Bottoms up

Kevin Lewis

July 12, 2016

Does Banning Carbonated Beverages in Schools Decrease Student Consumption?

Shirlee Lichtman-Sadot

Journal of Public Economics, August 2016, Pages 30–50

I evaluate the effectiveness of carbonated beverage bans in schools by investigating their impact on household soda consumption. I match households in Nielsen Homescan Data to their school district’s carbonated beverage policies over an eight-year period (2002–2009). I find that when high schools ban the sale of carbonated beverages to students, households with a high school student experiencing the ban increase their consumption of non-diet soda by roughly the equivalent of 3.4 cans per month. I present evidence that this is a substantial offsetting (67–75%) of the average non-diet carbonated beverage consumption in high schools, when these are available to students, thus demonstrating the persistence of preferences when attempting to alter unhealthy habits.


The Impact of Late-Career Job Loss and Genotype on Body Mass Index

Lauren Schmitz & Dalton Conley

NBER Working Paper, June 2016

This study examines whether the effect of job loss on body mass index (BMI) at older ages is moderated by genotype using twenty years of socio-demographic and genome-wide data from the Health and Retirement Study (HRS). To avoid any potential confounding we interact layoffs due to a plant or business closure — a plausibly exogenous environmental exposure — with a polygenic risk score for BMI in a regression-adjusted semiparametric differences-in-differences matching framework that compares the BMI of those before and after an involuntary job loss with a control group that has not been laid off. Results indicate genetically-at-risk workers who lost their job before they were eligible for Social Security benefits, or before age 62, were more likely to gain weight. Further analysis reveals heterogeneous treatment effects by demographic, health, and socioeconomic characteristics. In particular, we find high risk individuals who gained weight after a job loss were more likely to be male, in worse health, single, and at the bottom half of the wealth distribution. Across the board, effects are concentrated among high-risk individuals who were not overweight prior to job loss, indicating unemployment at older ages may trigger weight gain in otherwise healthy or normal weight populations.


The impact of changing economic conditions on overweight risk among children in California from 2008 to 2012

Vanessa Oddo et al.

Journal of Epidemiology & Community Health, forthcoming

Methods: We investigated the association between indicators of changing macroeconomic conditions from 2008 to 2012 and overweight/obesity risk among school-aged children in California (n=1 741 712) using longitudinal anthropometric measurements. Multivariate regression, with individual and county fixed effects, was used to examine the effects of annual county-level unemployment and foreclosure rates on risk of child overweight/obesity, overall and among subgroups (race/ethnicity, sex, county-level median household income and county-level urban/rural status).

Results: From 2008 to 2012, ∼36% of children were overweight/obese and unemployment and foreclosure rates averaged 11% and 6.9%, respectively. A 1-percentage point (pp) increase in unemployment was associated with a 1.4 pp (95% CI 1.3 to 1.5) increase in overweight/obesity risk. Therefore, a child of average weight could expect a 14% increase in their body mass index z-score in association with a 1 pp increase in unemployment during the study period. We found some differences in the magnitude of the effects for unemployment among demographic subgroups, with the largest effects observed for unemployment among American Indians and Pacific Islanders.

Conclusions: Comparing children to themselves over time, we provide evidence that increases in county-level unemployment are associated with increased overweight/obesity risk. Given that overweight among children with lower economic resources remains a challenge for public health, these findings highlight the importance of policy-level approaches, which aim to mitigate the impact of decreased resources as economic conditions change.


The Changing Body Mass–Mortality Association in the United States: Evidence of Sex-Specific Cohort Trends from Three National Health and Nutrition Examination Surveys

Yan Yu

Biodemography and Social Biology, Summer 2016, Pages 143-163

The association between body mass index (BMI) categories and mortality remains uncertain. Using three National Health and Nutrition Examination Surveys covering the 1971–2006 period for cohorts born between 1896 and 1968, this study estimates separately for men and women models for year-of-birth (cohort) and year-of-observation (period) trends in how age-specific mortality rates differ across BMI categories. Among women, relative to the normal weight (BMI 18.5–24.9 kg/m2), there are increasing trends in mortality rates for the overweight (BMI 25–29.9) or obese (BMI ≥ 30). Among men, mortality rates relative to the normal weight decrease for the overweight, do not change for the moderately obese (BMI 30–34.9), and increase for the severely obese (BMI ≥ 35). Period and cohort trends are similar, but the cohort trends are more consistent. In the latest cohorts, compared with the normal weight, mortality rates are 50 percent lower for overweight men, not different for moderately obese men, and 100–200 percent higher for severely obese men and for overweight or obese women. For U.S. cohorts born after the 1920s, a lower overweight than normal weight mortality is confined to men. I speculate on possible reasons why the mortality association with overweight and obesity varies by sex and cohort.


The Effect of Sorority Membership on Eating Disorders, Body Weight, and Disordered-Eating Behaviors

Susan Averett, Sabrina Terrizzi & Yang Wang

Health Economics, forthcoming

Eating disorders are currently the deadliest mental disorder in the United States, affecting an estimated 12%–25% of all college women. Previous research has found a positive correlation between sorority membership and eating disorders, but the causal link has not been firmly established. We contribute to the literature by investigating a possible causal link among sororities and diagnosed eating disorders, measurable weight outcomes, and disordered-eating behaviors using data from the American College Health Association Survey. We handle the potential endogeneity of sorority membership using propensity score matching and instrumental variable methods to determine whether joining a sorority is a cause of the weight-related outcomes we study. We find that sorority members exhibit worse weight-related outcomes than those not in a sorority. However, our propensity score matching and instrumental variable results suggest that, other than BMI, this is merely a correlation, and there is little evidence that sorority membership is a cause of the outcomes we study.


Association Between Artificially Sweetened Beverage Consumption During Pregnancy and Infant Body Mass Index

Meghan Azad et al.

JAMA Pediatrics, July 2016, Pages 662-670

Design, Setting, and Participants: This cohort study included 3033 mother-infant dyads from the Canadian Healthy Infant Longitudinal Development (CHILD) Study, a population-based birth cohort that recruited healthy pregnant women from 2009 to 2012. Women completed dietary assessments during pregnancy, and their infants’ BMI was measured at 1 year of age (n = 2686; 89% follow-up). Statistical analysis for this study used data collected after the first year of follow-up, which was completed in October 2013. The data analysis was conducted in August 2015.

Results: The mean (SD) age of the 3033 pregnant women was 32.4 (4.7) years, and their mean (SD) BMI was 24.8 (5.4). The mean (SD) infant BMI z score at 1 year of age was 0.19 (1.05), and 5.1% of infants were overweight. More than a quarter of women (29.5%) consumed artificially sweetened beverages during pregnancy, including 5.1% who reported daily consumption. Compared with no consumption, daily consumption of artificially sweetened beverages was associated with a 0.20-unit increase in infant BMI z score (adjusted 95% CI, 0.02-0.38) and a 2-fold higher risk of infant overweight at 1 year of age (adjusted odds ratio, 2.19; 95% CI, 1.23-3.88). These effects were not explained by maternal BMI, diet quality, total energy intake, or other obesity risk factors. There were no comparable associations for sugar-sweetened beverages.

Conclusions and Relevance: To our knowledge, we provide the first human evidence that maternal consumption of artificial sweeteners during pregnancy may influence infant BMI. Given the current epidemic of childhood obesity and widespread use of artificial sweeteners, further research is warranted to confirm our findings and investigate the underlying biological mechanisms, with the ultimate goal of informing evidence-based dietary recommendations for pregnant women.


Desire for weight loss, weight-related social contact, and body mass outcomes

Matthew Andersson & Nicholas Christakis

Obesity, July 2016, Pages 1434–1437

Objective: This study evaluated whether desiring to lose weight is associated with subsequent changes in social contact with individuals perceived to be thinner or heavier.

Methods: Longitudinal data were used to examine associations between desiring to lose weight at baseline and social contact with thinner and heavier individuals across a 1-year follow-up period (N = 9,335, 2013–2014 Gallup National Panel). How baseline social contact is linked to body mass outcomes among those desiring to lose weight (N = 7,134) was also examined.

Results: Over time, individuals desiring to lose weight interacted more frequently (+69 interactions/year, on average) and were more likely to possess social ties (tie probability +0.12) with heavier individuals while lessening their interactions (−51 interactions/year) and decreasing their likelihood of ties (tie probability −0.048) with thinner individuals. On the other hand, increasing contacts and interactions with thinner individuals, and declining contacts and interactions with heavier individuals, were linked to actual weight loss.

Conclusions: Using national longitudinal data, an important mismatch was demonstrated between the social contacts created by individuals desiring weight loss and the contextual factors possibly useful for weight loss. This may help to explain why weight loss is often unsuccessful.


Heterogeneous Behavior, Obesity, and Storability in the Demand for Soft Drinks

Emily Wang, Christian Rojas & Francesca Colantuoni

American Journal of Agricultural Economics, forthcoming

We apply a dynamic estimation procedure to investigate the effect of obesity on the demand for soda. The dynamic model accounts for consumers’ storing behavior, and allows us to study soda consumers’ price sensitivity (how responsive consumers are to the overall price) and sale sensitivity (the fraction of consumers that store soda during temporary price reductions). By matching store-level purchase data to county-level data on obesity incidence, we find higher sale sensitivity in populations with higher obesity rates. Conversely, we find that storers are less price sensitive than non-storers, and that their price sensitivity decreases with the obesity rate. Our results suggest that policies aimed at increasing soda prices might be less effective than previously thought, especially in areas where consumers can counteract that price increase by stockpiling during sale periods; according to our results, this dampening effect would be more pronounced precisely in those areas with higher obesity rates.


Increased textural complexity in food enhances satiation

Danaé Larsen et al.

Appetite, October 2016, Pages 189–194

For the first time this study has shown a direct effect of food textural complexity on satiation. Independent of oral processing time, increasing the textural complexity of a food significantly decreased food intake. Foods with complex textures stimulate many sensory perceptions during oral processing, with a succession of textures perceived between first bite and swallow. Previously the impact of texture on satiation (commonly tested by increasing viscosities of semi-solids) has been explained by texture's influence on oral processing time; a long oral processing time enhances satiation. The results of the current study show that subjects in a randomised cross-over trial who consumed a “starter” (preload) model food with high textural complexity went on to eat significantly less of a two course ad libitum meal. Subjects who consumed a “starter” model food with low textural complexity, but with the same flavour, energy density and oral processing time, ate significantly more of the same ad libitum meal. The results show that increasing the number of textures perceived during chewing of a solid food triggers the satiation response earlier than when chewing a less texturally complex food. Increasing textural complexity of manufactured foods, to allow for greater sensory stimulation per bite, could potentially be used as a tool to enhance the satiation response and decrease food intake.


Toddlers’ bias to look at average versus obese figures relates to maternal anti-fat prejudice

Ted Ruffman et al.

Journal of Experimental Child Psychology, February 2016, Pages 195–202

Anti-fat prejudice (weight bias, obesity stigma) is strong, prevalent, and increasing in adults and is associated with negative outcomes for those with obesity. However, it is unknown how early in life this prejudice forms and the reasons for its development. We examined whether infants and toddlers might display an anti-fat bias and, if so, whether it was influenced by maternal anti-fat attitudes through a process of social learning. Mother–child dyads (N = 70) split into four age groups participated in a preferential looking paradigm whereby children were presented with 10 pairs of average and obese human figures in random order, and their viewing times (preferential looking) for the figures were measured. Mothers’ anti-fat prejudice and education were measured along with mothers’ and fathers’ body mass index (BMI) and children’s television viewing time. We found that older infants (M = 11 months) had a bias for looking at the obese figures, whereas older toddlers (M = 32 months) instead preferred looking at the average-sized figures. Furthermore, older toddlers’ preferential looking was correlated significantly with maternal anti-fat attitudes. Parental BMI, education, and children’s television viewing time were unrelated to preferential looking. Looking times might signal a precursor to explicit fat prejudice socialized via maternal anti-fat attitudes.


Marketing Vegetables in Elementary School Cafeterias to Increase Uptake

Andrew Hanks, David Just & Adam Brumberg

Pediatrics, forthcoming

Objectives: Children do not eat enough servings of vegetables, underscoring the need for effective interventions encouraging this behavior. The purpose of this research was to measure the impact that daily exposure to branded vegetable characters has on vegetable selection among boys and girls in elementary schools.

Methods: In a large urban school district, 10 elementary schools agreed to participate in the study. They were randomly assigned to a control condition or 1 of 3 treatment conditions: (1) a vinyl banner displaying vegetable characters that was fastened around the base of the salad bar; (2) short television segments with health education delivered by vegetable characters; or (3) a combination of the vinyl banner and television segments. We collected 22 206 student-day observations over a 6-week period by tallying the number of boys and girls taking vegetables from the school’s salad bar.

Results: Results show that 90.5% (from 12.6% to 24.0%; P = .04) more students took vegetables from the salad bar when exposed to the vinyl banner only, and 239.2% (from 10.2% to 34.6%; P < .001) more students visited the salad bar when exposed to both the television segments and vinyl banners. Both boys and girls responded positively to the vinyl banners (P < .05 in both cases).

Conclusions: Evidence from this study highlights the positive impact of branded media on children’s vegetable selection in the school cafeteria. Results from this study suggest potential opportunities for using branded media to encourage healthier choices for children.


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