The timing of the rise in U.S. obesity varies with measure of fatness

Obesity and labour market outcomes in Italy: a dynamic panel data evidence with correlated random effects

This paper investigates the effects of obesity, socio-economic variables, and individual-specific factors on work productivity across Italian regions. A dynamic panel data with correlated random effects is used to jointly deal with incidental parameters, endogeneity issues, and functional forms of misspecification. Methodologically, a hierarchical semiparametric Bayesian approach is involved in shrinking high dimensional model classes, and then obtaining a subset of potential predictors affecting outcomes. Monte Carlo designs are addressed to construct exact posterior distributions and then perform accurate forecasts. Cross-sectional Heterogeneity is modelled nonparametrically allowing for correlation between heterogeneous parameters and initial conditions as well as individual-specific regressors. Prevention policies and strategies to handle health and labour market prospects are also discussed.

Associations Between Adult Triceps Skinfold Thickness and All-Cause, Cardiovascular and Cerebrovascular Mortality in NHANES 1999–2010: A Retrospective National Study

Background:

The association between triceps skinfold (TSF) thickness and mortality in previous studies was controversial. This study aimed to explore how TSF thickness affects all-cause, cardiovascular, and cerebrovascular mortality among the United States (U.S.) general population.

Methods

Our research included 25,954 adults in the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2010. Participants were categorized by the baseline TSF quartiles [quartile 1 (Q1): < 11.8, (Q2): 11.8–17.4, (Q3): 17.4–25, and (Q4): ≥25; unit: millimeter (mm)]. Cox regression models were used to assess the association of TSF with all-cause, cardiovascular, and cerebrovascular mortality. The association between mid-arm muscle circumference (MAMC) and mortality was also explored. Subgroup analyses were conducted to assess heterogeneity in different subgroups.

Results

The highest TSF group (Q4) had the lowest risk to experience all-cause (HR, 0.46; 95% CI, 0.38–0.59; P < 0.001) and cardiovascular mortality (HR, 0.35; 95% CI, 0.23–0.54; P < 0.001) than the lowest TSF group (Q1) after multivariate adjustment. However, there was no relationship between TSF quartiles and cerebrovascular mortality (HR, 0.98; 95%CI, 0.42–2.30; P = 0.97). The protective effects of TSF thickness on mortality still existed after adjusting for BMI and MAMC. For every 1 mm increase in TSF thickness, the risk of all-cause and cardiovascular death decreased by 4% (HR, 0.96; 95% CI, 0.95–0.97; P < 0.001) and 6% (HR, 0.94; 95% CI, 0.93–0.96; P < 0.001), respectively. In the stratified analysis, the relationships between TSF and mortality risk were generally similar across all subgroups.

Conclusions

Higher TSF thickness was associated with lower all-cause and cardiovascular mortality, independent of BMI and MAMC. Our study revealed that the TSF thickness may be a convenient and credible indicator to predict mortality, especially in those with severe cardiovascular diseases.

The Association of Subscapular Skinfold with All-Cause, Cardiovascular and Cerebrovascular Mortality

Purpose

Previous studies suggested inconsistent relationship between subscapular skinfold and all-cause, cardiovascular, and cerebrovascular mortality. Therefore, the present study aimed to investigate the associations between subscapular skinfold with all-cause, cardiovascular, and cerebrovascular mortality.

Patients and Methods

Data were collected from the National Health and Nutrition Examination Survey (NHANES, 1999–2006) with follow-up data through 31 December 2015. Participants were categorized by subscapular skinfold quartiles. The hazard ratios (HRs) and 95% confidence intervals (CIs) were evaluated using the multivariate Cox regression model and subgroup analysis. Kaplan–Meier curves were used to present cause-specific mortalities and used Cox cubic regression splines to examine the association of subscapular skinfold with cause-specific mortalities.

Results

A total of 16,402 subjects (49.61% male) were involved in our study. After a mean follow-up of 141.73 months, there were 3078 (18.77%), 392 (2.39%), and 128 (0.78%) cases of all-cause, cardiovascular, and cerebrovascular mortality, respectively. Participants in the highest quartile of subscapular skinfold (≥24.80mm) versus the lowest (<13.20mm) had lower risk for all-cause mortality (HR, 0.71; 95% CI, 0.57–0.89; P for trend = 0.007) and cardiovascular mortality (HR, 0.44; 95% CI, 0.23–0.83; P for trend = 0.023) in the fully adjusted model. In the age-stratified analysis, subscapular skinfold was only inversely associated with all-cause and cardiovascular disease mortality in people ≥65 years of age (all P-interaction <0.001). No significant difference was found between subscapular skinfold and cerebrovascular mortality (all P > 0.05).

Conclusion

Subscapular skinfold showed an inverse association with all-cause and cardiovascular disease mortality in people aged ≥65 years.

Does global warming contribute to the obesity epidemic?

Endotherms must expend more energy to digest colder food, so they acquire more calories by eating food at a higher temperature than eating the identical food cold. A recent study shows that ownership of a microwave is associated with a small increase in BMI and obesity. The same logic applies to other substances that endotherms introduce into their bodies, like air. An analysis of the National Longitudinal Study of Adolescent to Adult Health (Add Health) shows that, net of sex, age, race, education, earnings, neighborhood characteristics, and exercise activities, atmospheric temperature is associated with small but statistically significant increases in BMI, weight, overweight, and obesity. Atmospheric temperature is more strongly associated than most exercise activities, and as strongly associated as age and population density. An average American might reduce weight by 15.1 lbs, BMI by 2.52 (half the difference between normal weight and obesity), and the odds of obesity by 54% by moving from Phoenix, AZ, to Barrow, AK, or, less dramatically, 5.7 lbs in weight, .95 in BMI (a fifth of the difference between normal weight and obesity), and 25% in the odds of obesity by moving mere 150 miles north to Flagstaff, AZ. Global warming under the worst-case scenario might produce an increase of 2.2 lbs in weight, .37 in BMI, and 12% in odds of obesity from 1961 to 2081.

An Evolutionary Perspective on the Obesity Epidemic

An evolutionary approach to obesity involves a genomic/anthropological dimension. For 1.8 Myr the lifestyle of hunter-gatherers (HGs) comprised intense physical activity and a high-protein/low-carbohydrate diet. Genomes of HGs were adapted to low insulin sensitivity. When the agrarian epoch began a new 'farmer diet' high in carbohydrates (CHO) emerged. Owing to periodic famines, the genome may not have adapted; they preserved a HG genome. Ever since the industrial revolution our genome is adapting rapidly to a CHO-rich diet. Individuals with preserved HG genome develop obesity at age 4-8 years and need a low-CHO diet. By contrast, those with a farmer genome become obese in infancy; they need a low-calorie diet. This knowledge prompts exploration of the two genomes and their clinical presentations.

The Potential Effects of Obesity on Social Security Claiming Behavior and Retirement Benefits

Objectives

Obesity prevalence among Americans has increased for nearly three decades. We explore the relationship between the rise in obesity and Social Security retirement benefit claiming, a decision impacting nearly all aging Americans. Specifically, we investigate whether obesity can affect individuals' decision to claim benefits early, a choice that has important implications for financial security in retirement, particularly for those with lower socioeconomic status (SES).

Method

We use a microsimulation model called MINT6 (Modeling Income in the Near Term, version 6) to demonstrate the potential effects of obesity on subjective life expectancy and claiming behavior. We impute obesity status using data from the National Health and Nutrition Examination Survey (NHANES), which describes the distribution of obesity prevalence within the United States by gender, poverty status, and race/ethnicity.

Results

We find that the rise in obesity and the consequent incidence of obesity-related diseases may lead some individuals to make claiming decisions that lead to lower monthly and lifetime Social Security retirement benefits. Further, we find that the potential economic impact of this decision is larger for those with lower SES.

Discussion

We present a behavioral perspective by addressing the potential effects that obesity can have on individuals' retirement decisions and their resulting Social Security retirement benefits.

Can Obesity Cause Depression? A Pseudo-panel Analysis

Objectives

The US ranks ninth in obesity in the world, and approximately 7% of US adults experience major depressive disorder. Social isolation due to the stigma attached to obesity might trigger depression.

Methods

This paper examined the impact of obesity on depression. To overcome the endogeneity problem, we constructed pseudopanel data using the Behavioral Risk Factor Surveillance System from 1997 to 2008.

Results

The results were robust, and body mass index (BMI) was found to have a positive effect on depression days and the percentage of depressed individuals in the population.

Conclusions

We attempted to overcome the endogeneity problem by using a pseudo-panel approach and found that increases in the BMI increased depression days (or being depressed) to a statistically significant extent, with a large effect size.

The Effect of Medical Marijuana Laws on Body Weight

This study is the first to examine the effects of medical marijuana laws (MMLs) on body weight, physical wellness, and exercise. Using data from the 1990 to 2012 Behavioral Risk Factor Surveillance System and a difference-in-difference approach, we find that the enforcement of MMLs is associated with a 2% to 6% decline in the probability of obesity. We find some evidence of age-specific heterogeneity in mechanisms. For older individuals, MML-induced increases in physical mobility may be a relatively important channel, while for younger individuals, a reduction in consumption of alcohol, a substitute for marijuana, appears more important. These findings are consistent with the hypothesis that MMLs may be more likely to induce marijuana use for health-related reasons among older individuals, and cause substitution toward lower-calorie recreational 'highs' among younger individuals. Our estimates suggest that MMLs induce a $58 to $115 per-person annual reduction in obesity-related medical costs. Copyright © 2015 John Wiley & Sons, Ltd.

Secular trends for skinfolds differ from those for BMI and waist circumference among adults examined in NHANES from 1988-1994 through 2009-2010

BACKGROUND

Although the prevalence of a body mass index [BMI (in kg/m²)] ≥30 has tripled among US adults since the 1960s, BMI is only moderately correlated with body fatness. Because skinfolds can more accurately estimate body fatness than can BMI, it is possible that skinfolds could be useful in monitoring secular trends in body fatness.

OBJECTIVE

We examined whether there were similar secular trends for skinfolds (triceps and subscapular), BMI, and waist circumference between US adults.

DESIGN

This study was an analysis of 45,754 adults who participated in the NHANES from 1988-1994 through 2009-2010. Approximately 19% of the subjects were missing ≥1 skinfold-thickness measurement. These missing values were imputed from other characteristics.

RESULTS

Trends in mean levels and in the prevalence of high levels of the 4 body size measures were fairly similar between men, with mean levels increasing by ≥5% from 1988-1994 through 2009-2010. Slightly larger increases were seen in women for BMI and waist circumference (7-8%), but trends in skinfolds were markedly different. The mean triceps skinfold, for example, increased by 2 mm through 2003-2004, but subsequently decreased so that the mean in 2009-2010 did not differ from that in 1988-1994. Compared with obese women in 1988-1994, the mean BMI of obese women in 2009-2010 was 1 higher, but mean levels of both skinfolds were 5-10% lower.

CONCLUSIONS

Although there were fairly similar trends in levels of BMI, waist circumference, and skinfold thicknesses in men in the United States from 1988-1994 through 2009-2010, there were substantial differences in women. Our results indicate that it is unlikely that skinfold thicknesses could be used to monitor trends in obesity.

Does Anything Work to Reduce Obesity? (Yes, Modestly)

A large number and range of policies to address the obesity epidemic have been implemented. However, the prevalence of obesity has continued to rise, or at best has leveled off, and many individual interventions have had disappointing results. This has led some people to question whether anything works to prevent or reduce obesity. In this essay I review the evidence on the effectiveness of antiobesity programs. Although some programs have had negligible effects, others have had small beneficial effects on diet, physical activity, and weight. Nutrition labels on packaged foods and calorie labels on menus have led to healthful reformulations of foods. Offering incentives for children to choose healthy foods, and for adults to go to the gym, have proven effective at changing behaviors. Precommitment mechanisms such as deposit contracts for weight loss and bariatric surgery are associated with weight loss but may not be ideal solutions for the majority of obese individuals. Certain comprehensive school-based interventions to change children's diets and promote physical activity have proved cost-effective. There is no magic bullet that will solve the problem of obesity, but numerous policies with modest beneficial effects, if enacted jointly, could result in meaningful change.

Reporting error in weight and its implications for bias in economic models

Most research on the economic consequences of obesity uses data on self-reported weight, which contains reporting error that has the potential to bias coefficient estimates in economic models. The purpose of this paper is to measure the extent and characteristics of reporting error in weight, and to examine its impact on regression coefficients in models of the healthcare consequences of obesity. We analyze data from the National Health and Nutrition Examination Survey (NHANES) for 2003-2010, which includes both self-reports and measurements of weight and height. We find that reporting error in weight is non-classical: underweight respondents tend to overreport, and overweight and obese respondents tend to underreport, their weight, with underreporting increasing in measured weight. This error results in roughly 1 out of 7 obese individuals being misclassified as non-obese. Reporting error is also correlated with other common regressors in economic models, such as education. Although it is a common misconception that reporting error always causes attenuation bias, comparisons of models that use self-reported and measured weight confirm that reporting error can cause upward bias in coefficient estimates. For example, use of self-reports leads to overestimates of the probability that an obese man uses a prescription drug, has a healthcare visit, or has a hospital admission. These findings underscore that models of the consequences of obesity should use measurements of weight, when available, and that social science datasets should measure weight rather than simply ask subjects to report their weight.

Menthol cigarette smoking and obesity in young adult daily smokers in Hawaii

This study investigates 1) the relationship between menthol cigarette smoking and obesity and 2) the association of body mass index with the nicotine metabolite ratio among menthol and non-menthol daily smokers aged 18–35 (n = 175). A brief survey on smoking and measures of height and weight, carbon monoxide, and saliva samples were collected from participants from May to December 2013 in Honolulu, Hawaii. Multiple regression was used to estimate differences in body mass index among menthol and non-menthol smokers and the association of menthol smoking with obesity. We calculated the log of the nicotine metabolite ratio to examine differences in the nicotine metabolite ratio among normal, overweight, and obese smokers. Sixty-eight percent of smokers used menthol cigarettes. Results showed that 62% of normal, 54% of overweight, and 91% of obese smokers used menthol cigarettes (p = .000). The mean body mass index was significantly higher among menthol compared with non-menthol smokers (29.4 versus 24.5, p = .000). After controlling for gender, marital status, educational attainment, employment status, and race/ethnicity, menthol smokers were more than 3 times as likely as non-menthol smokers to be obese (p = .04). The nicotine metabolite ratio was significantly lower for overweight menthol smokers compared with non-menthol smokers (.16 versus .26, p = .02) in the unadjusted model, but was not significant after adjusting for the covariates. Consistent with prior studies, our data show that menthol smokers are more likely to be obese compared with non-menthol smokers. Future studies are needed to determine how flavored tobacco products influence obesity among smokers.

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Young adult menthol smokers had a higher body mass index than non-menthol smokers.

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Nearly 91% of young adult obese daily smokers used menthol cigarettes.

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Daily menthol smokers were 3 times as likely to be obese than non-menthol smokers.

An economy of scales: A selective review of obesity's economic causes, consequences, and solutions

This paper reviews the economic research on obesity, covering topics such as the measurement of, and trends in, obesity, the economic causes of obesity (e.g. the monetary price and time cost of food, food assistance programs, income, education, macroeconomic conditions, and peer effects), and the economic consequences of obesity (e.g. lower wages, a lower probability of employment, and higher medical care costs). It also examines the extent to which obesity imposes negative externalities, and economic interventions that could potentially internalize such externalities, such as food taxes, subsidies for school-based physical activity programs, and financial rewards for weight loss. It discusses other economic rationales for government intervention with respect to obesity, such as imperfect information, time inconsistent preferences, and irrational behavior. It concludes by proposing a research agenda for the field. Overall, the evidence suggests that there is no single dominant economic cause of obesity; a wide variety of factors may contribute a modest amount to the risk. There is consistent evidence regarding the economic consequences of obesity, which are lower wages and higher medical care costs that impose negative externalities through health insurance. Studies of economic approaches to preventing obesity, such as menu labeling, taxes on energy-dense foods, and financial rewards for weight loss find only modest effects on weight and thus a range of policies may be necessary to have a substantial effect on the prevalence of obesity.

Savings in Medical Expenditures Associated with Reductions in Body Mass Index Among US Adults with Obesity, by Diabetes Status

BACKGROUND

The prevalence of obesity has more than doubled in the USA in the past 30 years. Obesity is a significant risk factor for diabetes, cardiovascular disease, and other clinically significant co-morbidities. This paper estimates the medical care cost savings that can be achieved from a given amount of weight loss by people with different starting values of body mass index (BMI), for those with and without diabetes. This information is an important input into analyses of the cost effectiveness of obesity treatments and prevention programs.

METHODS

Two-part models of instrumental variables were estimated using data from the Medical Expenditure Panel Survey (MEPS) for 2000-2010. Models were estimated for all adults as well as separately for those with and without diabetes. We calculated the causal impact of changes in BMI on medical care expenditures, cost savings for specific changes in BMI (5, 10, 15, and 20 %) from starting BMI levels ranging from 30 to 45 kg/m(2), as well as the total excess medical care expenditures caused by obesity.

RESULTS

In the USA, adult obesity raised annual medical care costs by $US3,508 per obese individual, for a nationwide total of $US315.8 billion (year 2010 values). However, the relationship of medical care costs over BMI is J-shaped; costs rise exponentially in the range of class 2 and 3 obesity (BMI ≥35). The heavier the obese individual, the greater the reduction in medical care costs associated with a given percent reduction in BMI. Medical care expenditures are higher, and rise more with BMI, among individuals with diabetes than among those without diabetes.

CONCLUSIONS

The savings from a given percent reduction in BMI are greater the heavier the obese individual, and are greater for those with diabetes than for those without diabetes. The results provide health insurers, employers, government agencies, and health economists with accurate estimates of the change in medical care expenditures resulting from weight loss, which is important information for calculating the cost effectiveness of interventions to prevent and treat obesity.

Measuring obesity in the absence of a gold standard

Reliable measures of body composition are essential to develop effective policies to tackle obesity. The lack of an acceptable gold-standard for measuring fatness has made it difficult to evaluate alternative measures of obesity. We use latent class analysis to characterise existing diagnostics. Using data on US adults we show that measures based on body mass index and bioelectrical impedance analysis misclassify large numbers of individuals. For example, 45% of obese White women are misclassified as non-obese using body mass index, while over 50% of non-obese White women are misclassified as being obese using bioelectrical impedance analysis. In contrast the misclassification rates are low when waist circumference is used to measure obesity. These results have important implications for our understanding of differences in obesity rates across time and groups, as well as posing challenges for the econometric analysis of obesity.

Misreporting and misclassification: implications for socioeconomic disparities in body-mass index and obesity

Body-mass index (BMI) has become the standard proxy for obesity in social science research. This study deals with the potential problems related to, first, relying on self-reported weight and height to calculate BMI (misreporting), and, second, the concern that BMI is a deficient measure of body fat (misclassification). Using a regional Swedish sample, we analyze whether socioeconomic disparities in BMI are biased because of misreporting, and whether socioeconomic disparities in the risk of obesity are sensitive to whether BMI or waist circumference is used to define obesity. Education and income are used as socioeconomic indicators. The overall conclusion is that misreporting and misclassification may indeed matter for estimated educational and income disparities in BMI and obesity. In the misreporting part we find that women with higher education misreport less than those with lower education, leading to underestimation of the education disparity when using self-reported information. In the misclassification part we find that the probability of being misclassified decreases with income, for both men and women. Among women, the consequence is a steeper income gradient when obesity is defined using waist circumference instead of BMI. Among men the income gradient is statistically insignificant irrespective of how obesity is defined, but when estimating the probability of obesity defined by waist circumference, an educational gradient, which is not present when classifying men using BMI, arises.

Financial hardship and obesity

There is a substantial correlation between household debt and health. Individuals with less healthy lifestyles are more likely to hold debt, yet there is little evidence as to whether this is merely a correlation or if financial hardship actually causes obesity. In this paper, we use data from the National Longitudinal Survey of Adolescent Health to test whether financial hardship affects body weight. We divide our sample into two groups: men and women, explore two different types of financial hardship: holding credit card debt and having trouble paying bills, and three outcomes: overweight, obese and body mass index (BMI). We use a variety of econometric techniques: Ordinary Least Squares, Propensity Score Matching, Sibling Fixed Effects, and Instrumental Variables to investigate the relationship that exists between financial hardship and body weight. In addition, we conduct several robustness checks. Although our OLS and PSM results indicate a correlation between financial hardship and body weight these results appear to be largely driven by unobservables. Our IV results suggest that there is no causal relationship between credit card debt and overweight or obesity for either men or women. However, we find suggestive evidence that having trouble paying bills may be a cause of obesity for women.

Association between obesity and prescribed medication use in England

We investigate the association between obesity and use of prescribed medications in England. Data were taken from fourteen rounds of the Health Survey for England (1999-2012), which has measures of current prescribed medication use based on therapeutic classifications in the British National Formulary, and nurse-measured height and weight. We find that obesity has a statistically significant and positive association with use of a range of medicines for managing diseases associated with obesity. The mean probability of using any type of medication is 0.40 in those of normal weight, 0.44 in the overweight, 0.52 in obesity class I and 0.60 in obesity class II/III. Significant positive associations were found between obesity and the use of medication for diseases of the cardiovascular system, gastrointestinal system, respiratory system, and central nervous system, as well as for infections, endocrine system disorders, gynaecological/urinary disorders and musculoskeletal and joint disorders. Use of anti-obesity medication is low, even among those with class II/III obesity.

High frequency body mass measurement, feedback, and health behaviors

We analyze weight and fat percentage measurements of respondents in an online general population panel in the Netherlands, collected using wireless scales, with an average frequency of 1.6 measurements per week. First, we document the existence of a weekly cycle; body mass is lowest on Fridays and highest on Mondays, showing significant (p<0.01) differences of, on average, 0.2 kilogram in weight, 0.06 in BMI value, and 0.03 in fat percentage. Second, we find that in the general population fat-based measures of obesity point at a three times larger prevalence of obesity (53%) than BMI-based measures (17%). Third, we find that feedback that includes a recommended weight range increases the temporal variation in individual body mass by almost ten percent (sd for weight increases from 1.13 to 1.22; sd for BMI increases from 0.37 to 0.41; sd for fat percentage increases from 0.55 to 0.61.

Macronutrients and obesity: revisiting the calories in, calories out framework

Recent clinical research has studied weight responses to varying diet composition, but the contribution of changes in macronutrient intake and physical activity to rising population weight remains controversial. Research on the economics of obesity typically assumes a "calories in, calories out" framework, but a weight production model separating caloric intake into carbohydrates, fat, and protein, has not been explored in an economic framework. To estimate the contributions of changes in macronutrient intake and physical activity to changes in population weight, we conducted dynamic time series and structural VAR analyses of U.S. data between 1974 and 2006 and a panel analysis of 164 countries between 2001 and 2010. Findings from all analyses suggest that increases in carbohydrates are most strongly and positively associated with increases in obesity prevalence even when controlling for changes in total caloric intake and occupation-related physical activity. Our structural VAR results suggest that, on the margin, a 1% increase in carbohydrates intake yields a 1.01 point increase in obesity prevalence over 5 years while an equal percent increase in fat intake decreases obesity prevalence by 0.24 points.

The effect of school district nutrition policies on dietary intake and overweight: a synthetic control approach

School nutrition policies aim to eliminate ubiquitous unhealthy foods and beverages from schools to improve adolescent dietary behavior and reduce childhood obesity. This paper evaluates the impact of an early nutrition policy, Los Angeles Unified School District's food-and-beverage standards of 2004, using two large datasets on food intake and physical measures. I implement cohort and cross-section estimators using "synthetic" control groups, combinations of unaffected districts that are reweighted to closely resemble the treatment unit in the pre-intervention period. The results indicate that the policy was mostly ineffective at reducing the prevalence of overweight or obesity 8-15 months after the intervention but significantly decreased consumption of two key targets, soda and fried foods. The policy's impact on physical outcomes appears to be mitigated by substitution toward foods that are still (or newly) available in the schools.

Variation in the relationship between BMI and survival by socioeconomic status in Great Britain

We investigate the relationship between obesity and survival, and the extent to which this relationship varies by socioeconomic status (SES). The underlying model is based on the "Pathways to health" framework in which SES affects health by modifying the relationship between lifestyles and health. We use data from the British Health and Lifestyle Survey (1984-1985) and the longitudinal follow-up in June 2009, and run parametric Gompertz survival models to investigate the association between obesity and survival, also accounting for interactions between obesity and both age and SES. Generally we find that obesity is negatively associated with survival, and that SES is positively associated with survival, in both men and women. The interactions between obesity and SES predict survival among women but not among men. Obesity compared with normal weight is associated with a reduction in survival of 3.3, 3.2 and 2.8 years in men aged 40, 50 and 60 years, respectively. Corresponding numbers among women in the lowest SES group are 13.1, 9.7 and 6.1 years, respectively; in the highest SES group they are 6.2, 3.1 and 0.1 years, respectively, a difference of approximately 6 years between the highest and lowest SES groups.

Neighborhood socioeconomic status and BMI differences by immigrant and legal status: evidence from Utah

We build on recent work examining the BMI patterns of immigrants in the US by distinguishing between legal and undocumented immigrants. We find that undocumented women have relative odds of obesity that are about 10 percentage points higher than for legal immigrant women, and their relative odds of being overweight are about 40 percentage points higher. We also find that the odds of obesity and overweight status vary less across neighborhoods for undocumented women than for legal immigrant women. These patterns are not found among immigrant men: undocumented men have lower rates of obesity (by about 6 percentage points in terms of relative odds) and overweight (by about 12 percentage points) than do legal immigrant men, and there is little variation in the impact of neighborhood context across groups of men. We interpret these findings in terms of processes of acculturation among immigrant men and women.

Body mass index, waist circumference and employment: evidence from older Irish adults

Data from the first wave of the Irish Longitudinal Study on Ageing are used to examine the relationship between fatness and obesity and employment status among older Irish adults. Employment status is regressed on one of the following measures of fatness: BMI and waist circumference entered linearly as continuous variables and obesity as a categorical variable defined using both BMI and waist circumference. Controls for demographic and socioeconomic characteristics, socioeconomic characteristics in childhood and physical, mental and behavioural health are also included. The regression results for women indicate that all measures of fatness are negatively associated with the probability of being employed and that the employment elasticity associated with waist circumference is larger than the elasticity associated with BMI. The results for men indicate that employment is not significantly associated with BMI and waist circumference when these are entered linearly in the regression, but it is significantly and negatively associated with obesity defined either using BMI or waist circumference as categorical variables. The results also indicate that the negative association between obesity and employment status is larger among women. For example, the probability of being employed for the obese category defined using BMI is around 8 percentage points lower for women and 5 percentage points lower for men.

Absolute wealth and world region strongly predict overweight among women (ages 18-49) in 360 populations across 36 developing countries

This paper proposes a benchmark for comparing SES gradients across countries, based on gross domestic product apportioned to members of differing wealth categories within countries. Using this approach, we estimate absolute wealth in 360 populations in 36 developing countries and model its relationship with overweight (BMI≥25) among non-pregnant women ages 18-49. A simple model based on absolute wealth alone strongly predicts odds of overweight (R(2)=0.59), a relationship that holds both between countries and between different groups in the same country (10 populations for each of 36 countries). Moreover, world region modifies this relationship, accounting for an additional 22% of variance (R(2)=0.81). This allows us to extract a basic pattern: rising rates of overweight in lower and middle income countries closely track increasing economic resources, and the shape of that gradient differs by region in systematic ways.

Adult obesity: panel study from native Amazonians

This paper examines three morphological indicators measuring obesity among a native Amazonian population of foragers-farmers in Bolivia (Tsimane') and estimates the associations between them and standard covariates of obesity (e.g., socioeconomic status [SES]). We collected annual data from 350 non-pregnant women and 385 men ≥20 years of age from all 311 households in 13 villages during five consecutive years (2002-2006). We used three indicators to measure obesity: body-mass index (BMI), waist circumference (WC), and body fat using bioelectrical impedance analysis (BF-BIA). We ran separate individual random-effect panel multiple regressions for women and men with wealth, acculturation, health, and household food availability as key covariates, and controlled for village and year fixed effects and village×year interaction effects. Although BMI increases by a statistically significant annual growth rate of 0.64% among women and 0.37% among men over the five years, the increase does not yield significant biological meanings. Neither do we find consistent and biologically meaningful covariates associated with adult obesity.

Childhood intelligence and adult obesity

OBJECTIVE

Recent studies conclude childhood intelligence has no direct effect on adult obesity net of education, but evolutionary psychological theories suggest otherwise.

DESIGN AND METHODS

A population (n = 17,419) of British babies has been followed since birth in 1958 in a prospectively longitudinal study. Childhood general intelligence is measured at 7, 11, and 16, and adult BMI and obesity are measured at 51.

RESULTS

Childhood general intelligence has a direct effect on adult BMI, obesity, and weight gain, net of education, earnings, mother's BMI, father's BMI, childhood social class, and sex. More intelligent children grow up to eat more healthy foods and exercise more frequently as adults.

CONCLUSION

Childhood intelligence has a direct effect on adult obesity unmediated by education or earnings. General intelligence decreases BMI only in adulthood when individuals have complete control over what they eat.

Birth cohort effects among US-born adults born in the 1980s: foreshadowing future trends in US obesity prevalence

BACKGROUND

Obesity prevalence stabilized in the US in the first decade of the 2000s. However, obesity prevalence may resume increasing if younger generations are more sensitive to the obesogenic environment than older generations.

METHODS

We estimated cohort effects for obesity prevalence among young adults born in the 1980s. Using data collected from the National Health and Nutrition Examination Survey between 1971 and 2008, we calculated obesity for respondents aged between 2 and 74 years. We used the median polish approach to estimate smoothed age and period trends; residual non-linear deviations from age and period trends were regressed on cohort indicator variables to estimate birth cohort effects.

RESULTS

After taking into account age effects and ubiquitous secular changes, cohorts born in the 1980s had increased propensity to obesity versus those born in the late 1960s. The cohort effects were 1.18 (95% CI: 1.01, 1.07) and 1.21 (95% CI: 1.02, 1.09) for the 1979-1983 and 1984-1988 birth cohorts, respectively. The effects were especially pronounced in Black males and females but appeared absent in White males.

CONCLUSIONS

Our results indicate a generational divergence of obesity prevalence. Even if age-specific obesity prevalence stabilizes in those born before the 1980s, age-specific prevalence may continue to rise in the 1980s cohorts, culminating in record-high obesity prevalence as this generation enters its ages of peak obesity prevalence.

The effect of fat mass on educational attainment: examining the sensitivity to different identification strategies

The literature that examines the relationship between child or adolescent Body Mass Index (BMI) and academic attainment generally finds mixed results. This may be due to the use of different data sets, conditioning variables, or methodologies: studies either use an individual fixed effects (FE) approach and/or an instrumental variable (IV) specification. Using one common dataset, the Avon Longitudinal Study of Parents and Children, and a common set of controls, this paper compares the different approaches (including using different types of IV's), discusses their appropriateness, and contrasts their findings. We show that, although the results differ depending on the approach, most estimates cannot be statistically distinguished from OLS, nor from each other. Examining the potential violations of key assumptions of the different approaches and comparing their point estimates, we conclude that fat mass is unlikely to be causally related to academic achievement in adolescence.

Maternal employment and childhood obesity: a search for mechanisms in time use data

A substantial body of research documents that maternal employment is associated with childhood obesity. This paper explores possible mechanisms for that correlation in the American Time Use Survey (ATUS). We find that maternal employment is associated with working mothers spending, per day, 4 fewer minutes grocery shopping, 17 fewer minutes cooking, 10 fewer minutes eating with children, 12 fewer minutes playing with children, 4 fewer minutes supervising children, and 37 fewer minutes caring for children. The differences tend to be greatest for mothers with young children (age 0-5 years). We explore the extent to which these findings differ by day of the week, whether a partner or spouse is present in the household, whether the mother works non-standard hours, and socioeconomic status. Only a small percentage (about 15%) of the fewer minutes spent in these activities by working mothers appears to be offset by increases in time by husbands and partners. These findings suggest plausible mechanisms for the association between maternal employment and childhood obesity.

Marriage, gender and obesity in later life

A large body of literature argues that marriage promotes health and increases longevity. But do these benefits extend to maintaining a healthy body weight, as the economic theory of health investment suggests they should? They do not. Using the Health and Retirement Study (HRS), I find that entry into marriage among both men and women aged 51-70 is associated with weight gain and exit from marriage with weight loss. I evaluate three additional theories with respect to the cross-sectional and longitudinal variation in the data. First, it may be that a broader set of shared risk factors (such as social obligations regarding meals) raises body mass for married couples. However, the shared risk factor model predicts that the intra-couple correlation should increase with respect to marital duration. Instead, it declines. Second, scholars have recently promoted a "crisis" model of marriage in which marital transitions, not marital status, determine differences in body mass. The crisis model is consistent with short-term effects seen for divorce, but not for the persistent weight gains associated with marriage or the persistent weight loss following widowhood. And transition models, in general, cannot explain significant cross-sectional differences across marital states in a population that is no longer experiencing many transitions, nor can it account for the prominent gender differences (in late middle-age, the heaviest group is unmarried women and the lightest are unmarried men). Third, I argue that pressures of the marriage market, in combination with gendered preferences regarding partner BMI, can account for all the longitudinal and cross-sectional patterns found in the data.

Unfit for service: the implications of rising obesity for US military recruitment

This paper contributes to the literature on the labor market consequences of unhealthy behaviors and poor health by examining a previously underappreciated consequence of the rise in obesity in the USA: challenges for military recruitment. Specifically, this paper estimates the percentage of the US military-age population that exceeds the US Army's current active duty enlistment standards for weight-for-height and percent body fat, using data from the series of National Health and Nutrition Examination Surveys that spans 1959-2008. We calculate that the percentage of military-age adults ineligible for enlistment because they are overweight and overfat more than doubled for men and tripled for women during that time. As of 2007-2008, 5.7 million men and 16.5 million women exceeded the Army's enlistment standards for weight and body fat. We document disparities across race and education in exceeding the standards and estimate that a further rise of just 1% in weight and body fat would further reduce eligibility for military service by over 850 000 men and 1.3 million women. The paper concludes with a discussion of the implications of these findings for military recruitment and defense policy.

The medical care costs of obesity: an instrumental variables approach

This paper is the first to use the method of instrumental variables (IV) to estimate the impact of obesity on medical costs in order to address the endogeneity of weight and to reduce the bias from reporting error in weight. Models are estimated using restricted-use data from the Medical Expenditure Panel Survey for 2000-2005. The IV model, which exploits genetic variation in weight as a natural experiment, yields estimates of the impact of obesity on medical costs that are considerably higher than the estimates reported in the previous literature. For example, obesity is associated with $656 higher annual medical care costs, but the IV results indicate that obesity raises annual medical costs by $2741 (in 2005 dollars). These results imply that the previous literature has underestimated the medical costs of obesity, resulting in underestimates of the economic rationale for government intervention to reduce obesity-related externalities.

Early-life environment, height and BMI of young men in Italy

This paper explores the relationship between the two main dimensions of early-life environment, namely disease burden (measured by infant mortality) and economic conditions (measured by income or consumption per capita), and height and body-mass index (BMI) for six annual cohorts of young Italian men born between 1973 and 1978. By combining micro-level data on height and weight with regional- and province-level information, we are able to link individual height and BMI at age 18 to regional and provincial averages of environmental variables in the year of birth. Our results are consistent with the hypothesis that, in rich low-mortality settings, the negative effects of childhood disease dominate the positive selection effects of mortality. We find that both income and disease matter, although income matters more than disease for height, while the opposite is true for BMI.

The trend of BMI values of US adults by deciles, birth cohorts 1882-1986 stratified by gender and ethnicity

We estimate trends in BMI values by deciles of the US adult population by birth cohorts 1882-1986 stratified by ethnicity and gender. The highest decile increased by some 18-22 BMI units in the course of the century while the lowest ones increased by merely 1-3 BMI units. For example, a typical African American woman in the 10th percentile and 64 in. (162.6 cm) tall increased in weight by just 12 pounds (5 kg) whereas in the 90th percentile her weight would have increased by 128 pounds (58 kg). Hence, the BMI distribution became increasingly right skewed as the distance between the deciles increased considerably. The rate of change of the BMI decile curves varied greatly over time and across gender and ethnicity. The BMI deciles of white men and women experienced upswings after the two world wars and downswings during the Great Depression and also decelerated after 1970. However, among African Americans the pattern is different during the first half of the century with men's rate of increase in BMI values decreasing substantially and that of females remaining constant at a relatively high level until the Second World War. After the war, though, the rate of change of BMI values of blacks came to resemble that of whites with an accelerating phase followed by a slowdown around the 1970s.

The trend of mean BMI values of US adults, birth cohorts 1882-1986 indicates that the obesity epidemic began earlier than hitherto thought

BACKGROUND

The trend in the body mass index (BMI) values of the US population has not been estimated accurately because the time series data are unavailable and the focus has been on calculating period effects.

OBJECTIVES

To estimate the trend and rate of change of BMI values by birth cohorts stratified by gender and ethnicity born 1882-1986.

METHODS

We use loess additive regression models to estimate age and trend effects of BMI values of US-born black and white adults measured between 1959 and 2006. We use all the National Health Examination Survey and National Health and Nutrition Examination Survey data.

RESULTS

The increase in BMI was already underway among the birth cohorts of the early 20th century. The rate of increase was fastest among black females; for the three other groups under consideration, the rates of increase were similar. The generally persistent upward trend was punctuated by upsurges, particularly after each of the two world wars. The estimated rate of change of BMI values increased by 71% among black females between the birth cohorts 1955 and those of 1965 is indicative of the rapid increases in their weight.

CONCLUSIONS

We infer that transition to postindustrial weights was a gradual process and began considerably earlier than hitherto supposed.

The relationship between physical work and the height premium: finnish evidence

This paper examines the role of physical strength in the determination of the height wage premium by using the "Health 2000 in Finland" data that contain both self-reported information on the physical strenuousness of work, and information on muscle mass from medical examinations. The results suggest that there are generally no distinct differences in the height premium between four different work strain categories. We also find that muscle mass is positively associated with wages per se. The premium is both statistically and economically more significant for men than for women. In terms of occupational sorting, we observe that the shortest men do physically very demanding work and the tallest do sedentary work, even after controlling for the influences of age and education.

Measures of the intergenerational transmission of body mass index between mothers and their children in the United States, 1981-2004

This research provides estimates of the intergenerational persistence of body mass index (BMI) between women and their children when both are at similar stages of the lifecycle. Using data from the National Longitudinal Survey of Youth 1979 (NLSY79) and the Young Adults of the NLSY79, associations between the weight status of women and their children are measured when both generations are between the ages of 16 and 24. In the entire sample, the measured intergenerational correlation of BMI is significantly different from zero and equal to 0.35. This result differs by gender with a BMI correlation between female children and their mothers of 0.38, compared to a significantly lower BMI correlation of 0.32 between mothers and their sons. Measures of this relationship across the distribution of BMI using quantile regression and quadrant dependence techniques indicate that the intergenerational persistence of BMI is strongest at higher levels of BMI. Strong dependence across generations is found when categorical outcomes of obesity and overweight are implemented. These results provide evidence of the strong persistence of weight problems across generations which may affect economic mobility within families.

Adding biomeasures relating to fatness and obesity to the Panel Study of Income Dynamics

The pace of research on the causes and consequences of obesity has increased dramatically since the late 1990s. However, a great chasm exists between the high-quality measurements of fatness used in the medical literature and the mostly self-reported height and weight data found in social science surveys. This article discusses the scientific value of including more accurate measures of fatness in the Panel Study of Income Dynamics (PSID). It describes why fatness and obesity are of interest to PSID users, the concepts they measure, the strengths and weaknesses of alternative biomeasures for these concepts, the value added of including each in the PSID, and their synergies with the PSID structure. Although no single measure of fatness is ideal for every situation, given scarce PSID resources we recommend adding waist circumference, percentage of body fat, total body fat, and fat free mass through a method such as bioelectrical impedance analysis, as well as determining genetic predisposition to obesity.