Weight of history
Cohort of birth modifies the association between FTO genotype and BMI
James Niels Rosenquist et al.
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
A substantial body of research has explored the relative roles of genetic and environmental factors on phenotype expression in humans. Recent research has also sought to identify gene–environment (or g-by-e) interactions, with mixed success. One potential reason for these mixed results may relate to the fact that genetic effects might be modified by changes in the environment over time. For example, the noted rise of obesity in the United States in the latter part of the 20th century might reflect an interaction between genetic variation and changing environmental conditions that together affect the penetrance of genetic influences. To evaluate this hypothesis, we use longitudinal data from the Framingham Heart Study collected over 30 y from a geographically relatively localized sample to test whether the well-documented association between the rs993609 variant of the FTO (fat mass and obesity associated) gene and body mass index (BMI) varies across birth cohorts, time period, and the lifecycle. Such cohort and period effects integrate many potential environmental factors, and this gene-by-environment analysis examines interactions with both time-varying contemporaneous and historical environmental influences. Using constrained linear age–period–cohort models that include family controls, we find that there is a robust relationship between birth cohort and the genotype–phenotype correlation between the FTO risk allele and BMI, with an observed inflection point for those born after 1942. These results suggest genetic influences on complex traits like obesity can vary over time, presumably because of global environmental changes that modify allelic penetrance.
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Human embryos from overweight and obese women display phenotypic and metabolic abnormalities
Christine Leary, Henry Leese & Roger Sturmey
Human Reproduction, January 2015, Pages 122-132
Study question: Is the developmental timing and metabolic regulation disrupted in embryos from overweight or obese women?
Study design, size, duration: We have performed a retrospective, observational analysis of oocyte size and the subsequent developmental kinetics of 218 oocytes from 29 consecutive women attending for ICSI treatment and have related time to reach key developmental stages to maternal bodyweight. In addition, we have measured non-invasively the metabolic activity of 150 IVF/ICSI embryos from a further 29 consecutive women who donated their surplus embryos to research, and have related the data retrospectively to their body mass index (BMI).
Participants/materials, setting, methods: In a clinical IVF setting, we compared oocyte morphology and developmental kinetics of supernumerary embryos collected from overweight and obese women, with a BMI in excess of 25 kg/m2 to those from women of healthy weight. A Primovision Time-Lapse system was used to measure developmental kinetics and the non-invasive COnsumption/RElese of glucose, pyruvate, amino acids and lactate were measured on spent droplets of culture medium. Total triglyceride levels within individual embryos were also determined.
Main results and the role of chance: Human oocytes from women presenting for fertility treatment with a BMI exceeding 25 kg/m2 are smaller (R2 = −0.45; P = 0.001) and therefore less likely to complete development post-fertilization (P < 0.001). Those embryos that do develop reach the morula stage faster than embryos from women of a BMI < 25 kg/m2 (<0.001) and the resulting blastocysts contain fewer cells notably in the trophectoderm (P = 0.01). The resulting blastocysts also have reduced glucose consumption (R2 = −0.61; P = 0.001), modified amino acid metabolism and increased levels of endogenous triglyceride (t = 4.11, P < 0.001). Our data further indicate that these differences are independent of male BMI.
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Chris Fradkin et al.
Health Psychology, January 2015, Pages 1-9
Objective: This study examined the association between socioeconomic status (SES) and obesity risk during early adolescence, ages 10–13 years, and whether this association is present in different racial/ethnic and gender groups during 2 time points in early adolescence.
Method: Data were from the Healthy Passages study, which enrolled 4,824 African American, Hispanic, and White 5th graders (ages 10–11) in a population-based, longitudinal study conducted in 3 U.S. metropolitan areas, and assessed them again 2 years later. Weight status was classified from measured body mass index using standard criteria into nonobese and obese (27% in 5th grade). SES was indexed based on highest education attainment in the household.
Results: Youth in the highest SES had a significantly lower prevalence of obesity than those of lower SES at both 5th and 7th grades when disregarding race/ethnicity. Within-racial/ethnic group analyses mostly confirmed this pattern for Hispanic and White youth, but not for African American youth. When also considering gender, the SES differential in obesity risk was more pronounced among White girls and 5th-grade Hispanic boys.
Conclusion: Growing up in a high SES home, marked by having a member with at least a college degree, is associated with lower risk for obesity among Hispanic and White youth. For African American youth, there appears to be no association between SES and obesity. Thus the health advantage generally attributed to higher SES does not appear consistently across racial/ethnic groups for obesity in youth. Further research should identify influences on weight status beyond SES, especially among African American youth.
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Fast Food Consumption and Academic Growth in Late Childhood
Kelly Purtell & Elizabeth Gershoff
Clinical Pediatrics, forthcoming
Objective: The objective of this study is to examine the associations between fast food consumption and the academic growth of 8544 fifth-grade children in reading, math, and science.
Method: This study uses direct assessments of academic achievement and child-reported fast food consumption from a nationally representative sample of kindergartners followed through eighth grade.
Results: More than two thirds of the sample reported some fast food consumption; 20% reported consuming at least 4 fast food meals in the prior week. Fast food consumption during fifth grade predicted lower levels of academic achievement in all 3 subjects in eighth grade, even when fifth grade academic scores and numerous potential confounding variables, including socioeconomic indicators, physical activity, and TV watching, were controlled for in the models.
Conclusion: These results provide initial evidence that high levels of fast food consumption are predictive of slower growth in academic skills in a nationally representative sample of children.
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Eric Robinson, Paul Aveyard & Susan Jebb
Obesity, forthcoming
Objectives: Identifying eating behaviors which contribute to excess weight gain will inform obesity prevention strategies. A tendency to clear one's plate when eating may be a risk factor for obesity in an environment where food is plentiful. Whether plate clearing is associated with increased body weight in a cohort of US participants was examined.
Methods: Nine hundred and ninety-three US adults (60% male, 80% American European, mean age = 31 years) completed self-report measures of habitual plate clearing together with behavioral and demographic characteristics known to be associated with obesity.
Results: Plate clearing tendencies were positively associated with BMI and remained so after accounting for a large number of other demographic and behavioral predictors of BMI in analyses (β = 0.18, 95% CIs = 0.07, 0.29, P < 0.001); an increased tendency to plate clear was associated with a significantly higher body weight.
Conclusions: The tendency to clear one's plate when eating is associated with increased body weight and may constitute a risk factor for weight gain.
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Effects of subtle and explicit health messages on food choice
Heather Scherschel Wagner, Maryhope Howland & Traci Mann
Health Psychology, January 2015, Pages 79-82
Objective: Explicitly — as opposed to subtly — labeling a food healthy may inadvertently license people to indulge, imply that the food tastes bad, or lead to reactance. We investigated the effects of explicit and subtle health messages on individuals’ food selection in two field studies.
Method: We manipulated the signs on healthy foods such that they explicitly stated that the food was healthy, subtly suggested it with an image, or did not mention health. As participants — attendees at academic conferences — approached registration tables, research assistants recorded the number and type of snacks individuals chose.
Results: Participants were more likely to choose the healthy food when it was labeled with the subtle health message than when it was labeled with the explicit health message, which itself was not more effective than the control message.
Conclusion: Subtle messages may be more useful than explicit health messages in encouraging individuals to make a healthy snack choice.
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Unemployment and Health Behaviors Over the Business Cycle: A Longitudinal View
Gregory Colman & Dhaval Dave
NBER Working Paper, December 2014
Abstract:
We examine the first-order internal effects of unemployment on a range of health behaviors during the most recent recession using longitudinal data from the Panel Study of Income Dynamics (PSID) and the National Longitudinal Survey of Youth 1979 (NLSY79). Consistent with prior studies based on cross-sectional data, we find that becoming unemployed is associated with a small increase in leisure-time exercise and in body weight, a moderate decrease in smoking, and a substantial decline in total physical activity. We also find that unemployment is associated with a decline in purchases of fast food. Together, these results imply that both energy consumption and expenditure decline in the U.S. during recessions, the net result being a slight increase in body weight. There is generally considerable heterogeneity in these effects across specific health behaviors, across the intensive and extensive margins, across the outcome distribution, and across gender.
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The effects of old and new media on children’s weight
Agne Suziedelyte
Applied Economics, Winter 2015, Pages 1008-1018
Abstract:
Childhood obesity rates have recently been rising in many countries. It has been suggested in the literature that changes in children’s media exposure may contribute to explaining this trend. I investigate whether or not this hypothesis is supported by data. I contribute to the literature by focusing not only on television but also on new media – computers and video games. The Child Development Supplement to the Panel Study of Income Dynamics is used for the analysis. To address the endogeneity of children’s media exposure, I use dynamic and panel data models. This is another improvement upon the existing literature. Additionally, an extensive list of control variables is included in the regressions. I find that video game playing or computer use has no effect on children’s body weight. On the other hand, television viewing may increase children’s body weight slightly.
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Spatial-Temporal Modeling of Neighborhood Sociodemographic Characteristics and Food Stores
Archana Lamichhane et al.
American Journal of Epidemiology, forthcoming
Abstract:
The literature on food stores, neighborhood poverty, and race/ethnicity is mixed and lacks methods of accounting for complex spatial and temporal clustering of food resources. We used quarterly data on supermarket and convenience store locations from Nielsen TDLinx (Nielsen Holdings N.V., New York, New York) spanning 7 years (2006–2012) and census tract–based neighborhood sociodemographic data from the American Community Survey (2006–2010) to assess associations between neighborhood sociodemographic characteristics and food store distributions in the Metropolitan Statistical Areas (MSAs) of 4 US cities (Birmingham, Alabama; Chicago, Illinois; Minneapolis, Minnesota; and San Francisco, California). We fitted a space-time Poisson regression model that accounted for the complex spatial-temporal correlation structure of store locations by introducing space-time random effects in an intrinsic conditionally autoregressive model within a Bayesian framework. After accounting for census tract–level area, population, their interaction, and spatial and temporal variability, census tract poverty was significantly and positively associated with increasing expected numbers of supermarkets among tracts in all 4 MSAs. A similar positive association was observed for convenience stores in Birmingham, Minneapolis, and San Francisco; in Chicago, a positive association was observed only for predominantly white and predominantly black tracts. Our findings suggest a positive association between greater numbers of food stores and higher neighborhood poverty, with implications for policy approaches related to food store access by neighborhood poverty.
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Perceived stress and freshman weight change: The moderating role of baseline body mass index
Jessica Boyce & Roeline Kuijer
Physiology & Behavior, February 2015, Pages 491–496
Abstract:
The transition from high-school to university is a critical period of weight change. Popular media suggest that freshman students gain 15 lb (6.80 kg) of body weight during their first year at university (i.e., the freshman 15). In contrast, a recent meta-analysis calculated freshman weight gain to be 1.75 kg, with statistics suggesting that only a proportion of freshman students are prone to gain weight. Researchers are beginning to investigate how certain variables and interactions between such variables predict freshman weight status. The current study focused on body mass index (BMI) and psychological stress. In isolation, previous research has tested how these two variables predict freshman student's weight status. However, because BMI and stress interact to predict weight gain and weight loss in adult samples, the current study tested the interaction between student's baseline BMI and baseline stress levels to predict weight change in a New Zealand sample of freshman students (N = 65). Participants completed two separate online surveys in March and October 2012 (i.e., New Zealand's academic year). Although only three students gained over 6.80 kg (i.e., the freshman 15), participants did gain a statistically significant 1.10 kg of body weight during the year. Consistent with previous research, students with a higher baseline BMI gained a higher amount of body weight. However, this main effect was qualified by an interaction between stress and BMI. Students who entered university with high levels of stress gained weight if they also had high BMIs; if they had lower BMIs then they lost weight. In order to reduce unhealthy levels of freshman weight change, vulnerable students need to be taught stress-reduction techniques and coping strategies early in the academic year.
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The weight of stigma: Cortisol reactivity to manipulated weight stigma
Mary Himmelstein, Angela Incollingo Belsky & Janet Tomiyama
Obesity, forthcoming
Objective: Rates of weight-based stigmatization have steadily increased over the past decade. The psychological and physiological consequences of weight stigma remain understudied.
Methods: This study examined the effects of experimentally manipulated weight stigma on the stress-responsive hypothalamic–pituitary–adrenal axis (HPA) in 110 female undergraduate participants (BMI: M = 19.30, SD = 1.55). Objective BMI and self-perceived body weight were examined as moderators of the relationship between stigma and HPA reactivity.
Results: Results indicated participants' perceptions of their own body weight (but not objective BMI) moderated the effect of weight stigma on cortisol reactivity: F(1,102) = 13.48, P < 0.001, η2p = 0.12 (interaction 95% CI range [−2.06 to −1.44, −1.31 to −0.99]). Specifically, participants who perceived themselves as heavy exhibited sustained cortisol elevation post-manipulation compared with individuals who did not experience the weight-related stigma. Cortisol change did not vary by condition for participants who perceived themselves as average weight.
Conclusions: In the first study to examine physiological consequences of active interpersonal exposure to weight stigma, experiencing weight stigma was stressful for participants who perceived themselves as heavy, regardless of their BMI. These results are important because stress and cortisol are linked to deleterious health outcomes, stimulate eating, and contribute to abdominal adiposity.
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Slave to habit? Obesity is associated with decreased behavioural sensitivity to reward devaluation
Annette Horstmann et al.
Appetite, forthcoming
Abstract:
The motivational value of food is lower during satiety compared to fasting. Dynamic changes in motivational value promote food seeking or meal cessation. In obesity this mechanism might be compromised since obese subjects ingest energy beyond homeostatic needs. Thus, lower adaptation of eating behaviour with respect to changes in motivational value might cause food overconsumption in obesity. To test this hypothesis, we implemented a selective satiation procedure to investigate the relationship between obesity and the size of the behavioural devaluation effect in humans. Lean to obese men (mean age 25.9, range 19-30 years; mean BMI 29.1, range 19.2-45.1 kg/m2) were trained on a free operant paradigm and learned to associate cues with the possibility to win different food rewards by pressing a button. After the initial training phase, one of the rewards was devalued by consumption. Response rates for and wanting of the different rewards were measured pre and post devaluation. Behavioural sensitivity to reward devaluation, measured as the magnitude of difference between pre and post responses, was regressed against BMI. Results indicate that (1) higher BMI compared to lower BMI in men led to an attenuated behavioural adjustment to reward devaluation, and (2) the decrease in motivational value was associated with the decrease in response rate between pre and post. Change in explicitly reported motivational value, however, was not affected by BMI. Thus, we conclude that high BMI in men is associated with lower behavioural adaptation with respect to changes in motivational value of food, possibly resulting in automatic overeating patterns that are hard to control in daily life.
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Kerri Boutelle et al.
International Journal of Obesity, forthcoming
Objective: There is evidence of altered neural taste response in female adolescents who are obese, and in adolescents who are at risk for obesity. To further understand risk factors for the development of overeating and obesity, we investigated response to tastes of sucrose and water in 23 obese and healthy weight children.
Methods and design: Thirteen healthy weight (HW) and 10 obese (OB) 8-12 year old children underwent functional magnetic resonance imaging while tasting sucrose and water. Additionally, children completed an eating in the absence of hunger paradigm and a sucrose liking task.
Results: A region of interest analysis revealed an elevated BOLD response to taste (sucrose and water) within the bilateral insula and amygdala in OB children relative to HW children. Whole brain analyses revealed a group by condition interaction within the paracingulate, medial frontal, middle frontal gyri, and right amygdala: post hoc analyses suggested an increased response to sucrose for OB relative to HW children, whereas HW children responded more strongly to water relative to sucrose. In addition, OB children, relative to HW, tended to recruit the right putamen as well as medial and lateral frontal and temporal regions bilaterally.
Conclusion: This study showed increased reactivity in the amygdala and insula in the OB compared to HW children, but no functional differentiation in the striatum, despite differences in the striatum previously seen in older samples. These findings support the concept of the association between increased neural processing of food reward in the development of obesity, and raise the possibility that emotional and interoceptive sensitivity could be an early vulnerability in obesity.
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Weight training, aerobic physical activities, and long-term waist circumference change in men
Rania Mekary et al.
Obesity, forthcoming
Objective: Findings on weight training and waist circumference (WC) change are controversial. This study examined prospectively whether weight training, moderate to vigorous aerobic activity (MVAA), and replacement of one activity for another were associated with favorable changes in WC and body weight (BW).
Methods: Physical activity, WC, and BW were reported in 1996 and 2008 in a cohort of 10,500 healthy U.S. men in the Health Professionals Follow-up Study. Multiple linear regression models (partition/substitution) to assess these associations were used.
Results: After adjusting for potential confounders, a significant inverse dose-response relationship between weight training and WC change (P-trend <0.001) was observed. Less age-associated WC increase was seen with a 20-min/day activity increase; this benefit was significantly stronger for weight training (−0.67 cm, 95% CI −0.93, −0.41) than for MVAA (−0.33 cm, 95% CI −0.40, −0.27), other activities (−0.16 cm, 95% CI −0.28, −0.03), or TV watching (0.08 cm, 95% CI 0.05, 0.12). Substituting 20 min/day of weight training for any other discretionary activity had the strongest inverse association with WC change. MVAA had the strongest inverse association with BW change (−0.23 kg, 95% CI −0.29, −0.17).
Conclusions: Among various activities, weight training had the strongest association with less WC increase. Studies on frequency/volume of weight training and WC change are warranted.
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Black and White Body Mass Index Values in Developing Nineteenth Century Nebraska
Scott Alan Carson
Journal of Biosocial Science, January 2015, Pages 105-119
Abstract:
Little is known about late 19th and early 20th century BMIs on the US Central Plains. Using data from the Nebraska state prison, this study demonstrates that the BMIs of dark complexioned blacks were greater than for fairer complexioned mulattos and whites. Although modern BMIs have increased, late 19th and early 20th century BMIs in Nebraska were in normal ranges; neither underweight nor obese individuals were common. Farmer BMIs were consistently greater than those of non-farmers, and farm labourer BMIs were greater than those of common labourers. The BMIs of individuals born in Plains states were greater than for other nativities, indicating that rural lifestyles were associated with better net current biological living conditions.