Thus, LNAs provide a tool for studying an emerging class of regulatory RNA and offer a window of opportunity to target epigenetic modifications with possible therapeutic applications.

Updating the association between socioeconomic status and obesity in low-income and lower-middle-income sub-Saharan African countries: A literature review.

Globally, the literature tends to emphasize negative associations between socioeconomic status (SES) and bodyweight in countries improving their economic development. However, little is known about the social distribution of obesity in sub-Saharan Africa (SSA) where economic growth has been highly heterogeneous the last decades. This paper reviews an exhaustive set of recent empirical studies examining its association in low-income and lower-middle-income countries in SSA. Although there is evidence of a positive association between SES and obesity in low-income countries, we found mixed associations in lower-middle-income countries, potentially providing evidence of a social reversal of the obesity burden.

School starting age and nutritional outcomes: Evidence from Brazil.

Recent studies reported that the age of primary school enrolment is a major driver of educational achievement and adult income, but its impacts on childhood health and nutrition remain largely unknown, particularly in developing countries where childhood stunting and overweight coexist. In Brazil, children are supposed to enrol in primary school the year they turn 6. Using a database of middle school students in Brazil based on a 2015 survey, I implemented an instrumental variables strategy using quasi-exogenous variations in the students' birthdates to isolate the impact of late primary school enrolment (i.e., older than 6 when enrolled) on height-for-age and body mass-for-age indicators. Overall, late enrolment has protective effects against hazardous weight gain (-0.14 z-score unit) but significantly increases the risk of moderate stunting (by 1.5% points). Heterogeneity in family backgrounds may explain these results. Indeed, delayed school enrolment is particularly detrimental for the nutritional status of students from underprivileged settings. In terms of public policy, rather than changing school starting age, this study highlights the importance of focusing on pathways to fight both stunting and overweight conditions in Brazilian children.

Does inequality have a silver lining? Municipal income inequality and obesity in Mexico.

Income inequality and obesity are both widespread socioeconomic issues, particularly salient in middle-income countries. This article seeks to detect the relationship between local income inequality and excess weight in Mexico, using robust municipal income inequality measures generated through small area estimation method and instrumental variable multilevel estimations. Our results emphasize a negative impact of municipal income inequality on individual bodyweight, especially for women. We also explore the potential channels through which income inequality may decrease bodyweight. Three-stage least squares estimations highlight that the social capital pathway, the public policy pathway and the psychological pathway help to explain the negative effect of inequality on excess weight. Our results are fairly robust to alternative inequality measures and nutritional indicators.

Causal effects of socioeconomic status on central adiposity risks: Evidence using panel data from urban Mexico.

Associated with overweight, obesity and chronic diseases, the nutrition transition process reveals important socioeconomic issues in Mexico. Using panel data from the Mexican Family Life Survey, the purpose of the study is to estimate the causal effect of household socioeconomic status (SES) on nutritional outcomes among urban adults. We divide the analysis into two steps. First, using a mixed clustering procedure, we distinguish four socioeconomic classes based on income, educational and occupational dimensions: (i) a poor class; (ii) a lower-middle class; (iii) an upper-middle class; (iv) a rich class. Second, using an econometric framework adapted to our study (the Hausman-Taylor estimator), we measure the impact of belonging to these socioeconomic groups on individual anthropometric indicators, based on the body-mass index (BMI) and the waist-to-height ratio (WHtR). Our results make several contributions: (i) we show that a new middle class, rising out of poverty, is the most exposed to the risks of adiposity; (ii) as individuals from the upper class seem to be fatter than individuals from the upper-middle class, we can reject the assumption of an inverted U-shaped relationship between socioeconomic and anthropometric status as commonly suggested in emerging economies; (iii) the influence of SES on central adiposity appears to be particularly strong for men.