Big and bigger

Kevin Lewis

August 27, 2017

Testing for Peer Effects Using Genetic Data
John Cawley et al.
NBER Working Paper, August 2017

Estimating peer effects is notoriously difficult because of the reflection problem and the endogeneity of peer group formation. This paper tests for peer effects in obesity in a novel way that addresses these challenges. It addresses the reflection problem by using the alter’s genetic risk score for obesity, which is a significant predictor of obesity, is determined prior to birth, and cannot be affected by the behavior of others. It addresses the endogeneity of peer group formation by examining peers who are not self-selected: full siblings. Using data from the National Longitudinal Survey of Adolescent Health, we find evidence of positive peer effects in weight and obesity; having a sibling with a high genetic predisposition raises one’s risk of obesity, even controlling for one’s own genetic predisposition to obesity. Implications of the findings include that peer effects may be an explanation for continued worldwide increases in weight, and that, because of social multipliers, the cost-effectiveness of obesity treatment and prevention programs may have been underestimated.

Implications of life-history strategies for obesity
Jon Maner et al.
Proceedings of the National Academy of Sciences, 8 August 2017, Pages 8517–8522

The association between low socioeconomic status (SES) and obesity is well documented. In the current research, a life history theory (LHT) framework provided an explanation for this association. Derived from evolutionary behavioral science, LHT emphasizes how variability in exposure to unpredictability during childhood gives rise to individual differences in a range of social psychological processes across the life course. Consistent with previous LHT research, the current findings suggest that exposure to unpredictability during childhood (a characteristic common to low SES environments) is associated with the adoption of a fast life-history strategy, one marked by impulsivity and a focus on short-term goals. We demonstrate that a fast life-history strategy, in turn, was associated with dysregulated weight-management behaviors (i.e., eating even in the absence of hunger), which were predictive of having a high body mass index (BMI) and being obese. In both studies, findings held while controlling for participants’ current socioeconomic status, suggesting that obesity is rooted in childhood experiences. A serial mediation model in study 2 confirmed that effects of childhood SES on adult BMI and obesity can be explained in part by exposure to unpredictability, the adoption of a fast life-history strategy, and dysregulated-eating behaviors. These findings suggest that weight problems in adulthood may be rooted partially in early childhood exposure to unpredictable events and environments. LHT provides a valuable explanatory framework for understanding the root causes of obesity.

The Impact of Crowding on Calorie Consumption
Stefan Hock & Rajesh Bagchi
Journal of Consumer Research, forthcoming

Consumer behavior is often influenced by subtle environmental cues, such as temperature, color, lighting, scent or sound. We explore the effects of a not-so-subtle cue — human crowding — on calorie consumption. Although crowding is an omnipresent factor, it has received little attention in the marketing literature. We present six studies showing that crowding increases calorie consumption. These effects occur because crowding increases distraction, which hampers cognitive thinking and evokes more affective processing. When consumers process information affectively, they consume more calories. We show the specific reason for the increase in calories. When given a choice between several different options, people select and eat higher-calorie items, but when presented with only one option, people eat more of the same food item. We document this process, rule out alternative explanations, and discuss theoretical and managerial implications.

Partisan Responses to Public Health Messages: Motivated Reasoning and Sugary Drink Taxes
Sarah Gollust, Colleen Barry & Jeff Niederdeppe
Journal of Health Politics, Policy and Law, forthcoming

This study examines the public's motivated reasoning of competitive messages about sugary drink taxes, a public health policy approach attempted with some recent success in the United States. In an experiment embedded in a nationally representative survey fielded in the fall of 2012, we randomized participants (N = 5,147) to receive one of four messages: control, a strong protax message, a two-sided message, or a message refuting arguments made in soda company antitax messages. The protax message showed no effects on tax support, while the two-sided message depressed Republicans' support. The refutation message boosted independents' support but produced backlash among Republicans. This motivated response was pronounced among Republicans who were plausibly previously exposed to the sugary drink tax debate. These findings reinforce the communication challenges in an increasingly politicized US health policy discourse.

The Medical Care Costs of Youth Obesity: An Instrumental Variables Approach
Adam Biener, John Cawley & Chad Meyerhoefer
NBER Working Paper, August 2017

This paper is the first to use the method of instrumental variables to estimate the causal impact of youth obesity on U.S. medical care costs. We examine data from the Medical Expenditure Panel Survey for 2001-2013 and instrument for child BMI using the BMI of the child’s biological mother. IV estimates indicate that obesity raises annual medical care costs by $1,354 (in 2013 dollars) or 159%, which is considerably higher than previous estimates of the association of youth obesity with medical costs; thus, the cost-effectiveness of anti-obesity interventions have likely been underestimated. The costs of youth obesity are borne almost entirely by third party-payers, which is consistent with substantial externalities of youth obesity, which in turn represents an economic rationale for government intervention.

Geographic Accessibility Of Food Outlets Not Associated With Body Mass Index Change Among Veterans, 2009–14
Shannon Zenk et al.
Health Affairs, August 2017, Pages 1433-1442

In recent years, various levels of government in the United States have adopted or discussed subsidies, tax breaks, zoning laws, and other public policies that promote geographic access to healthy food. However, there is little evidence from large-scale longitudinal or quasi-experimental research to suggest that the local mix of food outlets actually affects body mass index (BMI). We used a longitudinal design to examine whether the proximity of food outlets, by type, was associated with BMI changes between 2009 and 2014 among 1.7 million veterans in 382 metropolitan areas. We found no evidence that either absolute or relative geographic accessibility of supermarkets, fast-food restaurants, or mass merchandisers was associated with changes in an individual’s BMI over time. While policies that alter only geographic access to food outlets may promote equitable access to healthy food and improve nutrition, our findings suggest they will do little to combat obesity in adults.

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