Did child obesity decline after 2016 food regulations in Chile? / ¿Disminuyó la obesidad infantil en Chile después de la introducción de las regulaciones alimentarias en el 2016? / A obesidade infantil diminuiu após a regulamentação de alimentos de 2016 no Chile?

[ABSTRACT]. We estimated trends in the prevalence of obesity and overweight among Chilean primary and secondary students before and after Chile’s 2016 regulations on the marketing and availability of foods high in energy, total sugars, sodium, or saturated fat. We used data from Chile’s Survey of Nutrition, which measured the body mass index (BMI) of students in government-funded schools. Using BMI thresholds defined by the World Health Organization, we calculated the prevalence of overweight and obesity for each year from 2013 to 2019 among students attending pre-kindergarten (age 4 years), kindergarten (age 5 years), first grade (6 years), and ninth grade (14 years). In ninth grade students, overweight and obesity prevalence rose by 2 percentage points over the 3 years after introduction of the 2016 regulations. In pre-kindergarten, kindergarten, and first grade, overweight and obesity fell 1 to 3 percentage points 1 year after the regulations were introduced, but rebounded to previous levels the next year. Chile’s food regulations were not followed by a sustained decline in obesity in primary- and secondary-school students. Future research should examine whether and how children in Chile and other countries maintain high levels of overweight and obesity despite food regulations designed to reduce consumption of obesogenic foods and beverages.

[RESUMEN]. Se estimaron las tendencias en la prevalencia de la obesidad y el sobrepeso en estudiantes chilenos de educación primaria y secundaria, antes y después de las regulaciones introducidas en Chile en el 2016 sobre la comercialización y disponibilidad de productos hipercalóricos, con un alto contenido de azúcares, sodio o grasas saturadas. Se utilizaron datos del Mapa Nutricional de Chile, una encuesta en la que se midió el índice de masa corporal (IMC) de la población estudiantil de las escuelas públicas. Tomando los umbrales de IMC definidos por la Organización Mundial de la Salud, se calculó la prevalencia del sobrepeso y la obesidad para cada año entre el 2013 y el 2019 en estudiantes de jardín de infancia (4 años), preescolar (5 años), primer grado (6 años) y noveno grado (14 años). En los estudiantes de noveno grado, la prevalencia del sobrepeso y la obesidad aumentó en 2 puntos porcentuales durante los 3 años posteriores a la introducción de las regulaciones del 2016. En el caso de los grupos de jardín de infancia, preescolar y primer grado, el sobrepeso y la obesidad disminuyeron entre 1 y 3 puntos porcentuales un año después de la introducción de las regulaciones, pero al año siguiente volvieron a los niveles anteriores. La introducción de las regulaciones alimentarias de Chile no estuvo seguida de una disminución continua de la obesidad en la población estudiantil de primaria y secundaria. En las investigaciones futuras se deberá examinar si la población infantil de Chile y otros países mantiene niveles altos de sobrepeso y obesidad a pesar de las regulaciones alimentarias diseñadas para reducir el consumo de productos y bebidas obesogénicos, así como las características específicas que adopta este problema de salud.

[RESUMO]. Foram estimadas tendências de prevalência da obesidade e do sobrepeso em alunos chilenos do ensino fundamental e médio antes e depois da regulamentação de 2016 da propaganda e disponibilidade de alimentos com alto teor calórico ou ricos em açúcares totais, sódio ou gorduras saturadas no Chile. Foram utilizados dados obtidos da Pesquisa em Nutrição do Chile, que aferiu o índice de massa corporal (IMC) de escolares da rede pública. Com base nos limiares de IMC definidos pela Organização Mundial da Saúde (OMS), calculou-se a prevalência anual de sobrepeso e obesidade em crianças na pré-escola (4 anos), no jardim da infância (5 anos), no primeiro ano (6 anos) e no nono ano (14 anos) em cada ano no período entre 2013 e 2019. Entre os alunos do nono ano, a prevalência de sobrepeso e obesidade aumentou 2 pontos percentuais nos 3 anos que se seguiram à introdução da regulamentação de 2016. Entre os alunos da pré-escola, do jardim de infância e do primeiro ano, ocorreu uma redução de 1 a 3 pontos percentuais na prevalência de sobrepeso e obesidade um ano após a introdução da regulamentação, mas os níveis voltaram a subir no ano seguinte. A regulamentação de alimentos não resultou em um declínio sustentado da obesidade nos alunos do ensino fundamental e médio do Chile. Pesquisas futuras devem ser realizadas para avaliar se, e como, a prevalência de sobrepeso e obesidade nas crianças chilenas e de outros países se mantém alta a despeito da regulamentação de alimentos visando à redução do consumo de alimentos e bebidas obesogênicos.

Did child obesity decline after 2016 food regulations in Chile?

We estimated trends in the prevalence of obesity and overweight among Chilean primary and secondary students before and after Chile's 2016 regulations on the marketing and availability of foods high in energy, total sugars, sodium, or saturated fat. We used data from Chile's Survey of Nutrition, which measured the body mass index (BMI) of students in government-funded schools. Using BMI thresholds defined by the World Health Organization, we calculated the prevalence of overweight and obesity for each year from 2013 to 2019 among students attending pre-kindergarten (age 4 years), kindergarten (age 5 years), first grade (6 years), and ninth grade (14 years). In ninth grade students, overweight and obesity prevalence rose by 2 percentage points over the 3 years after introduction of the 2016 regulations. In pre-kindergarten, kindergarten, and first grade, overweight and obesity fell 1 to 3 percentage points 1 year after the regulations were introduced, but rebounded to previous levels the next year. Chile's food regulations were not followed by a sustained decline in obesity in primary- and secondary-school students. Future research should examine whether and how children in Chile and other countries maintain high levels of overweight and obesity despite food regulations designed to reduce consumption of obesogenic foods and beverages.

Se estimaron las tendencias en la prevalencia de la obesidad y el sobrepeso en estudiantes chilenos de educación primaria y secundaria, antes y después de las regulaciones introducidas en Chile en el 2016 sobre la comercialización y disponibilidad de productos hipercalóricos, con un alto contenido de azúcares, sodio o grasas saturadas. Se utilizaron datos del Mapa Nutricional de Chile, una encuesta en la que se midió el índice de masa corporal (IMC) de la población estudiantil de las escuelas públicas. Tomando los umbrales de IMC definidos por la Organización Mundial de la Salud, se calculó la prevalencia del sobrepeso y la obesidad para cada año entre el 2013 y el 2019 en estudiantes de jardín de infancia (4 años), preescolar (5 años), primer grado (6 años) y noveno grado (14 años). En los estudiantes de noveno grado, la prevalencia del sobrepeso y la obesidad aumentó en 2 puntos porcentuales durante los 3 años posteriores a la introducción de las regulaciones del 2016. En el caso de los grupos de jardín de infancia, preescolar y primer grado, el sobrepeso y la obesidad disminuyeron entre 1 y 3 puntos porcentuales un año después de la introducción de las regulaciones, pero al año siguiente volvieron a los niveles anteriores. La introducción de las regulaciones alimentarias de Chile no estuvo seguida de una disminución continua de la obesidad en la población estudiantil de primaria y secundaria. En las investigaciones futuras se deberá examinar si la población infantil de Chile y otros países mantiene niveles altos de sobrepeso y obesidad a pesar de las regulaciones alimentarias diseñadas para reducir el consumo de productos y bebidas obesogénicos, así como las características específicas que adopta este problema de salud.

Foram estimadas tendências de prevalência da obesidade e do sobrepeso em alunos chilenos do ensino fundamental e médio antes e depois da regulamentação de 2016 da propaganda e disponibilidade de alimentos com alto teor calórico ou ricos em açúcares totais, sódio ou gorduras saturadas no Chile. Foram utilizados dados obtidos da Pesquisa em Nutrição do Chile, que aferiu o índice de massa corporal (IMC) de escolares da rede pública. Com base nos limiares de IMC definidos pela Organização Mundial da Saúde (OMS), calculou-se a prevalência anual de sobrepeso e obesidade em crianças na pré-escola (4 anos), no jardim da infância (5 anos), no primeiro ano (6 anos) e no nono ano (14 anos) em cada ano no período entre 2013 e 2019. Entre os alunos do nono ano, a prevalência de sobrepeso e obesidade aumentou 2 pontos percentuais nos 3 anos que se seguiram à introdução da regulamentação de 2016. Entre os alunos da pré-escola, do jardim de infância e do primeiro ano, ocorreu uma redução de 1 a 3 pontos percentuais na prevalência de sobrepeso e obesidade um ano após a introdução da regulamentação, mas os níveis voltaram a subir no ano seguinte. A regulamentação de alimentos não resultou em um declínio sustentado da obesidade nos alunos do ensino fundamental e médio do Chile. Pesquisas futuras devem ser realizadas para avaliar se, e como, a prevalência de sobrepeso e obesidade nas crianças chilenas e de outros países se mantém alta a despeito da regulamentação de alimentos visando à redução do consumo de alimentos e bebidas obesogênicos.

The effect of smaller classes on infection-related school absence: evidence from the Project STAR randomized controlled trial.

BACKGROUND: In an effort to reduce viral transmission, many schools reduced class sizes during the recent pandemic. Yet the effect of class size on transmission is unknown. METHODS: We used data from Project STAR, a randomized controlled trial in which 10,816 Tennessee elementary students were assigned at random to smaller classes (13 to 17 students) or larger classes (22 to 26 students) in 1985-89. We merged Project STAR schools with data on local deaths from pneumonia and influenza in the 122 Cities Mortality Report System. Using mixed effects linear, Poisson, and negative binomial regression, we estimated the main effect of smaller classes on absence. We used an interaction to test whether the effect of small classes on absence was larger when and where community pneumonia and influenza prevalence was high. RESULTS: Small classes reduced absence by 0.43 days/year (95% CI -0.06 to -0.80, p < 0.05), but small classes had no significant interaction with community pneumonia and influenza mortality (95% CI -0.27 to + 0.30, p > 0.90), indicating that the reduction in absence due to small classes was not larger when community disease prevalence was high. CONCLUSION: Small classes reduced absence, but the reduction was not larger when disease prevalence was high, so the reduction in absence was not necessarily achieved by reducing infection. Small classes, by themselves, may not suffice to reduce the spread of respiratory viruses.

Did child obesity decline after 2016 food regulations in Chile? / ¿Disminuyó la obesidad infantil en Chile después de la introducción de las regulaciones alimentarias en el 2016? / A obesidade infantil diminuiu após a regulamentação de alimentos de 2016 no Chile?

ABSTRACT We estimated trends in the prevalence of obesity and overweight among Chilean primary and secondary students before and after Chile's 2016 regulations on the marketing and availability of foods high in energy, total sugars, sodium, or saturated fat. We used data from Chile's Survey of Nutrition, which measured the body mass index (BMI) of students in government-funded schools. Using BMI thresholds defined by the World Health Organization, we calculated the prevalence of overweight and obesity for each year from 2013 to 2019 among students attending pre-kindergarten (age 4 years), kindergarten (age 5 years), first grade (6 years), and ninth grade (14 years). In ninth grade students, overweight and obesity prevalence rose by 2 percentage points over the 3 years after introduction of the 2016 regulations. In pre-kindergarten, kindergarten, and first grade, overweight and obesity fell 1 to 3 percentage points 1 year after the regulations were introduced, but rebounded to previous levels the next year. Chile's food regulations were not followed by a sustained decline in obesity in primary- and secondary-school students. Future research should examine whether and how children in Chile and other countries maintain high levels of overweight and obesity despite food regulations designed to reduce consumption of obesogenic foods and beverages.

RESUMEN Se estimaron las tendencias en la prevalencia de la obesidad y el sobrepeso en estudiantes chilenos de educación primaria y secundaria, antes y después de las regulaciones introducidas en Chile en el 2016 sobre la comercialización y disponibilidad de productos hipercalóricos, con un alto contenido de azúcares, sodio o grasas saturadas. Se utilizaron datos del Mapa Nutricional de Chile, una encuesta en la que se midió el índice de masa corporal (IMC) de la población estudiantil de las escuelas públicas. Tomando los umbrales de IMC definidos por la Organización Mundial de la Salud, se calculó la prevalencia del sobrepeso y la obesidad para cada año entre el 2013 y el 2019 en estudiantes de jardín de infancia (4 años), preescolar (5 años), primer grado (6 años) y noveno grado (14 años). En los estudiantes de noveno grado, la prevalencia del sobrepeso y la obesidad aumentó en 2 puntos porcentuales durante los 3 años posteriores a la introducción de las regulaciones del 2016. En el caso de los grupos de jardín de infancia, preescolar y primer grado, el sobrepeso y la obesidad disminuyeron entre 1 y 3 puntos porcentuales un año después de la introducción de las regulaciones, pero al año siguiente volvieron a los niveles anteriores. La introducción de las regulaciones alimentarias de Chile no estuvo seguida de una disminución continua de la obesidad en la población estudiantil de primaria y secundaria. En las investigaciones futuras se deberá examinar si la población infantil de Chile y otros países mantiene niveles altos de sobrepeso y obesidad a pesar de las regulaciones alimentarias diseñadas para reducir el consumo de productos y bebidas obesogénicos, así como las características específicas que adopta este problema de salud.

RESUMO Foram estimadas tendências de prevalência da obesidade e do sobrepeso em alunos chilenos do ensino fundamental e médio antes e depois da regulamentação de 2016 da propaganda e disponibilidade de alimentos com alto teor calórico ou ricos em açúcares totais, sódio ou gorduras saturadas no Chile. Foram utilizados dados obtidos da Pesquisa em Nutrição do Chile, que aferiu o índice de massa corporal (IMC) de escolares da rede pública. Com base nos limiares de IMC definidos pela Organização Mundial da Saúde (OMS), calculou-se a prevalência anual de sobrepeso e obesidade em crianças na pré-escola (4 anos), no jardim da infância (5 anos), no primeiro ano (6 anos) e no nono ano (14 anos) em cada ano no período entre 2013 e 2019. Entre os alunos do nono ano, a prevalência de sobrepeso e obesidade aumentou 2 pontos percentuais nos 3 anos que se seguiram à introdução da regulamentação de 2016. Entre os alunos da pré-escola, do jardim de infância e do primeiro ano, ocorreu uma redução de 1 a 3 pontos percentuais na prevalência de sobrepeso e obesidade um ano após a introdução da regulamentação, mas os níveis voltaram a subir no ano seguinte. A regulamentação de alimentos não resultou em um declínio sustentado da obesidade nos alunos do ensino fundamental e médio do Chile. Pesquisas futuras devem ser realizadas para avaliar se, e como, a prevalência de sobrepeso e obesidade nas crianças chilenas e de outros países se mantém alta a despeito da regulamentação de alimentos visando à redução do consumo de alimentos e bebidas obesogênicos.

Have States Reduced Obesity by Legislating More Physical Activity in Elementary School?

Policy Points Between 1998 and 2016, 24 states and the District of Columbia passed laws meant to increase the time that children spent in physical education (PE) or other school-based physical activity (PA). Schools largely disregarded changes to PE/PA laws, which did not increase the time that children spent in PE or recess and did not reduce body mass index, overweight, or obesity. Closer oversight of schools would be needed to improve compliance with state PE and PA laws. Yet, even with better compliance, we estimate that PE and PA policies would be inadequate to reverse the obesity epidemic. Policies should also address consumption, both inside and outside of school. CONTEXT: To control childhood obesity, leading medical organizations have recommended increasing the time that children spend in physical education (PE) and other school-based physical activity (PA). Yet, it is unknown how many states have passed laws that codify these recommendations, and it is unknown what effect changing state laws has had on obesity or the time that children actually spent in PE and PA. METHODS: We joined state laws to national samples of 13,920 children from two different cohorts of elementary students. One cohort attended kindergarten in 1998; the other attended kindergarten in 2010; both cohorts were followed from kindergarten through fifth grade. We estimated the effects of changes to state laws in a regression with state and year fixed effects. FINDINGS: Twenty-four states and the District of Columbia increased the time that children were recommended or required to spend in PE or PA. These changes in state policies did not increase actual time spent in PE or recess, did not affect average body mass index (BMI) or BMI Z score, and did not affect the prevalence of overweight or obesity. CONCLUSION: Increasing the PE or PA time required or recommended by state laws has not slowed the obesity epidemic. Many schools have failed to comply with state laws. A back-of-the-envelope calculation suggests that, even with better compliance, the legislated changes in PE laws might not have changed energy balance enough to reduce obesity prevalence.

Is Psychological Science Self-Correcting? Citations Before and After Successful and Failed Replications.

In principle, successful replications should enhance the credibility of scientific findings, and failed replications should reduce credibility. Yet it is unknown how replication typically affects the influence of research. We analyzed the citation history of 98 articles. Each was published by a selective psychology journal in 2008 and subjected to a replication attempt published in 2015. Relative to successful replications, failed replications reduced citations of replicated studies by only 5% to 9% on average, an amount that did not differ significantly from zero. Less than 3% of articles citing the original studies cited the replication attempt. It does not appear that replication failure much reduced the influence of nonreplicated findings in psychology. To increase the influence of replications, we recommend (a) requiring authors to cite replication studies alongside the individual findings and (b) enhancing reference databases and search engines to give higher priority to replication studies.

The data revolution comes to higher education: identifying students at risk of dropout in Chile.

Enrolment in higher education has risen dramatically in Latin America, especially in Chile. Yet graduation and persistence rates remain low. One way to improve graduation and persistence is to use data and analytics to identify students at risk of dropout, target interventions, and evaluate interventions' effectiveness at improving student success. We illustrate the potential of this approach using data from eight Chilean universities. Results show that data available at matriculation are only weakly predictive of persistence, while prediction improves dramatically once data on university grades become available. Some predictors of persistence are under policy control. Financial aid predicts higher persistence, and being denied a first-choice major predicts lower persistence. Student success programmes are ineffective at some universities; they are more effective at others, but when effective they often fail to target the highest risk students. Universities should use data regularly and systematically to identify high-risk students, target them with interventions, and evaluate those interventions' effectiveness.

Tonal and "Anti-Tonal" Cognitive Structure in Viennese Twelve-Tone Rows.

We show that the twelve-tone rows of Arnold Schoenberg and Anton Webern are "anti-tonal"-that is, structured to avoid or undermine listener's tonal schemata. Compared to randomly generated rows, segments from Schoenberg's and Webern's rows have significantly lower fit to major and minor key profiles. The anti-tonal structure of Schoenberg's and Webern's rows is still evident when we statistically controlled for their preference for other row features such as mirror symmetry, derived and hexachordal structures, and preferences for certain intervals and trichords. The twelve-tone composer Alban Berg, by contrast, often wrote rows with segments that fit major or minor keys quite well.

Missing children: how Chilean schools evaded accountability by having low-performing students miss high-stakes tests.

High-stakes testing pressures schools to raise test scores, but schools respond to pressure in different ways. Some responses produce real, broad increases in learning, but other responses can raise reported test scores without increasing learning. We estimate the effect of an accountability program on reading scores and math scores in Chile. Over a 6-year period, fourth-grade reading and math scores rose by 0.2 to 0.3 standard deviations, on average, and half the rise was due to the accountability program. However, many schools, especially schools serving disadvantaged students, inflated their accountability ratings by having low-performing students miss high-stakes tests. To encourage healthier responses to accountability, we recommend setting accountability goals that are attainable for schools with disadvantaged students, and providing incentives for all students to take high-stakes tests.

Does more education cause lower BMI, or do lower-BMI individuals become more educated? Evidence from the National Longitudinal Survey of Youth 1979.

More educated adults have lower average body mass index (BMI). This may be due to selection, if adolescents with lower BMI attain higher levels of education, or it may be due to causation, if higher educational attainment reduces BMI gain in adulthood. We test for selection and causation in the National Longitudinal Survey of Youth 1979, which has followed a representative US cohort from age 14-22 in 1979 through age 47-55 in 2012. Using ordinal logistic regression, we test the selection hypothesis that overweight and obese adolescents were less likely to earn high school diplomas and bachelor's degrees. Then, controlling for selection with individual fixed effects, we estimate the causal effect of degree completion on BMI and obesity status. Among 18-year-old women, but not among men, being overweight or obese predicts lower odds of attaining higher levels of education. At age 47-48, higher education is associated with lower BMI, but 70-90% of the association is due to selection. Net of selection, a bachelor's degree predicts less than a 1 kg reduction in body weight, and a high school credential does not reduce BMI.

How much does teacher quality vary across teacher preparation programs? Reanalyses from six states.

At least sixteen US states have taken steps toward holding teacher preparation programs (TPPs) accountable for teacher value-added to student test scores. Yet it is unclear whether teacher quality differences between TPPs are large enough to make an accountability system worthwhile. Several statistical practices can make differences between TPPs appear larger and more significant than they are. We reanalyze TPP evaluations from 6 states-New York, Louisiana, Missouri, Washington, Texas, and Florida-using appropriate methods implemented by our new caterpillar command for Stata. Our results show that teacher quality differences between most TPPs are negligible-.01-0.03 standard deviations in student test scores-even in states where larger differences were reported previously. While ranking all a state's TPPs is not useful, in some states and subjects we can find a single TPP whose teachers are significantly above or below average. Such exceptional TPPs may reward further study.

Understanding differences between summer vs. school obesogenic behaviors of children: the structured days hypothesis.

BACKGROUND: Although the scientific community has acknowledged modest improvements can be made to weight status and obesogenic behaviors (i.e., physical activity, sedentary/screen time, diet, and sleep) during the school year, studies suggests improvements are erased as elementary-age children are released to summer vacation. Emerging evidence shows children return to school after summer vacation displaying accelerated weight gain compared to the weight gained occurring during the school year. Understanding how summer days differ from when children are in school is, therefore, essential. DISCUSSION: There is limited evidence on the etiology of accelerated weight gain during summer, with few studies comparing obesogenic behaviors on the same children during school and summer. For many children, summer days may be analogous to weekend days throughout the school year. Weekend days are often limited in consistent and formal structure, and thus differ from school days where segmented, pre-planned, restrictive, and compulsory components exist that shape obesogenic behaviors. The authors hypothesize that obesogenic behaviors are beneficially regulated when children are exposed to a structured day (i.e., school weekday) compared to what commonly occurs during summer. This is referred to as the 'Structured Days Hypothesis' (SDH). To illustrate how the SDH operates, this study examines empirical data that compares weekend day (less-structured) versus weekday (structured) obesogenic behaviors in U.S. elementary school-aged children. From 190 studies, 155 (~80%) demonstrate elementary-aged children's obesogenic behaviors are more unfavorable during weekend days compared to weekdays. CONCLUSION: In light of the SDH, consistent evidence demonstrates the structured environment of weekdays may help to protect children by regulating obesogenic behaviors, most likely through compulsory physical activity opportunities, restricting caloric intake, reducing screen time occasions, and regulating sleep schedules. Summer is emerging as the critical period where childhood obesity prevention efforts need to be focused. The SDH can help researchers understand the drivers of obesogenic behaviors during summer and lead to innovative intervention development.

Gender and Weight among Thoroughbred Jockeys: Underrepresented Women and Underweight Men.

Discrimination can damage health by limiting an occupation to persons who are physically unsuited to it. In thoroughbred racing, male jockeys damage their health to reach racing weights, while women who could reach those weights more easily are excluded. The authors estimate the number of U.S. men and women who are light enough to work as jockeys and contrast them with the number of male and female jockeys. The authors contrast the distribution of body mass index in the general population and among top jockeys. Male jockeys outnumber female jockeys by 7 to 1, and by 50 to 1 in top races, and these numbers have not declined since the 1990s. Yet among adults who are light enough to work as jockeys, women outnumber men by at least 7 to 1, and women are half as likely to be underweight. Jockeys' health and performance might improve if barriers to women were lowered.

Better Estimates from Binned Income Data: Interpolated CDFs and Mean-Matching.

Researchers often estimate income statistics from summaries that report the number of incomes in bins such as $0 to 10,000, $10,001 to 20,000, …, $200,000+. Some analysts assign incomes to bin midpoints, but this treats income as discrete. Other analysts fit a continuous parametric distribution, but the distribution may not fit well. We fit nonparametric continuous distributions that reproduce the bin counts perfectly by interpolating the cumulative distribution function (CDF). We also show how both midpoints and interpolated CDFs can be constrained to reproduce the mean of income when it is known. We evaluate the methods in estimating the Gini coefficients of all 3,221 U.S. counties. Fitting parametric distributions is very slow. Fitting interpolated CDFs is much faster and slightly more accurate. Both interpolated CDFs and midpoints give dramatically better estimates if constrained to match a known mean. We have implemented interpolated CDFs in the "binsmooth" package for R. We have implemented the midpoint method in the "rpme" command for Stata. Both implementations can be constrained to match a known mean.

From Kindergarten Through Second Grade, U.S. Children's Obesity Prevalence Grows Only During Summer Vacations.

OBJECTIVE: To assess the relative importance of school and nonschool risk factors, this study estimated whether overweight and obesity prevalence grows faster during the school year or during summer vacation. METHODS: In the Early Childhood Longitudinal Study, Kindergarten Class of 2010-11, a nationally representative complex random sample of 18,170 U.S. children was followed from the fall of kindergarten in 2010 through the spring of second grade in 2013. Children's weight and heights were measured in schools each fall and spring. A multilevel growth model was used to estimate growth in mean BMI, overweight prevalence, and obesity prevalence during each summer and each school year. RESULTS: From the fall of kindergarten to the spring of second grade, the prevalence of obesity increased from 8.9% to 11.5%, and the prevalence of overweight increased from 23.3% to 28.7%. All of the increase in prevalence occurred during the two summer vacations; no increase occurred during any of the three school years. CONCLUSIONS: The risk of obesity is higher when children are out of school than when they are in school.

An education gradient in health, a health gradient in education, or a confounded gradient in both?

There is a positive gradient associating educational attainment with health, yet the explanation for this gradient is not clear. Does higher education improve health (causation)? Do the healthy become highly educated (selection)? Or do good health and high educational attainment both result from advantages established early in the life course (confounding)? This study evaluates these competing explanations by tracking changes in educational attainment and Self-rated Health (SRH) from age 15 to age 31 in the National Longitudinal Study of Youth, 1997 cohort. Ordinal logistic regression confirms that high-SRH adolescents are more likely to become highly educated. This is partly because adolescent SRH is associated with early advantages including adolescents' academic performance, college plans, and family background (confounding); however, net of these confounders adolescent SRH still predicts adult educational attainment (selection). Fixed-effects longitudinal regression shows that educational attainment has little causal effect on SRH at age 31. Completion of a high school diploma or associate's degree has no effect on SRH, while completion of a bachelor's or graduate degree have effects that, though significant, are quite small (less than 0.1 points on a 5-point scale). While it is possible that educational attainment would have greater effect on health at older ages, at age 31 what we see is a health gradient in education, shaped primarily by selection and confounding rather than by a causal effect of education on health.

The effects of school physical education grants on obesity, fitness, and academic achievement.

OBJECTIVE: Foundations and governments fund a number of programs that provide grants to improve school physical education or other forms of school-based physical activity. The effects of these grant programs are unknown. We evaluate the effects of Texas Fitness Now, a program in which the state of Texas granted $37 million to improve physical education in high-poverty middle schools over the 4 school years from 2007-08 to 2010-11. The stated goals of Texas Fitness Now were to reduce obesity, increase fitness, and raise academic achievement. METHOD: We summarize how Texas Fitness Now funds were spent and estimate the impact of Texas Fitness Now using a fixed-effects longitudinal model that exploits changes in schools' eligibility over time. Changes in eligibility occurred when eligibility expanded to new schools after year 2 and when the program was terminated after year 4. RESULTS: Most Texas Fitness Now funds were spent on sports and fitness equipment. Smaller amounts were spent on anti-obesity curricula. Texas Fitness Now improved strength and flexibility, especially among girls, but it did not improve BMI or academic achievement, and it had mixed effects on aerobic capacity. The fitness benefits were not lost in the year after the program ended, perhaps because schools kept the equipment that they had bought during their years of eligibility. CONCLUSION: The results of Texas Fitness Now were typical for an intervention that relied almost exclusively on physical activity. Programs that improve BMI as well as fitness tend to have a more fully developed nutrition component.