Weighted
Jay Bhattacharya & Neeraj Sood
Journal of Economic Perspectives, Winter 2011, Pages 139-158
Abstract:
Adult obesity is a growing problem. From 1962 to 2006, obesity prevalence nearly tripled to 35.1 percent of adults. The rising prevalence of obesity is not limited to a particular socioeconomic group and is not unique to the United States. Should this widespread obesity epidemic be a cause for alarm? From a personal health perspective, the answer is an emphatic "yes." But when it comes to justifications of public policy for reducing obesity, the analysis becomes more complex. A common starting point is the assertion that those who are obese impose higher health costs on the rest of the population-a statement which is then taken to justify public policy interventions. But the question of who pays for obesity is an empirical one, and it involves analysis of how obese people fare in labor markets and health insurance markets. We will argue that the existing literature on these topics suggests that obese people on average do bear the costs and benefits of their eating and exercise habits. We begin by estimating the lifetime costs of obesity. We then discuss the extent to which private health insurance pools together obese and thin, whether health insurance causes obesity, and whether being fat might actually cause positive externalities for those who are not obese. If public policy to reduce obesity is not justified on the grounds of external costs imposed on others, then the remaining potential justification would need to be on the basis of helping people to address problems of ignorance or self-control that lead to obesity. In the conclusion, we offer a few thoughts about some complexities of such a justification.
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Could increased time spent in a thermal comfort zone contribute to population increases in obesity?
F. Johnson, A. Mavroggiani, M. Ucci, A. Vidal-Puig & J. Wardle
Obesity Reviews, forthcoming
Abstract:
Domestic winter indoor temperatures in the USA, UK and other developed countries appear to be following an upwards trend. This review examines evidence of a causal link between thermal exposures and increases in obesity prevalence, focusing on acute and longer-term biological effects of time spent in thermal comfort compared with mild cold. Reduced exposure to seasonal cold may have a dual effect on energy expenditure, both minimizing the need for physiological thermogenesis and reducing thermogenic capacity. Experimental studies show a graded association between acute mild cold and human energy expenditure over the range of temperatures relevant to indoor heating trends. Meanwhile, recent studies of the role of brown adipose tissue (BAT) in human thermogenesis suggest that increased time spent in conditions of thermal comfort can lead to a loss of BAT and reduced thermogenic capacity. Pathways linking cold exposure and adiposity have not been directly tested in humans. Research in naturalistic and experimental settings is needed to establish effects of changes in thermal exposures on weight, which may raise possibilities for novel public health strategies to address obesity.
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The role of automatic obesity stereotypes in real hiring discrimination
Jens Agerström & Dan-Olof Rooth
Journal of Applied Psychology, forthcoming
Abstract:
This study examined whether automatic stereotypes captured by the implicit association test (IAT) can predict real hiring discrimination against the obese. In an unobtrusive field experiment, job applications were sent to a large number of real job vacancies. The applications were matched on credentials but differed with respect to the applicant's weight. Discriminatory behavior was quantified by the extent to which the hiring managers invited normal-weight versus obese applicants to a job interview. Several months after the behavioral data were obtained, the hiring managers completed an obesity IAT and explicit hiring preference measures. Only the IAT scores reliably predicted interview decisions. More specifically, hiring managers holding more negative automatic stereotypes about the obese were less likely to invite an obese applicant for an interview. The present research is the first to show that automatic bias predicts labor market discrimination against obese individuals. Practical implications are discussed.
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Overweight Adults May Have the Lowest Mortality - Do They Have the Best Health?
Anna Zajacova, Jennifer Beam Dowd & Sarah Burgard
American Journal of Epidemiology, 15 February 2011, Pages 430-437
Abstract:
Numerous recent studies have found that overweight adults experience lower overall mortality than those who are underweight, normal-weight, or obese. These highly publicized findings imply that overweight may be the optimal weight category for overall health via its association with longevity-a conclusion with important public health implications. In this study, the authors examined the association between body mass index (BMI; (weight (kg)/height (m)2)) and 3 markers of health risks using a nationally representative sample of US adults aged 20-80 years (n = 9,255) from the National Health and Nutrition Examination Survey (2005-2008). Generalized additive models, a type of semiparametric regression model, were used to examine the relations between BMI and biomarkers of inflammation, metabolic function, and cardiovascular function (C-reactive protein, hemoglobin A1c, and high density lipoprotein cholesterol, respectively). The association between BMI and each biomarker was monotonic, with higher BMI being consistently associated with worse health risk profiles at all ages, in contrast to the U-shaped relation between BMI and mortality. Prior results suggesting that the overweight BMI category corresponds to the lowest risk of mortality may not be generalizable to indicators of health risk.
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Catherine Davis et al.
Health Psychology, January 2011, Pages 91-98
Objective: This experiment tested the hypothesis that exercise would improve executive function.
Design: Sedentary, overweight 7- to 11-year-old children (N = 171, 56% girls, 61% Black, M ± SD age = 9.3 ± 1.0 years, body mass index [BMI] = 26 ± 4.6 kg/m², BMI z-score = 2.1 ± 0.4) were randomized to 13 ± 1.6 weeks of an exercise program (20 or 40 min/day), or a control condition.
Main Outcome Measures: Blinded, standardized psychological evaluations (Cognitive Assessment System and Woodcock-Johnson Tests of Achievement III) assessed cognition and academic achievement. Functional MRI measured brain activity during executive function tasks.
Results: Intent to treat analysis revealed dose-response benefits of exercise on executive function and mathematics achievement. Preliminary evidence of increased bilateral prefrontal cortex activity and reduced bilateral posterior parietal cortex activity attributable to exercise was also observed.
Conclusion: Consistent with results obtained in older adults, a specific improvement on executive function and brain activation changes attributable to exercise were observed. The cognitive and achievement results add evidence of dose-response and extend experimental evidence into childhood. This study provides information on an educational outcome. Besides its importance for maintaining weight and reducing health risks during a childhood obesity epidemic, physical activity may prove to be a simple, important method of enhancing aspects of children's mental functioning that are central to cognitive development. This information may persuade educators to implement vigorous physical activity.
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Maximilian Schmeiser
Health Economics, forthcoming
Abstract:
Participation in the Supplemental Nutrition Assistance Program (SNAP) reached an all-time high of 40.2 million persons in March 2010, which means the program affects a substantial fraction of Americans. A significant body of research has emerged suggesting that participation in SNAP increases the probability of being obese for adult women and has little effect on the probability for adult men. However, studies addressing the effects of participation on children have produced mixed results. This paper examines the effect of long-term SNAP participation on the Body Mass Index (BMI) percentile and probability of being overweight or obese for children ages 5-18 using data from the National Longitudinal Survey of Youth 1979 Children and Young Adults data set. An instrumental variables identification strategy that exploits exogenous variation in state-level program parameters, as well as state and federal expansions of the Earned Income Tax Credit (EITC), is used to address the endogeneity between SNAP participation and obesity. SNAP participation is found to significantly reduce BMI percentile and the probability of being overweight or obese for boys and girls ages 5-11 and boys ages 12-18. For girls ages 12-18, SNAP participation appears to have no significant effect on these outcomes.
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Effect of food prices on the prevalence of obesity among young adults
E. Han & L.M. Powell
Public Health, forthcoming
Objective: To examine the extent to which various food prices were associated with the obesity status of young adults.
Study design: Retrospective cohort study of 6537 men and 5324 women in the USA using panel data from the Monitoring the Future Surveys (1992-2003), which were merged with two food-at-home and one food-away-from-home price measures from the American Chamber of Commerce Researchers Association.
Methods: Longitudinal individual random effect and fixed effect models were estimated.
Results: This study found that food prices did not have a significant effect on the prevalence of obesity among young female adults. For young adult men, an individual random effect estimator suggested that a 10% increase in the price of fast food was associated with a 13.2% decrease in the probability of obesity, but this effect lost its economic and statistical significance once individual fixed effects were controlled for in the estimation.
Conclusions: Overall, the results imply that observed time-varying individual characteristics, such as working status, marital status and school enrolment status, may over-ride the effect of changes in food prices for young adults. More research employing longitudinal data is necessary to determine if food subsidies or taxes, particularly soft drink and fast food taxes or subsidies for fruit and vegetables, could be effective policy measures to curtail the increasing prevalence of obesity among young adults.
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The invisible benefits of exercise
Matthew Ruby et al.
Health Psychology, January 2011, Pages 67-74
Objective: To examine whether - and why - people underestimate how much they enjoy exercise.
Design: Across four studies, 279 adults predicted how much they would enjoy exercising, or reported their actual feelings after exercising.
Main Outcome Measures: Main outcome measures were predicted and actual enjoyment ratings of exercise routines, as well as intention to exercise.
Results: Participants significantly underestimated how much they would enjoy exercising; this affective forecasting bias emerged consistently for group and individual exercise, and moderate and challenging workouts spanning a wide range of forms, from yoga and Pilates to aerobic exercise and weight training (Studies 1 and 2). We argue that this bias stems largely from forecasting myopia, whereby people place disproportionate weight on the beginning of a workout, which is typically unpleasant. We demonstrate that forecasting myopia can be harnessed (Study 3) or overcome (Study 4), thereby increasing expected enjoyment of exercise. Finally, Study 4 provides evidence for a mediational model, in which improving people's expected enjoyment of exercise leads to increased intention to exercise.
Conclusion: People underestimate how much they enjoy exercise because of a myopic focus on the unpleasant beginning of exercise, but this tendency can be harnessed or overcome, potentially increasing intention to exercise.
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Emotional eating: Eating when emotional or emotional about eating?
Marieke Adriaanse, Denise de Ridder & Catharine Evers
Psychology & Health, January 2011, Pages 23-39
Abstract:
This article examines the extent to which self-reported emotional eating is a predictor of unhealthy snack consumption or, alternatively, an expression of beliefs about the relation between emotions and eating derived from concerns about eating behaviour. Three studies were conducted. Study 1 (N = 151) and Study 2 (N = 184) investigated the predictive validity of emotional eating compared to habit strength in snack consumption, employing 7-day snack diaries. Both studies demonstrated that snack consumption was not predicted by emotional eating but depended on the habit of unhealthy snacking and on restraint eating. As emotional eating was not a significant predictor of snack intake, Study 3 addressed the alternative hypothesis of emotional eating being an expression of concerns about eating behaviour. Results from this cross-sectional survey (N = 134) showed that emotional eating was significantly associated with several concerns. Together, these studies show that snack intake is better predicted by habit strength and restraint eating than by emotional eating. Additionally, the results suggest that in normal-weight women the concept of emotional eating may not capture the tendency to eat under emotional conditions, but rather reflects beliefs about the relation between emotions and eating.
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Child and adolescent fast-food choice and the influence of calorie labeling: A natural experiment
B. Elbel, J. Gyamfi & R. Kersh
International Journal of Obesity, forthcoming
Objective: Obesity is an enormous public health problem and children have been particularly highlighted for intervention. Of notable concern is the fast-food consumption of children . However, we know very little about how children or their parents make fast-food choices, including how they respond to mandatory calorie labeling. We examined children's and adolescents' fast-food choice and the influence of calorie labels in low-income communities in New York City (NYC) and in a comparison city (Newark, NJ).
Design: Natural experiment: Survey and receipt data were collected from low-income areas in NYC, and Newark, NJ (as a comparison city), before and after mandatory labeling began in NYC. Study restaurants included four of the largest chains located in NYC and Newark: McDonald's, Burger King, Wendy's and Kentucky Fried Chicken.
Subjects: A total of 349 children and adolescents aged 1-17 years who visited the restaurants with their parents (69%) or alone (31%) before or after labeling was introduced. In total, 90% were from racial or ethnic minority groups.
Results: We found no statistically significant differences in calories purchased before and after labeling; many adolescents reported noticing calorie labels after their introduction (57% in NYC) and a few considered the information when ordering (9%). Approximately 35% of adolescents ate fast food six or more times per week and 72% of adolescents reported that taste was the most important factor in their meal selection. Adolescents in our sample reported that parents have some influence on their meal selection.
Conclusions: Adolescents in low-income communities notice calorie information at similar rates as adults, although they report being slightly less responsive to it than adults. We did not find evidence that labeling influenced adolescent food choice or parental food choices for children in this population.
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Maternal Employment, Work Schedules, and Children's Body Mass Index
Taryn Morrissey, Rachel Dunifon & Ariel Kalil
Child Development, January/February 2011, Pages 66-81
Abstract:
Previous work has shown that mothers' employment is associated with increases in children's body mass index (BMI), a measure of weight for height. Nonstandard work (working evenings or nights, weekends, or an irregular shift) may also be associated with children's BMI. This article examines the association between maternal work and children's BMI and considers the influence of mothers' nonstandard work schedules. Using data from school-age children (approximately 8 to 12 years) in the NICHD's Study of Early Child Care and Youth Development (N = 990), this study found that an increase in the total time a mother is employed is associated with an increase in her child's BMI; additionally, the association between maternal employment and children's weight is much stronger at 6th grade relative to younger ages. There was no evidence that maternal or home characteristics or children's time use mediated these associations, nor was there any evidence that nonstandard work was associated with children's BMI. Implications for policy and future research are discussed.
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R.D. Mattes, J.M. Shikany, K.A. Kaiser & D.B. Allison
Obesity Reviews, forthcoming
Abstract:
Nutritively sweetened beverages (NSBs) may play a role in the obesity epidemic. We abstracted data from randomized controlled trials (RCTs) and evidence-based reviews through January 2009 concerning effects of consumption of NSBs on changes in body weight and adiposity. Studies included were those (i) conducted in humans; (ii) lasting at least 3 weeks; (iii) incorporating random assignment of subjects to conditions that differed only in the consumption of NSBs and (iv) including an adiposity indicator as an outcome. Twelve studies met the inclusion criteria. Meta-analysis of six studies that added NSBs to persons' diets showed dose-dependent increases in weight. Contrarily, meta-analysis of studies that attempted to reduce NSB consumption consistently showed no effect on body mass index (BMI) when all subjects were considered. Meta-analysis of studies providing access to results separately for subjects overweight at baseline showed a significant effect of a roughly 0.35 standard deviations lesser BMI change (i.e. more weight loss or less weight gain) relative to controls. The current evidence does not demonstrate conclusively that NSB consumption has uniquely contributed to obesity or that reducing NSB consumption will reduce BMI levels in general. We recommend an adequately powered RCT with overweight persons, for whom there is suggestive evidence of an effect.
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Céline Bonnet & Vincent Requillart
Health Economics, forthcoming
Abstract:
Whereas National Health authorities recommend a decrease in the consumption of ‘added' sugar, a reform on the sugar market will lead to a 36% decrease of the sugar price in the EU. Using French data on soft drinks purchases, this paper investigates the anticipated impact of this reform on the consumption of sugar-sweetened beverages. The reform of the EU sugar policy leads to a decrease in regular soft drink prices by 3% and varies across brands. To assess substitution within this food category, we use a random-coefficients logit model that takes into account a large number of differentiated products and heterogeneity in consumers' behavior. Results suggest that price changes would lead to an increase in market shares of regular products by 7.5% and to substitutions between brands to the benefit of products with the highest sugar content. On the whole, it would raise consumption of regular soft drinks by more than 1 litre per person per year and consumption of added sugar by 124 g per person per year, this increase being larger in households composed of overweight and obese individuals.
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"Guys, She's Humongous!": Gender and Weight-Based Teasing in Adolescence
Nicole Taylor
Journal of Adolescent Research, March 2011, Pages 178-199
Abstract:
Ethnographic research, including individual interviews, focus groups, and participant observation, was conducted to examine how adolescents defined and negotiated the boundaries between normal/acceptable weight and overweight through direct and indirect teasing. In particular, this article focuses on gender differences in weight-based teasing and in the ways boys and girls responded to being teased within the high school context. Findings suggest that girls' body fat was more closely monitored and criticized than boys' by both male and female peers. Boys and girls of all sizes and all social groups, including teens who were overweight, were critical of people who displayed body fat. This article argues that by engaging in "othering" discourses of their peers' body fat, adolescents, regardless of their size, were able to discursively construct themselves as "normal" in comparison. In doing so, they negotiated a higher social rank for themselves and distanced themselves from the reality of everyday fatness.
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Environmental Influences on Young Adult Weight Gain: Evidence From a Natural Experiment
Kandice Kapinos & Olga Yakusheva
Journal of Adolescent Health, January 2011, Pages 52-58
Objectives: This study investigated the importance of environmental influences in explaining weight gain and related behaviors among freshman college students.
Methods: We exploited a natural experiment that takes place on most college campuses in the United States - randomized dormitory assignments. We estimated the effects of living in dormitories with varying physical environment characteristics on weight gain and related behaviors (daily number of meals and snacks, weekly frequency of exercise) among randomly assigned freshman students.
Results: We found strong evidence linking weight and related behaviors to individual dormitories, as well as to specific characteristics of the dormitories. On average, students assigned to dormitories with on-site dining halls gained more weight and exhibited more behaviors consistent with weight gain during the freshman year as compared with students not assigned to such dormitories. Females in such dormitories weighed .85 kg (p = .03) more and exercised 1.43 (p < .01) times fewer; males consumed .22 (p = .02) more meals and .38 (p = .01) more snacks. For female students, closer proximity of the dormitory to a campus gym led to more frequent exercise (.54, p = .03), whereas living closer to central campus reduced exercise (-.97, p = .01).
Conclusions: Using a natural experiment to deal with the potential endogeneity of the living environment, this study found that the physical environment affects both students' weight changes and weight-related behaviors.
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Is Body Mass Index in Old Age Related to Cognitive Abilities? The Lothian Birth Cohort 1936 Study
Janie Corley, Alan Gow, John Starr & Ian Deary
Psychology and Aging, December 2010, Pages 867-875
Abstract:
We tested the hypothesis that the previously reported association between a higher body mass index (BMI) and poorer cognition in later adulthood is an artifact of confounding by previous cognitive ability and socioeconomic status. Participants were 1,079 adults aged about 70 years in the Lothian Birth Cohort 1936 Study, on whom there are IQ data from age 11. Cognitive outcome measures included: IQ at age 70 using the same test that was administered at age 11; composite measures of general cognitive ability (g factor), speed of information processing, and memory; and two tests of verbal ability. People classified as overweight or obese in later adulthood had significantly lower scores on tests of childhood IQ, age 70 IQ, g factor, and verbal ability. There was no significant association with processing speed or memory performance. After adjusting for childhood IQ and social class in general linear models, associations with age 70 IQ and g factor were nonsignificant or attenuated. However, throughout the models, there was a persistent (inverse) relationship between BMI and performance on the National Adult Reading Test (NART) and Wechsler Test of Adult Reading (WTAR), which remained significant after full adjustment for all sociodemographic and health covariates (for the NART, p = .025; for the WTAR, p = .011). The findings suggest that the previously reported BMI-cognition associations in later adulthood could be largely accounted for by prior ability and socioeconomic status, and by the possible influence of these factors on the adoption of health behaviors in adulthood.
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Race and gender differences in the cognitive effects of childhood overweight
Susan Averett & David Stifel
Applied Economics Letters, November 2010, Pages 1673-1679
Abstract:
The increase in the prevalence of overweight children (ages 6-13 years) in the United States over the past two decades is likely to result in adverse public health consequences. We use data from the children of the National Longitudinal Survey of Youth 1979 cohort to investigate an additional consequence of childhood overweight - its effect on relative cognitive development. To control for unobserved heterogeneity, we estimate individual (child) fixed effect (FE) models and instrumental variable (IV) models. Although recent research suggests that there is a negligible effect of childhood overweight on cognitive ability, our results demonstrate that the effects are uncovered when examining the relationship separately by race. In particular, we find that overweight white boys have math and reading scores approximately an SD lower than the mean. Overweight white girls have lower math scores whereas overweight black boys and girls have lower reading scores. Our results suggest that in addition to well-documented health consequences, overweight children may also be at risk in terms of experiencing adverse education outcomes, which could lead to lower future wages.
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Kate Northstone et al.
Journal of Epidemiology and Community Health, forthcoming
Background: Little is known about the effects of overall diet in childhood and intelligence later in life.
Methods: The current study, based on the Avon Longitudinal Study of Parents and Children, uses data on children's diet reported by parents in food-frequency questionnaires at 3, 4, 7 and 8.5 years of age. Dietary patterns were identified using principal-components analysis and scores computed at each age. IQ was assessed using the Wechsler Intelligence Scale for Children at 8.5 years. Data on a number of confounders were collected, and complete data were available for 3966 children.
Results: After adjustment, the ‘processed' (high fat and sugar content) pattern of diet at 3 years of age was negatively associated with IQ assessed at 8.5 years of age-a 1 SD increase in dietary pattern score was associated with a 1.67 point decrease in IQ (95% CI -2.34 to -1.00; p<0.0001). The ‘health-conscious' (salad, rice, pasta, fish, fruit) pattern at 8.5 years was positively associated with IQ: a 1 SD increase in pattern score led to a 1.20 point increase in IQ (95% CI 0.52 to 1.88; p=0.001).
Conclusion: There is evidence that a poor diet associated with high fat, sugar and processed food content in early childhood may be associated with small reductions in IQ in later childhood, while a healthy diet, associated with high intakes of nutrient rich foods described at about the time of IQ assessment may be associated with small increases in IQ.
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D.-X. Tan, L.C. Manchester, L. Fuentes-Broto, S.D. Paredes & R.J. Reiter
Obesity Reviews, forthcoming
Abstract:
A worldwide increase in the incidence of obesity indicates the unsuccessful battle against this disorder. Obesity and the associated health problems urgently require effective strategies of treatment. The new discovery that a substantial amount of functional brown adipose tissue (BAT) is retained in adult humans provides a potential target for treatment of human obesity. BAT is active metabolically and disposes of extra energy via generation of heat through uncoupling oxidative phosphorylation in mitochondria. The physiology of BAT is readily regulated by melatonin, which not only increases recruitment of brown adipocytes but also elevates their metabolic activity in mammals. It is speculated that the hypertrophic effect and functional activation of BAT induced by melatonin may likely apply to the human. Thus, melatonin, a naturally occurring substance with no reported toxicity, may serve as a novel approach for treatment of obesity. Conversely, because of the availability of artificial light sources, excessive light exposure after darkness onset in modern societies should be considered a potential contributory factor to human obesity as light at night dramatically reduces endogenous melatonin production. In the current article, the potential associations of melatonin, BAT, obesity and the medical implications are discussed.