Caloric
Hunter-Gatherer Energetics and Human Obesity
Herman Pontzer et al.
PLoS ONE, July 2012
Abstract:
Western lifestyles differ markedly from those of our hunter-gatherer ancestors, and these differences in diet and activity level are often implicated in the global obesity pandemic. However, few physiological data for hunter-gatherer populations are available to test these models of obesity. In this study, we used the doubly-labeled water method to measure total daily energy expenditure (kCal/day) in Hadza hunter-gatherers to test whether foragers expend more energy each day than their Western counterparts. As expected, physical activity level, PAL, was greater among Hadza foragers than among Westerners. Nonetheless, average daily energy expenditure of traditional Hadza foragers was no different than that of Westerners after controlling for body size. The metabolic cost of walking (kcal kg-1 m-1) and resting (kcal kg-1 s-1) were also similar among Hadza and Western groups. The similarity in metabolic rates across a broad range of cultures challenges current models of obesity suggesting that Western lifestyles lead to decreased energy expenditure. We hypothesize that human daily energy expenditure may be an evolved physiological trait largely independent of cultural differences.
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Young Adult Obesity and Household Income: Effects of Unconditional Cash Transfers
Randall Akee et al.
American Economic Journal: Applied Economics, forthcoming
Abstract:
We investigate the effect of household cash transfers during childhood on young adult body mass indexes (BMI). The effects of extra income differ depending on the household's initial socio-economic status (SES). Children from the initially poorest households have a larger increase in BMI relative to children from initially wealthier households. Several alternative mechanisms are examined. Initial SES holds up as the most likely channel behind the heterogeneous effects of extra income on young adult BMI. Poverty generates long-term health vulnerabilities that cannot be fully mediated by public policy such as direct cash disbursements.
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Paschal Sheeran et al.
Health Psychology, forthcoming
Objective: Fantasy realization theory (Oettingen, 2012) proposes that fantasizing about a desired future or dwelling upon negative reality rarely changes behavior whereas mentally contrasting fantasy with reality can be an effective behavior change technique. This is because mental contrasting energizes people to overcome obstacles that stand in the way of their desired future. The present study tested whether mental contrasting promotes rates of physical activity among overweight, middle-aged, and low-SES men.
Method: A randomized controlled trial was conducted with members of an angling club in the north of England (N = 467). At baseline, participants completed a postal questionnaire that measured cognitions about physical activity. The intervention was embedded in the questionnaire for relevant participants. Behavior was followed up via telephone at 1 month and 7 months postbaseline. The key outcome measure was a validated, self-report measure of physical activity (Godin, Jobin & Bouillon, 1986) taken at all three time-points.
Results: Longitudinal, explanatory, and intention-to-treat analyses each indicated that mental contrasting was effective in enhancing rates of physical activity. Mental contrasting also aided the translation of beliefs about the value and worth of physical activity (instrumental attitudes) into action.
Conclusion: Mental contrasting appears to be an effective self-regulatory intervention for promoting physical activity and warrants further tests in health psychology.
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Childhood obesity and human capital accumulation
Tia Palermo & Jennifer Dowd
Social Science & Medicine, forthcoming
Abstract:
The prevalence of childhood obesity has tripled in the United States over the last 25 years, and in addition to increased risks of many chronic diseases, obesity may also be linked to lower skill attainment, poor social competency, and poorer labor outcomes. Any causal links between obesity and human capital accumulation could have important consequences for both health and economic well-being over the life course. We investigate the association of obesity and cognitive and non-cognitive outcomes among US children and adolescents aged 5 to 19 using the Child Development Supplement of the Panel Survey of Income Dynamics. We perform OLS and individual fixed effects regressions to address unobserved time invariant heterogeneity in the relationship between overweight/obesity and abilities. Results provide limited support for the hypothesis that obesity negatively affects non-cognitive but not cognitive outcomes and suggest that discrimination rather than a biological mechanism contributes to negative outcomes found in the literature on adults.
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Association of Weight Status With Mortality in Adults With Incident Diabetes
Mercedes Carnethon et al.
Journal of the American Medical Association, 8 August 2012, Pages 581-590
Context: Type 2 diabetes in normal-weight adults (body mass index [BMI] <25) is a representation of the metabolically obese normal-weight phenotype with unknown mortality consequences.
Objective: To test the association of weight status with mortality in adults with new-onset diabetes in order to minimize the influence of diabetes duration and voluntary weight loss on mortality.
Design, Setting, and Participants: Pooled analysis of 5 longitudinal cohort studies: Atherosclerosis Risk in Communities study, 1990-2006; Cardiovascular Health Study, 1992-2008; Coronary Artery Risk Development in Young Adults, 1987-2011; Framingham Offspring Study, 1979-2007; and Multi-Ethnic Study of Atherosclerosis, 2002-2011. A total of 2625 participants with incident diabetes contributed 27 125 person-years of follow-up. Included were men and women (age >40 years) who developed incident diabetes based on fasting glucose 126 mg/dL or greater or newly initiated diabetes medication and who had concurrent measurements of BMI. Participants were classified as normal weight if their BMI was 18.5 to 24.99 or overweight/obese if BMI was 25 or greater.
Main Outcome Measures: Total, cardiovascular, and noncardiovascular mortality.
Results: The proportion of adults who were normal weight at the time of incident diabetes ranged from 9% to 21% (overall 12%). During follow-up, 449 participants died: 178 from cardiovascular causes and 253 from noncardiovascular causes (18 were not classified). The rates of total, cardiovascular, and noncardiovascular mortality were higher in normal-weight participants (284.8, 99.8, and 198.1 per 10 000 person-years, respectively) than in overweight/obese participants (152.1, 67.8, and 87.9 per 10 000 person-years, respectively). After adjustment for demographic characteristics and blood pressure, lipid levels, waist circumference, and smoking status, hazard ratios comparing normal-weight participants with overweight/obese participants for total, cardiovascular, and noncardiovascular mortality were 2.08 (95% CI, 1.52-2.85), 1.52 (95% CI, 0.89-2.58), and 2.32 (95% CI, 1.55-3.48), respectively.
Conclusion: Adults who were normal weight at the time of incident diabetes had higher mortality than adults who are overweight or obese.
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V. Shier, R. An & R. Sturm
Public Health, forthcoming
Objectives: To examine the robustness of the relationship between neighbourhood food environment and youth body mass index (BMI) percentile using alternative measures of food environment and model specifications.
Study design: Observational study using individual-level longitudinal survey data of children in fifth and eighth grades merged with food outlet data based on student residential census tracts.
Methods: The relationship between food environment and BMI was examined with two individual outcomes (BMI percentile in eighth grade and change in BMI percentile from fifth to eighth grade) and three alternative measures of food environment (per-capita counts of a particular outlet type, food environment indices, and indicators for specific combinations of outlet types).
Results: No consistent evidence was found across measures (counts of a particular type of food outlet per population, food environment indices, and indicators for the presence of specific combinations of types of food stores) and outcomes to support the hypothesis that improved access to large supermarkets results in lower youth BMI; or that greater exposure to fast food restaurants, convenience stores and small food stores increases BMI.
Conclusions: To the extent that there is an association between food environment and youth BMI, the existence of more types of food outlets in an area, including supermarkets, is associated with higher BMI.
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Longitudinal Association Between Marital Disruption and Child BMI and Obesity
Jeremy Arkes
Obesity, August 2012, Pages 1696-1702
Abstract:
This research examines whether family disruptions (i.e., divorces and separation) contribute to children's weight problems. The sample consists of 7,299 observations for 2,333 children, aged 5-14, over the 1986-2006 period, from a US representative sample from the Child and Young Adult Survey accompanying the National Longitudinal Survey of Youth (NLSY). The study uses individual-fixed-effects models in a longitudinal framework to compare children's BMI and weight problems before and after a disruption. Furthermore, besides doing a before-after comparison for children, the study also estimates the effects at various periods relative to the disruption in order to examine whether children are affected before the disruption and whether any effects change as time passes from the disruption, as some effects may be temporary or slow to develop. Despite having a larger sample than the previous studies, the results provide no evidence that, on average, children's BMI and BMI percentile scores (measured with continuous outcomes) are affected before the disruption, after the disruption, and as time passes from the disruption, relative to a baseline period a few years before the disruption. However, children experiencing a family disruption do have an increased risk of obesity (having a BMI percentile score of 95 or higher) in the two years leading up to the disruption as well as after the disruption, and as time passes from the disruption.
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Is there evidence that friends influence body weight? A systematic review of empirical research
Solveig Cunningham et al.
Social Science & Medicine, October 2012, Pages 1175-1183
Abstract:
Researchers and policymakers from diverse fields are engaged in efforts to understand the biological and social causes of obesity in order to develop policies, interventions, and recommendations to stop or reverse increases in obesity. One potentially promising approach is to harness influence from social contacts. An important foundation for this approach involves critically analyzing available data regarding whether and how body weight can be affected by close social contacts, especially friends. This systematic review examines evidence from published studies addressing the influences of friends on body weight. The majority of the sixteen studies conclude that there is evidence of influence: six reported that friends influence body weight and ten reported evidence of influence in some circumstances or specifications. However, this literature sheds little light on mechanisms of influence. There is limited evidence that friends' communication about weight is associated with weight status and no compelling evidence that friends' behaviors affect one's weight. Many of the studies best designed to examine influence were the ones that did not explore mechanisms of influence. A priority for future research is to understand how, when, and how much friends affect the risk of obesity.
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Tiffany Cox et al.
Applied Research in Quality of Life, September 2012, Pages 309-322
Abstract:
Obesity not only increases risk for morbidity/mortality, but also impacts the quality of life of obese individuals. In the United States, black women have the highest prevalence of obesity of any other group with approximately 80% of black women over age 20 having a body mass index (BMI) ≥ 25 kg/m2. We aimed to examine the association between BMI and quality of life in this high risk population compared to this association in white women, using the Impact of Weight on Quality of Life (IWQOL)-Lite questionnaire. Data from 172 black women (mean BMI = 35.7; age = 40.5) and 171 white women (mean BMI = 35.5; age = 40.4) were collected between 2000 and 2010 analyzed in 2010. The mean IWQOL-Lite total score was 81.6 for black women compared to 66.9 for white women, a statistically significant difference. Hierarchical linear regression models revealed a significant BMI-by-race interaction indicating that the relationship between BMI and IWQOL-Lite score was moderated by race. Our findings suggest notable differences in weight-related quality of life in black and white women. At similar BMIs, black women consistently reported better quality of life than white women on all IWQOL-Lite subscales. The greatest difference in IWQOL-Lite scores between black and white women was seen in the self-esteem subscale. Additional research is needed to understand how to incorporate the weight perspectives of black women into weight management messages and interventions.
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Trends in the Prevalence of Abdominal Obesity and Overweight in English Adults (1993-2008)
Denise Howel
Obesity, August 2012, Pages 1750-1752
Abstract:
The rising prevalence of generalized obesity is well documented, but less is known about trends in abdominal obesity. Levels of abdominal obesity and overweight are reported for adults in the Health Survey for England (HSE) by survey year and age for 1993-2008. HSE is a nationally representative cross-sectional population survey using an interviewer-administered questionnaire and measurement of waist circumference (WC) by nurse, allowing calculation of abdominal overweight and obesity (≥94 cm and ≥102 cm in men, and ≥80 cm and ≥88 cm in women). A total of 40,001 men and 46,397 women aged 18-67 provided data on WC in this period. Between 1993 and 2008 abdominal overweight rose from 44.9% to 62.3% in men, and from 46.6% to 66.8% in women, while abdominal obesity rose from 19.2% to 35.7% in men, and from 23.8% to 43.9% women. However, the rates of increase over time in England appear to be slowing down: curves with a less than linear increase each year were a better fit to the data than a linear trend. There was some variation across the age range in the time trend in abdominal obesity and overweight, in that the absolute increases over time were slightly less for younger adults.
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Weight Status Among Adolescents in States That Govern Competitive Food Nutrition Content
Daniel Taber et al.
Pediatrics, forthcoming
Objectives: To determine if state laws regulating nutrition content of foods and beverages sold outside of federal school meal programs ("competitive foods") are associated with lower adolescent weight gain.
Methods: The Westlaw legal database identified state competitive food laws that were scored by using the Classification of Laws Associated with School Students criteria. States were classified as having strong, weak, or no competitive food laws in 2003 and 2006 based on law strength and comprehensiveness. Objective height and weight data were obtained from 6300 students in 40 states in fifth and eighth grade (2004 and 2007, respectively) within the Early Childhood Longitudinal Study-Kindergarten Class. General linear models estimated the association between baseline state laws (2003) and within-student changes in BMI, overweight status, and obesity status. Fixed-effect models estimated the association between law changes during follow-up (2003-2006) and within-student changes in BMI and weight status.
Results: Students exposed to strong laws at baseline gained, on average, 0.25 fewer BMI units (95% confidence interval: -0.54, 0.03) and were less likely to remain overweight or obese over time than students in states with no laws. Students also gained fewer BMI units if exposed to consistently strong laws throughout follow-up (β = -0.44, 95% confidence interval: -0.71, -0.18). Conversely, students exposed to weaker laws in 2006 than 2003 had similar BMI gain as those not exposed in either year.
Conclusions: Laws that regulate competitive food nutrition content may reduce adolescent BMI change if they are comprehensive, contain strong language, and are enacted across grade levels.
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Timothy Verstynen et al.
Psychosomatic Medicine, forthcoming
Objective: Obesity and decreased physical health are linked to deficits in several cognitive domains. The broad range of cognitive problems linked to obesity suggests a global mechanism that may interfere with multiple neural systems. We examined how variation in body mass index (BMI) is associated with the microstructural integrity of fiber connections in the human brain.
Methods: White matter structure was measured using diffusion tensor imaging in 28 participants (mean age = 30 years) with BMI scores ranging from normal weight to obese (19.5-45.7 kg/m2) based on standard BMI criteria.
Results: Using a whole-brain voxelwise analysis, we found that, across participants, the fractional anisotropy of white matter voxels parametrically decreased with increasing BMI (63% of white matter voxels). Midbrain and brainstem tracts were among the pathways most strongly associated with obesity (r = -0.18 to -0.33, df = 27, all p values < .05). We also observed a weaker overall diffusion signal in individuals with higher BMI than controls with normal weight (r = -0.14 to -0.71, df = 27, for 67% of fiber pathways tested, all p values < .05). After controlling for this decrease in general diffusivity, we found that decreases in fractional anisotropy stemmed from both a decrease in axial diffusivity (p < .05) and an increase in radial diffusivity (p < .05).
Conclusions: Our results show that increased BMI is globally associated with a reduction in white matter integrity throughout the brain, elucidating a potential mechanism by which changes in physical health may influence cognitive health.
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A.N. Payne, C. Chassard & C. Lacroix
Obesity Reviews, September 2012, Pages 799-809
Abstract:
The Western diet, comprised of highly refined carbohydrates and fat but reduced complex plant polysaccharides, has been attributed to the prevalence of obesity. A concomitant rise in the consumption of fructose and sugar substitutes such as sugar alcohols, artificial sweeteners, even rare sugars, has mirrored this trend, as both probable contributor and solution to the epidemic. Acknowledgement of the gut microbiota as a factor involved in obesity has sparked much controversy as to the cause and consequence of this relationship. Dietary intakes are a known modulator of gut microbial phylogeny and metabolic activity, frequently exploited to stimulate beneficial bacteria, promoting health benefits. Comparably little research exists on the impact of ‘unconscious' dietary modulation on the resident commensal community mediated by increased fructose and sugar substitute consumption. This review highlights mechanisms of potential host and gut microbial fructose and sugar substitute metabolism. Evidence is presented suggesting these sugar compounds, particularly fructose, condition the microbiota, resulting in acquisition of a westernized microbiome with altered metabolic capacity. Disturbances in host-microbe interactions resulting from fructose consumption are also explored.
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Elena Delgado-Rico et al.
Obesity, August 2012, Pages 1604-1610
Abstract:
Adolescent obesity is increasingly viewed as a brain-related dysfunction, whereby reward-driven urges for pleasurable foods "hijack" response selection systems, such that behavioral control progressively shifts from impulsivity to compulsivity. In this study, we aimed to examine the link between personality factors (sensitivity to reward (SR) and punishment (SP), BMI, and outcome measures of impulsivity vs. flexibility in - otherwise healthy - excessive weight adolescents. Sixty-three adolescents (aged 12-17) classified as obese (n = 26), overweight (n = 16), or normal weight (n = 21) participated in the study. We used psychometric assessments of the SR and SP motivational systems, impulsivity (using the UPPS-P scale), and neurocognitive measures with discriminant validity to dissociate inhibition vs. flexibility deficits (using the process-approach version of the Stroop test). We tested the relative contribution of age, SR/SP, and BMI on estimates of impulsivity and inhibition vs. switching performance using multistep hierarchical regression models. BMI significantly predicted elevations in emotion-driven impulsivity (positive and negative urgency) and inferior flexibility performance in adolescents with excess weight - exceeding the predictive capacity of SR and SP. SR was the main predictor of elevations in sensation seeking and lack of premeditation. These findings demonstrate that increases in BMI are specifically associated with elevations in emotion-driven impulsivity and cognitive inflexibility, supporting a dimensional path in which adolescents with excess weight increase their proneness to overindulge when under strong affective states, and their difficulties to switch or reverse habitual behavioral patterns.
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Endocannabinoids Measurement in Human Saliva as Potential Biomarker of Obesity
Isabelle Matias et al.
PLoS ONE, July 2012
Background: The discovery of the endocannabinoid system and of its role in the regulation of energy balance has significantly advanced our understanding of the physiopathological mechanisms leading to obesity and type 2 diabetes. New knowledge on the role of this system in humans has been acquired by measuring blood endocannabinoids. Here we explored endocannabinoids and related N-acylethanolamines in saliva and verified their changes in relation to body weight status and in response to a meal or to body weight loss.
Methodology/Principal Findings: Fasting plasma and salivary endocannabinoids and N-acylethanolamines were measured through liquid mass spectrometry in 12 normal weight and 12 obese, insulin-resistant subjects. Salivary endocannabinoids and N-acylethanolamines were evaluated in the same cohort before and after the consumption of a meal. Changes in salivary endocannabinoids and N-acylethanolamines after body weight loss were investigated in a second group of 12 obese subjects following a 12-weeks lifestyle intervention program. The levels of mRNAs coding for enzymes regulating the metabolism of endocannabinoids, N-acylethanolamines and of cannabinoid type 1 (CB1) receptor, alongside endocannabinoids and N-acylethanolamines content, were assessed in human salivary glands. The endocannabinoids 2-arachidonoylglycerol (2-AG), N-arachidonoylethanolamide (anandamide, AEA), and the N-acylethanolamines (oleoylethanolamide, OEA and palmitoylethanolamide, PEA) were quantifiable in saliva and their levels were significantly higher in obese than in normal weight subjects. Fasting salivary AEA and OEA directly correlated with BMI, waist circumference and fasting insulin. Salivary endocannabinoids and N-acylethanolamines did not change in response to a meal. CB1 receptors, ligands and enzymes were expressed in the salivary glands. Finally, a body weight loss of 5.3% obtained after a 12-weeks lifestyle program significantly decreased salivary AEA levels.
Conclusions/Significance: Endocannabinoids and N-acylethanolamines are quantifiable in saliva and their levels correlate with obesity but not with feeding status. Body weight loss significantly decreases salivary AEA, which might represent a useful biomarker in obesity.