Big issues

Kevin Lewis

May 24, 2016

Obesity and sex ratios in the U.S.

Wanchuan Lin, Kathryn McEvilly & Juan Pantano

Review of Economics of the Household, June 2016, Pages 269-292

This paper studies how rising male incarceration and its impact on marriage markets has affected female incentives to gain weight. Exogenous variation in marriage market conditions is obtained from differential trends in male incarceration rates across markets defined by race, location and age. We provide evidence that marriage market conditions do in fact affect the incidence of obesity. In particular, we find that increases in male imprisonment that reduced the male–female sex-ratio explain about 18 % of the increase in the female obesity rate for African-Americans in the United States over the 1990s. Results are particularly large for those in the younger age group (ages 18–23).


Shining Light on Atmospherics: How Ambient Light Influences Food Choices

Dipayan Biswas et al.

Journal of Marketing Research, forthcoming

Retail atmospherics is emerging as a major competitive tool, and it is especially notable in the restaurant industry where lighting is used to create the overall ambience and influence consumer experience. Along with influencing overall experience, can ambient light luminance have unintended consequences in terms of influencing what a diner orders? The results of a field study at multiple locations of a major restaurant chain and a series of lab studies robustly show that consumers tend to choose less healthy food options when ambient lighting is dim (vs. bright). Process evidence suggests that this phenomenon occurs because ambient light luminance influences mental alertness, which in turn influences food choices. While restaurant and perhaps grocery store managers can use these insights and their ambient light switches to nudge consumers toward targeted food choices, such as healthy or high margin signature items, health conscious consumers can opt for dining environments with bright ambient lighting.


Prevalence of obesity and severe obesity in US children, 1999-2014

Asheley Cockrell Skinner, Eliana Perrin & Joseph Skelton

Obesity, May 2016, Pages 1116–1123

Objective: Provide the most recent data on the prevalence of obesity and severe obesity among United States children and adolescents aged 2 to 19 years.

Methods: The National Health and Nutrition Examination Survey, 1999–2014, was used. Weight status was defined using measured height and weight and standard definitions as follows: overweight as ≥85th percentile for age- and sex-specific BMI; class I obesity as ≥95th percentile; class II obesity as ≥120 of the 95th percentile, or BMI ≥35; and class III obesity as ≥140% of the 95th percentile, or BMI ≥40. This study reports the prevalence of obesity by 2-year National Health and Nutrition Examination Survey cycle and Wald tests comparing the 2011–2012 cycle with the 2013–2014 cycle, as well as the linear trend from 1999 to 2014. Multivariable logistic regression models estimated odds ratios for differences by each 2-year cycle.

Results: In 2013–2014, 17.4% of children met criteria for class I obesity, including 6.3% for class II and 2.4% for class III, none statistically different than 2011–2012. A clear, statistically significant increase in all classes of obesity continued from 1999 through 2014.

Conclusions: There is no evidence of a decline in obesity prevalence in any age group, despite substantial clinical and policy efforts targeting the issue.


Why can't we control our food intake? The downside of dietary variety on learned satiety responses

Ashley Martin

Physiology & Behavior, forthcoming

A striking feature of the modern food environment is the sheer amount of dietary choice available to the individual. In addition to an endless variety of highly palatable and energy dense foods, efforts to combat obesity have resulted in the production of several low- and reduced-calorie versions of these foods that are marketed to consumers. As a result, we are now confronted with a staggering amount of ‘dietary variability’ — the same food item can be obtained in a variety of different energy densities. This is a concern because evidence in rodents suggests that this kind of dietary variability can compromise one of the major cognitive determinants of food intake among non-human animals — flavor-nutrient satiety learning. Flavor-nutrient satiety learning enables animals to learn about the energy content or satiating quality of the foods they consume and adjust their intake to fit their energy needs. Notably, evidence suggests that dietary variability can disrupt this kind of learning, leading to overeating and weight gain. Here, we discuss the utility of flavor-nutrient satiety learning in human dietary behavior, highlighting certain features of the modern environment that can be disruptive to the acquisition of this kind of learning in humans. Special emphasis is placed on dietary variability, however we will also highlight other aspects of the environment that can undermine this kind of learning, such as competition from other satiety-relevant cues (i.e., food labels), detrimental effects of Western diets on food-related cognitive processing, and the abundance of macronutrients that are inadequate at supporting learned satiety responses. The goal of this work is to highlight novel ways in which the environment may disrupt food-relevant learning and energy intake, and to provide some explanation for the elusive nature of flavor-nutrient learning in humans.


Neighborhood and Home Food Environment and Children’s Diet and Obesity: Evidence from Military Personnel’s Installation Assignment

Victoria Shier, Nancy Nicosia & Ashlesha Datar

Social Science & Medicine, June 2016, Pages 122–131

Research and policy initiatives are increasingly focused on the role of neighborhood food environment in children’s diet and obesity. However, existing evidence relies on observational data that is limited by neighborhood selection bias. The Military Teenagers’ Environments, Exercise, and Nutrition Study (M-TEENS) leverages the quasi-random variation in neighborhood environment generated by military personnel’s assignment to installations to examine whether neighborhood food environments are associated with children’s dietary behaviors and BMI. Our results suggest that neither the actual nor the perceived availability of particular food outlets in the neighborhood is associated with children’s diet or BMI. The availability of supermarkets and convenience stores in the neighborhood was not associated with where families shop for food or children’s dietary behaviors. Further, the type of store that families shop at was not associated with the healthiness of food available at home. Similarly, availability of fast food and restaurants was unrelated to children’s dietary behaviors or how often children eat fast food or restaurant meals. However, the healthiness of food available at home was associated with healthy dietary behaviors while eating at fast food outlets and restaurants were associated with unhealthy dietary behaviors in children. Further, parental supervision, including limits on snack foods and meals eaten as a family, was associated with dietary behaviors. These findings suggest that focusing only on the neighborhood food environment may ignore important factors that influence children’s outcomes. Future research should also consider how families make decisions about what foods to purchase, where to shop for foods and eating out, how closely to monitor their children’s food intake, and, ultimately how these decisions collectively impact children’s outcomes.


Food Environments and Obesity: Household Diet Expenditure Versus Food Deserts

Danhong Chen, Edward Jaenicke & Richard Volpe

American Journal of Public Health, May 2016, Pages 881-888

Objectives: To examine the associations between obesity and multiple aspects of the food environments, at home and in the neighborhood.

Methods: Our study included 38 650 individuals nested in 18 381 households located in 2104 US counties. Our novel home food environment measure, USDAScore, evaluated the adherence of a household’s monthly expenditure shares of 24 aggregated food categories to the recommended values based on US Department of Agriculture food plans. The US Census Bureau’s County Business Patterns (2008), the detailed food purchase information in the IRi Consumer Panel scanner data (2008–2012), and its associated MedProfiler data set (2012) constituted the main sources for neighborhood-, household-, and individual-level data, respectively.

Results: After we controlled for a number of confounders at the individual, household, and neighborhood levels, USDAScore was negatively linked with obesity status, and a census tract–level indicator of food desert status was positively associated with obesity status.

Conclusions: Neighborhood food environment factors, such as food desert status, were associated with obesity status even after we controlled for home food environment factors.


Why has the prevalence of obesity doubled?

Charles Baum & Shin-Yi Chou

Review of Economics of the Household, June 2016, Pages 251-267

The prevalence of obesity has doubled over the last 25 years. We estimate the effects of multiple socio-environmental factors (e.g., physical demands at work, restaurants, food prices, cigarette smoking, food stamps, and urban sprawl) on obesity using NLSY data. Then we use the Oaxaca–Blinder decomposition technique to approximate the contribution of each socio-environmental factor to the increase during this time. Many socio-environmental factors significantly affect weight, but none are able to explain a large portion of the obesity increase. Decreases in cigarette smoking consistently explains about 2–4 % of the increase in obesity and BMI. Food stamp receipt also consistently affects the measures of weight, but the small decrease in food stamp program participation during the period we examine actually dampened the increases in obesity and BMI. Collectively, the socio-environmental factors we examine never explain more than about 6.5 % of the weight increases.


Psychosocial factors as mediators of food Insecurity and weight status among middle school students

Don Willis & Kevin Fitzpatrick

Appetite, August 2016, Pages 236–243

Research regarding the association between food insecurity and weight status among youth has produced mixed results. However, few studies on this topic have utilized data that includes survey responses from children themselves regarding their experience with food insecurity. This study was undertaken to examine the association between food insecurity and weight status among youth, as well as the potential mediation by psychosocial factors. A survey of 5th-7th grade students was administered to gather information on food insecurity, social and psychological resources, and health. The primary analysis includes OLS (Ordinary Least Squares) regression conducted using SPSS software and Sobel's test for mediation. Results suggest a positive association between food insecurity and weight status even when controlling for key demographic variables. In addition, we find that this association is mediated by psychosocial factors — namely, perceived social status and depression. Insights from this work highlight the need to consider non-nutritional pathways through which food insecurity impacts health as well the need to continue surveying youth directly when examining their experiences with food insecurity.


More Similar but Less Satisfying: Comparing Preferences for and the Efficacy of Within- and Cross-Category Substitutes for Food

Young Eun Huh, Joachim Vosgerau & Carey Morewedge

Psychological Science, forthcoming

When people cannot get what they want, they often satisfy their desire by consuming a substitute. Substitutes can originate from within the taxonomic category of the desired stimulus (i.e., within-category substitutes) or from a different taxonomic category that serves the same basic goal (i.e., cross-category substitutes). Both a store-brand chocolate (within-category substitute) and a granola bar (cross-category substitute), for example, can serve as substitutes for gourmet chocolate. Here, we found that people believe that within-category substitutes, which are more similar to desired stimuli, will more effectively satisfy their cravings than will cross-category substitutes (Experiments 1, 2a, and 2b). However, because within-category substitutes are more similar than cross-category substitutes to desired stimuli, they are more likely to evoke an unanticipated negative contrast effect. As a result, unless substitutes are equivalent in quality to the desired stimulus, cross-category substitutes more effectively satisfy cravings for the desired stimulus (Experiments 3 and 4).


Persistent metabolic adaptation 6 years after “The Biggest Loser” competition

Erin Fothergill et al.

Obesity, forthcoming

Objective: To measure long-term changes in resting metabolic rate (RMR) and body composition in participants of “The Biggest Loser” competition.

Methods: Body composition was measured by dual energy X-ray absorptiometry, and RMR was determined by indirect calorimetry at baseline, at the end of the 30-week competition and 6 years later. Metabolic adaptation was defined as the residual RMR after adjusting for changes in body composition and age.

Results: Of the 16 “Biggest Loser” competitors originally investigated, 14 participated in this follow-up study. Weight loss at the end of the competition was (mean ± SD) 58.3 ± 24.9 kg (P < 0.0001), and RMR decreased by 610 ± 483 kcal/day (P = 0.0004). After 6 years, 41.0 ± 31.3 kg of the lost weight was regained (P = 0.0002), while RMR was 704 ± 427 kcal/day below baseline (P < 0.0001) and metabolic adaptation was −499 ± 207 kcal/day (P < 0.0001). Weight regain was not significantly correlated with metabolic adaptation at the competition's end (r = −0.1, P = 0.75), but those subjects maintaining greater weight loss at 6 years also experienced greater concurrent metabolic slowing (r = 0.59, P = 0.025).

Conclusions: Metabolic adaptation persists over time and is likely a proportional, but incomplete, response to contemporaneous efforts to reduce body weight.


An exploration of exercise-induced cognitive enhancement and transfer effects to dietary self-control

Cassandra Lowe, Dimitar Kolev & Peter Hall

Brain and Cognition, forthcoming

The primary objective of this study was to examine the effects of aerobic exercise on executive function, specifically inhibitory control, and the transfer to self-control in the dietary domain. It was hypothesized that exercise would enhance inhibitory control, and that this enhancement would facilitate self-control in a laboratory taste test paradigm. Using a crossover design, 51 participants completed counterbalanced sessions of both moderate exercise (experimental condition) and minimal effort walking (control condition) using a treadmill; the intersession interval was 7 days. Prior to each exercise bout participants completed a Stroop task. Following each bout participants completed a second Stoop task, as well as a bogus taste test involving three appetitive calorie dense snack foods and two control foods; the amount of each food type consumed during the taste test was covertly measured. Results revealed that moderate exercise significantly improved performance on the Stroop task, and also reduced food consumption during the taste test for appetitive calorie dense snack foods; there was no exercise effect on control food consumption. Exercise-induced gains in Stroop performance mediated the effects of moderate exercise on appetitive snack food consumption. Together these findings provide evidence that a bout of a moderate aerobic exercise can enhance inhibitory control, and support for cross-domain transfer effects to dietary self-control.


Satiety effects of psyllium in healthy volunteers

Jose Brum et al.

Appetite, forthcoming

Controlling hunger between meals is a challenge for many individuals. This manuscript comprises 2 sequential clinical trials investigating the effects of psyllium (Metamucil) on satiety, both using a randomized, double-blind, placebo-controlled cross-over design. The first study determined the effects of 3.4 g, 6.8 g, and 10.2 g of psyllium taken before breakfast and lunch for 3 days. The second study determined the effects of 6.8 g (taken before breakfast and lunch on Days 1 and 2 and before breakfast on Day 3) on the satiety of participants receiving an energy restricted meal in the morning (breakfast) for 3 days. Efficacy endpoints were mean inter-meal hunger, desire to eat, and Satiety Labeled Intensity Magnitude Visual Analog Scale scores. In Study 1, all 3 psyllium doses resulted in directional or statistically significant mean reduction in hunger and desire to eat, and increased fullness between meals compared to placebo, with both higher doses better than placebo or 3.4 g. The 6.8 g dose provided more consistent (p ≤ 0.013) satiety benefits versus placebo. In Study 2, satiety was assessed similarly to Study 1. A significant (p ≤ 0.004) decrease in the 3-day mean hunger and desire to eat, as well as an increase in fullness for psyllium relative to placebo was observed. Most adverse events were mild gastrointestinal symptoms and were similar for psyllium compared to placebo. These results indicate that psyllium supplementation contributes to greater fullness and less hunger between meals.


Believing in food addiction: Helpful or counterproductive for eating behavior?

Helen Ruddock et al.

Obesity, forthcoming

Methods: In two studies, female participants (study 1: N = 64; study 2: N = 90) completed food-related computerized tasks and were given bogus feedback on their performance which indicated that they had high, low, or average food addiction tendencies. Food intake was then assessed in an ad libitum taste test. Dietary concern and time taken to complete the taste test were recorded in study 2.

Results: In study 1, participants in the high-addiction condition consumed fewer calories than those in the low-addiction condition, F(1,60) = 7.61, P = 0.008, ηp2 = 0.11. Study 2 replicated and extended this finding, showing that the effect of the high-addiction condition on food intake was mediated by increased dietary concern, which reduced the amount of time participants willingly spent exposed to the foods during the taste test, b = −0.06 (0.03), 95% confidence interval = −0.13 to −0.01.

Conclusions: Believing oneself to be a food addict is associated with short-term dietary restriction. The longer-term effects on weight management now warrant attention.


Change in Body Mass Index Associated With Lowest Mortality in Denmark, 1976-2013

Shoaib Afzal et al.

Journal of the American Medical Association, 10 May 2016, Pages 1989-1996

Objective: To determine whether the BMI value that is associated with the lowest all-cause mortality has increased in the general population over a period of 3 decades.

Design, Setting, and Participants: Three cohorts from the same general population enrolled at different times: the Copenhagen City Heart Study in 1976-1978 (n = 13 704) and 1991-1994 (n = 9482) and the Copenhagen General Population Study in 2003-2013 (n = 97 362). All participants were followed up from inclusion in the studies to November 2014, emigration, or death, whichever came first.

Results: The number of deaths during follow-up was 10 624 in the 1976-1978 cohort (78% cumulative mortality; mortality rate [MR], 30/1000 person-years [95% CI, 20-46]), 5025 in the 1991-1994 cohort (53%; MR, 16/1000 person-years [95% CI, 9-30]), and 5580 in the 2003-2013 cohort (6%; MR, 4/1000 person-years [95% CI, 1-10]). Except for cancer mortality, the association of BMI with all-cause, cardiovascular, and other mortality was curvilinear (U-shaped). The BMI value that was associated with the lowest all-cause mortality was 23.7 (95% CI, 23.4-24.3) in the 1976-1978 cohort, 24.6 (95% CI, 24.0-26.3) in the 1991-1994 cohort, and 27.0 (95% CI, 26.5-27.6) in the 2003-2013 cohort. The corresponding BMI estimates for cardiovascular mortality were 23.2 (95% CI, 22.6-23.7), 24.0 (95% CI, 23.4-25.0), and 26.4 (95% CI, 24.1-27.4), respectively, and for other mortality, 24.1 (95% CI, 23.5-25.9), 26.8 (95% CI, 26.1-27.9), and 27.8 (95% CI, 27.1-29.6), respectively. The multivariable-adjusted hazard ratios for all-cause mortality for BMI of 30 or more vs BMI of 18.5 to 24.9 were 1.31 (95% CI, 1.23-1.39; MR, 46/1000 person-years [95% CI, 32-66] vs 28/1000 person-years [95% CI, 18-45]) in the 1976-1978 cohort, 1.13 (95% CI, 1.04-1.22; MR, 28/1000 person-years [95% CI, 17-47] vs 15/1000 person-years [95% CI, 7-31]) in the 1991-1994 cohort, and 0.99 (95% CI, 0.92-1.07; MR, 5/1000 person-years [95% CI, 2-12] vs 4/1000 person-years [95% CI, 1-11]) in the 2003-2013 cohort.

Conclusions and Relevance: Among 3 Danish cohorts, the BMI associated with the lowest all-cause mortality increased by 3.3 from cohorts enrolled from 1976-1978 through 2003-2013. Further investigation is needed to understand the reason for this change and its implications.

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