Six Pack
The Effect of Exercise on Earnings: Evidence from the NLSY
Vasilios Kosteas
Journal of Labor Research, June 2012, Pages 225-250
Abstract: This paper investigates whether engaging in regular exercise leads to higher earnings in the labor market. While there has been a recent surge of interest by economists on the issue of obesity, relatively little attention has been given to the economic effects of regular physical activity apart from its impact on body composition. I find that engaging in regular exercise yields a 6 to 10% wage increase. The results also show that while even moderate exercise yields a positive earnings effect, frequent exercise generates an even larger impact. These findings are fairly robust to a variety of estimation techniques, including propensity score matching.
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The Heterogeneity of the Cigarette Price Effect on Body Mass Index
George Wehby & Charles Courtemanche
NBER Working Paper, May 2012
Abstract: Previous studies estimate the average effect of cigarette price on body mass index (BMI), with recent research showing that their different methodologies all point to a negative effect after several years. This literature, however, ignores the possibility that the effect could vary throughout the BMI distribution or across socioeconomic and demographic groups due to differences in underlying preferences for health or risks for obesity. We evaluate heterogeneity in the long-run impact of cigarette price on BMI by performing quantile regressions and stratifying the sample by race, education, age, and sex. Cigarette price has a highly heterogeneous negative effect that is more than three times as strong at high BMI levels - where weight loss is most beneficial for health - than at low levels. The effects are also strongest for blacks, college graduates, middle-aged adults, and women. We also assess the implications for disparities, conduct robustness checks, and evaluate potential mechanisms.
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Family mealtimes: A contextual approach to understanding childhood obesity
Barbara Fiese, Amber Hammons & Diana Grigsby-Toussaint
Economics & Human Biology, forthcoming
Abstract: There has been a growing interest in the role that shared family mealtimes may play in promoting the health and well-being of children. Families that regularly eat their main meal together four or more times a week are more likely to have children who do better in school, are of average weight, less likely to use drugs and alcohol at an early age, and consume more fruits and vegetables. The mere fact that families eat together does not address the process by which shared family mealtimes may protect children from unhealthy weight gain. Just as there is no simple explanation for the rising rates of obesity, the link between shared family mealtimes and childhood obesity is a complex one including socioeconomic and cultural context. In this paper, we provide an overview of how shared family mealtimes are embedded in a socio-cultural context that may either support or derail healthy eating patterns for children and youth. Evidence from an observational study of 200 family mealtimes demonstrates the complex interplay between socio-economic factors, family mealtime behaviors, and child obesity status. Families who had a child of healthy weight spent more time engaged with each other during the meal, expressed more positive communication, and considered mealtimes more important and meaningful than families who had a child who was overweight or obese. Using a cumulative risk model, it was found that the combination of family level and neighborhood risk factors predicted child overweight status. Recommendations are made for future research directions and policies directed toward families living in diverse economic circumstances.
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Susanna Huh et al.
Archives of Disease in Childhood, forthcoming
Objective: To examine whether delivery by caesarean section is a risk factor for childhood obesity.
Design: Prospective prebirth cohort study (Project Viva).
Setting: Eight outpatient multi-specialty practices based in the Boston, Massachusetts area.
Participants: We recruited women during early pregnancy between 1999 and 2002, and followed their children after birth. We included 1255 children with body composition measured at 3 years of age.
Main outcome measures: BMI score, obesity (BMI for age and sex ≥95th percentile), and sum of triceps plus subscapular skinfold thicknesses at 3 years of age.
Results: 284 children (22.6%) were delivered by caesarean section. At age 3, 15.7% of children delivered by caesarean section were obese compared with 7.5% of children born vaginally. In multivariable logistic and linear regression models adjusting for maternal prepregnancy BMI, birth weight, and other covariates, birth by caesarean section was associated with a higher odds of obesity at age 3 (OR 2.10, 95% CI 1.36 to 3.23), higher mean BMI z-score (0.20 units, 95% CI 0.07 to 0.33), and higher sum of triceps plus subscapular skinfold thicknesses (0.94 mm, 95% CI 0.36 to 1.51).
Conclusions: Infants delivered by caesarean section may be at increased risk of childhood obesity. Further studies are needed to confirm our findings and to explore mechanisms underlying this association.
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Breastfeeding and risk of overweight and obesity at nine-years of age
Cathal McCrory & Richard Layte
Social Science & Medicine, July 2012, Pages 323-330
Abstract: Whether breastfeeding is protective against the development of childhood overweight and obesity remains the subject of considerable debate. Although a number of meta-analyses and syntheses of the literature have concluded that the greater preponderance of evidence indicates that breastfeeding reduces the risk of obesity, these findings are by no means conclusive. The present study used data from the Growing Up in Ireland study to examine the relationship between retrospectively recalled breastfeeding data and contemporaneously measured weight status for 7798 children at nine-years of age controlling for a wide range of variables including; socio-demographic factors, the child's own lifestyle-related behaviours, and parental BMI. The results of the multivariable analysis indicated that being breastfed for between 13 and 25 weeks was associated with a 38 percent (p < 0.05) reduction in the risk of obesity at nine-years of age, while being breastfed for 26 weeks or more was associated with a 51 percent (p < 0.01) reduction in the risk of obesity at nine-years of age. Moreover, results pointed towards a dose-response patterning in the data for those breastfed in excess of 4 weeks. Possible mechanisms conveying this health benefit include slower patterns of growth among breastfed children, which it is believed, are largely attributable to differences in the composition of human breast milk compared with synthesised formula. The suggestion that the choice of infant feeding method has important implications for health and development is tantalising as it identifies a modifiable health behaviour that is amenable to intervention in primary health care settings and has the potential to improve the health of the population.
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Obesity, Family Instability, and Socioemotional Health in Adolescence
Robert Crosnoe
Economics & Human Biology, forthcoming
Abstract: The last two decades have witnessed dramatic increases in obesity and family instability. To the extent that the social stigma of obesity is a risk factor and family instability represents the potential compromise of important protective factors, their convergence may disrupt socioemotional health, especially during periods of heightened social uncertainty. Drawing on data from the National Longitudinal Study of Adolescent Health, this study found that obese youth at the start of high school had higher levels of internalizing symptoms and lower levels of perceived social integration in school only when they had also experienced multiple family transitions since birth. This pattern, however, did not hold for boys, and it did not extend to overweight (as opposed to obese) adolescents of either gender.
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The value of medical and pharmaceutical interventions for reducing obesity
Pierre-Carl Michaud et al.
Journal of Health Economics, forthcoming
Abstract: This paper attempts to quantify the social, private, and public-finance values of reducing obesity through pharmaceutical and medical interventions. We find that the total social value of bariatric surgery is large for treated patients, with incremental social cost-effectiveness ratios typically under $10,000 per life-year saved. On the other hand, pharmaceutical interventions against obesity yield much less social value with incremental social cost-effectiveness ratios around $50,000. Our approach accounts for: competing risks to life expectancy; health care costs; and a variety of non-medical economic consequences (pensions, disability insurance, taxes, and earnings), which account for 20% of the total social cost of these treatments. On balance, bariatric surgery generates substantial private value for those treated, in the form of health and other economic consequences. The net public fiscal effects are modest, primarily because the size of the population eligible for treatment is small while the net social effect is large once improvements in life expectancy are taken into account.
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Income Inequality and Obesity Prevalence among OECD Countries
Dejun Su et al.
Journal of Biosocial Science, July 2012, Pages 417-432
Abstract: Using recent pooled data from the World Health Organization Global Infobase and the World Factbook compiled by the Central Intelligence Agency of the United States, this study assesses the relation between income inequality and obesity prevalence among 31 OECD countries through a series of bivariate and multivariate linear regressions. The United States and Mexico well lead OECD countries in both obesity prevalence and income inequality. A sensitivity analysis suggests that the inclusion or exclusion of these two extreme cases can fundamentally change the findings. When the two countries are included, the results reveal a positive correlation between income inequality and obesity prevalence. This correlation is more salient among females than among males. Income inequality alone is associated with 16% and 35% of the variations in male and female obesity rates, respectively, across OECD countries in 2010. Higher levels of income inequality in the 2005-2010 period were associated with a more rapid increase in obesity prevalence from 2002 to 2010. These associations, however, virtually disappear when the US and Mexico have been excluded from the analysis. Findings from this study underscore the importance of assessing the impact of extreme cases on the relation between income inequality and health outcomes. The potential pathways from income inequality to the alarmingly high rates of obesity in the cases of the US and Mexico warrant further research.
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Parental Employment, Family Routines and Childhood Obesity
Patricia Anderson
Economics & Human Biology, forthcoming
Abstract: Using the Early Childhood Longitudinal Survey-Kindergarten Class of 1998-99 (ECLS-K) data from kindergarten through eighth grade, this paper investigate the relationships among maternal employment, family routines and obesity. More hours worked by the mother tend to be negatively related to positive routines like eating meals as a family or at regular times, or having family rules about hours of television watched. Many of these same routines are significantly related to the probability of being obese, implying that family routines may be a mechanism by which maternal employment intensity affects children's obesity. However, inclusion of family routines in the obesity regression does not appreciably change the estimated effect of maternal employment hours. Thus, the commonly-estimated deleterious effect of maternal employment on children's obesity cannot be explained by family routines, leaving the exact mechanisms an open question for further exploration.
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Anorexia Nervosa and Obesity are Associated with Opposite Brain Reward Response
Guido Frank et al.
Neuropsychopharmacology, forthcoming
Abstract: Anorexia nervosa (AN) is a severe psychiatric disorder associated with food avoidance and malnutrition. In this study, we wanted to test whether we would find brain reward alterations in AN, compared with individuals with normal or increased body weight. We studied 21 underweight, restricting-type AN (age M 22.5, SD 5.8 years), 19 obese (age M 27.1, SD 6.7 years), and 23 healthy control women (age M 24.8, SD 5.6 years), using blood oxygen level-dependent functional magnetic resonance brain imaging together with a reward-conditioning task. This paradigm involves learning the association between conditioned visual stimuli and unconditioned taste stimuli, as well as the unexpected violation of those learned associations. The task has been associated with activation of brain dopamine reward circuits, and it allows the comparison of actual brain response with expected brain activation based on established neuronal models. A group-by-task condition analysis (family-wise-error-corrected P<0.05) indicated that the orbitofrontal cortex differentiated all three groups. The dopamine model reward-learning signal distinguished groups in the anteroventral striatum, insula, and prefrontal cortex (P<0.001, 25 voxel cluster threshold), with brain responses that were greater in the AN group, but lesser in the obese group, compared with controls. These results suggest that brain reward circuits are more responsive to food stimuli in AN, but less responsive in obese women. The mechanism for this association is uncertain, but these brain reward response patterns could be biomarkers for the respective weight state.
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Till Roenneberg et al.
Current Biology, 22 May 2012, Pages 939-943
Abstract: Obesity has reached crisis proportions in industrialized societies. Many factors converge to yield increased body mass index (BMI). Among these is sleep duration. The circadian clock controls sleep timing through the process of entrainment. Chronotype describes individual differences in sleep timing, and it is determined by genetic background, age, sex, and environment (e.g., light exposure). Social jetlag quantifies the discrepancy that often arises between circadian and social clocks, which results in chronic sleep loss. The circadian clock also regulates energy homeostasis, and its disruption - as with social jetlag - may contribute to weight-related pathologies. Here, we report the results from a large-scale epidemiological study, showing that, beyond sleep duration, social jetlag is associated with increased BMI. Our results demonstrate that living "against the clock" may be a factor contributing to the epidemic of obesity. This is of key importance in pending discussions on the implementation of Daylight Saving Time and on work or school times, which all contribute to the amount of social jetlag accrued by an individual. Our data suggest that improving the correspondence between biological and social clocks will contribute to the management of obesity.
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Sleep Duration and BMI in a Sample of Young Adults
Katie Meyer et al.
Obesity, June 2012, Pages 1279-1287
Abstract: We examined the association between sleep duration and BMI in young adults, and, specifically, in possible gender differences. The population-based sample included 955 young men and 1051 young women (mean age = 25.3 years, s.d. = 1.7) who participated in Project EAT-III (Eating and Activity in Teens and Young Adults)-III. In 2008-2009, study participants completed a survey, on which they reported their weight, height, and typical bed and awakening times. Gender-specific regression models estimated cross-sectional associations between sleep duration and weight status, adjusting for age, race, SES, family structure, depressive symptoms, physical activity, and sedentary and dietary behaviors. In multivariable-adjusted linear regression models, an hour increase in sleep was associated with a -0.38 (-0.70, -0.048) BMI in men. Men who slept <7 h had a 1.4 unit higher mean BMI (27.9; 95% confidence interval (CI): 26.9, 28.9) than men who slept 7-9 h/day (26.5; 95% CI: 26.1, 27.0). Prevalence estimates of overweight (BMI ≥25) and obesity (BMI ≥30) were also inversely associated with sleep duration among men. Sleep duration was not associated with BMI, overweight, or obesity in women. Among women, but not men, there was a statistically significant positive association between trouble falling or staying asleep and mean BMI. Sleep may be an important modifiable risk factor for obesity, particularly in young adult men.
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Euna Han & Lisa Powell
Contemporary Economic Policy, forthcoming
Abstract: With a parallel increase in the consumption of food away from home, particularly fast food, and the obesity prevalence in the United States, evidence on the potential effectiveness of fiscal pricing policies to curb obesity is needed. We estimate changes in the dispersion of the entire conditional distribution of body mass index (BMI) associated with changes in fast food prices for adults using the National Longitudinal Survey of Youth 1979 in cross-sectional and longitudinal quantile regression models. We find that the ordinary least squares estimate for men underestimates the negative relationship of fast food prices with BMI at the 50th and upper quantiles in cross-sectional models although the statistical significance disappears in the longitudinal individual fixed effects quantile regression. Among subpopulations, we find that a 10% increase in the price of fast food is associated with 0.9% and 0.7% lower BMI for low-income women and women with any children, respectively, at the 90th quantile in a longitudinal individual fixed effects model. Our results imply that fiscal pricing policies such as fast food taxes might have a greater impact on the weight outcomes of low-income women or women with children in the upper tail of the conditional BMI distribution.
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Within-Family Variation in Obesity
Joseph Price & Jeffrey Swigert
Economics & Human Biology, forthcoming
Abstract: We use data from the Children of the National Longitudinal Survey of Youth 1979 to document the degree to which childhood obesity varies among siblings. We find considerable differences in body weight between siblings with over half of the siblings differing by more than 20 age-specific percentiles in terms of the body mass index. Even among identical twins, there is an average BMI difference of 12 percentiles. This variation is important for the use of econometric approaches that involve sibling comparisons.
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The Impact of Prepregnancy Obesity on Children's Cognitive Test Scores
Rika Tanda et al.
Maternal and Child Health Journal, forthcoming
Abstract: To examine the association between maternal prepregnancy obesity and cognitive test scores of children at early primary school age. A descriptive observational design was used. Study subjects consist of 3,412 US children aged 60-83 months from the National Longitudinal Survey of Youth 1979 Mother and Child Survey. Cognitive test scores using the Peabody Individual Achievement Test reading recognition and mathematics tests were used as the outcomes of interest. Association with maternal prepregnancy obesity was examined using the ordinary least square regression controlling for intrauterine, family background, maternal and child factors. Children of obese women had 3 points (0.23 SD units) lower peabody individual achievement test (PIAT) reading recognition score (p = 0.007), and 2 points (0.16 SD units) lower PIAT mathematics scores (p < 0.0001), holding all other factors constant. As expected, cognitive test score was associated with stimulating home environment (reading: β = 0.15, p < 0.0001, and math: β = 0.15, p < 0.0001), household income (reading: β = 0.03, p = 0.02 and math: β = 0.04, p = 0.004), maternal education (reading: β = 0.42, p = 0.0005, and math: β = 0.32, p = 0.008), and maternal cognitive skills (reading: β = 0.11, p < 0.0001, and math: β = 0.09, p < 0.0001). There was a significant association between maternal prepregnancy obesity and child cognitive test scores that could not be explained by other intrauterine, family background, maternal, and child factors. Children who live in disadvantaged postnatal environments may be most affected by the effects of maternal prepregnancy obesity. Replications of the current study using different cohorts are warranted to confirm the association between maternal prepregnancy obesity and child cognitive test scores.
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Inducing Negative Affect Increases the Reward Value of Appetizing Foods in Dieters
Dylan Wagner et al.
Journal of Cognitive Neuroscience, July 2012, Pages 1625-1633
Abstract: Experiencing negative affect frequently precedes lapses in self-control for dieters, smokers, and drug addicts. Laboratory research has similarly shown that inducing negative emotional distress increases the consumption of food or drugs. One hypothesis for this finding is that emotional distress sensitizes the brain's reward system to appetitive stimuli. Using functional neuroimaging, we demonstrate that inducing negative affect in chronic dieters increases activity in brain regions representing the reward value of appetitive stimuli when viewing appetizing food cues. Thirty female chronic dieters were randomly assigned to receive either a negative (n = 15) or neutral mood induction (n = 15) immediately followed by exposure to images of appetizing foods and natural scenes during fMRI. Compared with chronic dieters in a neutral mood, those receiving a negative mood induction showed increased activity in the OFC to appetizing food images. In addition, activity to food images in the OFC and ventral striatum was correlated with individual differences in the degree to which the negative mood induction decreased participants' self-esteem. These findings suggest that distress sensitizes the brain's reward system to appetitive cues, thereby offering a mechanism for the oft-observed relationship between negative affect and disinhibited eating.
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Per Gustafsson, Mats Persson & Anne Hammarström
European Journal of Public Health, June 2012, Pages 322-327
Background: Obesity and body mass in adulthood relate both to current and to childhood socio-economic status, particularly in women, but the underlying life course processes are not known. This study aims at examining whether the life course socio-economic status - body mass association in women and men is explained by the cumulative risk or adolescent sensitive period models whether associations are similar at different life course stages; and whether health behaviours explain the associations.
Methods: A total of 476 women and 517 men participated in this 27-year prospective cohort study (participation rate 93%). Body mass index was assessed at the age of 16 and 43 years and self-reported at the age of 21 and 30 years. Information on socio-economic status by own or parental (age 16 years) occupation, smoking, snuff, alcohol, physical activity and diet was collected at each age.
Results: In women, cumulative socio-economic status and socio-economic status in adolescence were related to body mass index at the age of 16, 21, 30 and 43 years and to the 27-year change in body mass, independently of health behaviours and for adolescent socio-economic status also of later socio-economic attainment. Associations were generally stronger for body mass at older age. In men, associations were mostly non-significant, although health behaviours contributed strongly to body mass.
Conclusions: In women, both the sensitive period (in adolescence) and cumulative risk models explain the socio-economic-body mass link. Efforts to reduce the social inequality in body mass in women should be directed at the early life course, but focusing on unhealthy behaviours might not be a sufficient approach.
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Changing BMI Categories and Healthcare Expenditures Among Elderly Medicare Beneficiaries
Tricia Lee Wilkins, George Rust & Usha Sambamoorthi
Obesity, June 2012, Pages 1240-1248
Abstract: To examine the association between changes in BMI categories and health-care expenditures among elderly Medicare beneficiaries using longitudinal data of the Medicare Current Beneficiary Survey (MCBS) 2000-2005. Changes in BMI were (i) Stayed Normal: individuals with a normal BMI at baseline and follow-up; (ii) Stayed Overweight individuals with overweight BMI at baseline and follow-up; (iii) Stayed Obese individuals with obese BMI at baseline and follow-up; (iv) Normal-Overweight: individuals with normal BMI at baseline and overweight BMI at follow-up; (v) Overweight-Obese: individuals with overweight BMI at baseline and obese BMI at follow-up; (vi) Overweight-Normal: individuals with overweight BMI at baseline and normal BMI at follow-up; (vii) Obese-Overweight: individuals with obese BMI at baseline and overweight BMI at follow-up. Ordinary Least Squares (OLS) models on logged Year 3 expenditures were used to analyze changes in expenditures between BMI categories. Overall, 35% Stayed Normal, 34% Stayed Overweight, 18% Stayed Obese, 4% gained weight from Normal-Overweight BMI, 3% gained weight from Overweight-Obese BMI, 5% lost weight from Overweight-Normal BMI, and 3% lost weight from Obese-Overweight BMI. Adjusted models revealed those who Stayed Obese had increased total and multiple expenditure types that were significantly higher than Stayed Normal including total (11%), outpatient (25%), prescription (9%), and medical provider (4%). Compared to Stayed Normal, total expenditures were both 26% higher for Obese-Overweight and Overweight-Obese. The current findings highlight the importance of maintaining a normal BMI in the elderly.
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Rahul Agrawal & Fernando Gomez-Pinilla
Journal of Physiology, 1 May 2012, Pages 2485-2499
Abstract: We pursued studies to determine the effects of the metabolic syndrome (MetS) on brain, and the possibility of modulating these effects by dietary interventions. In addition, we have assessed potential mechanisms by which brain metabolic disorders can impact synaptic plasticity and cognition. We report that high-dietary fructose consumption leads to an increase in insulin resistance index, and insulin and triglyceride levels, which characterize MetS. Rats fed on an n-3 deficient diet showed memory deficits in a Barnes maze, which were further exacerbated by fructose intake. In turn, an n-3 deficient diet and fructose interventions disrupted insulin receptor signalling in hippocampus as evidenced by a decrease in phosphorylation of the insulin receptor and its downstream effector Akt. We found that high fructose consumption with an n-3 deficient diet disrupts membrane homeostasis as evidenced by an increase in the ratio of n-6/n-3 fatty acids and levels of 4-hydroxynonenal, a marker of lipid peroxidation. Disturbances in brain energy metabolism due to n-3 deficiency and fructose treatments were evidenced by a significant decrease in AMPK phosphorylation and its upstream modulator LKB1 as well as a decrease in Sir2 levels. The decrease in phosphorylation of CREB, synapsin I and synaptophysin levels by n-3 deficiency and fructose shows the impact of metabolic dysfunction on synaptic plasticity. All parameters of metabolic dysfunction related to the fructose treatment were ameliorated by the presence of dietary n-3 fatty acid. Results showed that dietary n-3 fatty acid deficiency elevates the vulnerability to metabolic dysfunction and impaired cognitive functions by modulating insulin receptor signalling and synaptic plasticity.
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Altered processing of sweet taste in the brain of diet soda drinkers
Erin Green & Claire Murphy
Physiology & Behavior, forthcoming
Abstract: Artificially sweetened beverage consumption has been linked to obesity, and it has been hypothesized that considerable exposure to nonnutritive sweeteners may be associated with impaired energy regulation. The reward system plays an integral role in modulating energy intake, but little is known about whether habitual use of artificial sweetener (i.e., diet soda consumption) may be related to altered reward processing of sweet taste in the brain. To investigate this, we examined fMRI response after a 12-hour fast to sucrose (a nutritive sweetener) and saccharin (a nonnutritive sweetener) during hedonic evaluation in young adult diet soda drinkers and non-diet soda drinkers. Diet soda drinkers demonstrated greater activation to sweet taste in the dopaminergic midbrain (including ventral tegmental area) and right amygdala. Saccharin elicited a greater response in the right orbitofrontal cortex (Brodmann Area 47) relative to sucrose in non-diet soda drinkers. There was no difference in fMRI response to the nutritive or nonnutritive sweetener for diet soda drinkers. Within the diet soda drinkers, fMRI activation of the bilateral caudate head in response to saccharin was negatively associated with the amount of diet sodas consumed per week; individuals who consumed a greater number of diet sodas had reduced caudate head activation. These findings suggest that there are alterations in reward processing of sweet taste in individuals who regularly consume diet soda, and this is associated with the degree of consumption. These findings may provide some insight into the link between diet soda consumption and obesity.
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Khosrow Houschyar et al.
BMC Medicine, May 2012
Background: Metabolic syndrome (METS) is an increasingly prevalent but poorly understood clinical entity characterized by insulin resistance, glucose intolerance, dyslipidemia, hypertension and obesity. Increased oxidative stress catalyzed by accumulation of iron in excess of physiologic requirements has been implicated in the pathogenesis of METS but cause-and-effect relationships remain uncertain. The hypothesis that phlebotomy-induced reduction of body iron stores would alter clinical manifestations of METS was tested by a randomized trial.
Methods: In a randomized-controlled single-blinded clinical trial 64 patients with METS were randomly assigned to iron reduction by phlebotomy (n=33) or to a waiting-list control group (n=31). Iron reduction patients had 300ml of blood removed at entry and between 250-500ml removed after 4 weeks depending on entry ferritin levels. Primary outcomes were change of systolic blood pressure and of insulin sensitivity as measured by HOMA-Index after 6 weeks. Secondary outcomes included HbA1c, plasma-glucose, blood lipids and heart rate.
Results: Systolic blood pressure decreased from 148.5+/-12.3 mmHg to 130.5+/-11.8 mm Hg in the phlebotomy group and from 144.7+/-14.4 mmHg to 143.8+/-11.9 mmHg in the control group (difference -16.6 mmHg;95%-CI:-20.7;-12.5;p<0.001). No significant effect on the HOMA-Index was observed. Among secondary outcomes, blood glucose, HbA1c, LDL/HDL ratio and heart rate were significantly decreased by phlebotomy. Changes in blood pressure and HOMA-Index were correlated with reduction of ferritin.
Conclusions: In patients with METS, phlebotomy with consecutive reduction of body iron stores lowered blood pressure and resulted in improvements of markers of cardiovascular risk and glycemic control. Blood donation may have beneficial effects for donating subjects with METS.
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Ghrelin Levels Increase After Pictures Showing Food
Petra Schüssler et al.
Obesity, June 2012, Pages 1212-1217
Abstract: The neuropeptide ghrelin is a major signal for food intake in various species including humans. After exogenous ghrelin administration, food intake and body weight increase in rodents. In normal human subjects, ghrelin administration increases self-rated appetite and calorie intake and prompts the imagination of favorite meals. It is unclear so far whether ghrelin levels are affected by external cues such as sight of food. We investigated the influence of pictures showing food compared to neutral pictures on ghrelin levels in young normal male subjects (n = 8). The study consisted of two consecutive sessions with a one-week interval. During each session, blood for later analysis of plasma concentrations of ghrelin was collected between 08:15 and 13:00 every 15 min (between 10:30 and 11:30 every 10 min). Breakfast and lunch was provided at 08:30 and 12:00, respectively. Fifty pictures were presented from 10:30 to 10:45 showing neutral images during the first session and food contents during the second session. As expected, ghrelin levels increased before each meal independent of the picture contents. In addition, ghrelin levels during the 30-min interval following the presentation of pictures with food increased significantly compared to the 30-min interval before this presentation (area under the curve (AUC): 188 % vs. 158 %, P < 0.05). The difference in the increases between the two picture conditions was also significant (P < 0.05). Our findings suggest that sight of food elevates ghrelin levels in healthy volunteers.
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Adverse Metabolic Response to Regular Exercise: Is It a Rare or Common Occurrence?
Claude Bouchard et al.
PLoS ONE, May 2012
Background: Individuals differ in the response to regular exercise. Whether there are people who experience adverse changes in cardiovascular and diabetes risk factors has never been addressed.
Methodology/Principal Findings: An adverse response is defined as an exercise-induced change that worsens a risk factor beyond measurement error and expected day-to-day variation. Sixty subjects were measured three times over a period of three weeks, and variation in resting systolic blood pressure (SBP) and in fasting plasma HDL-cholesterol (HDL-C), triglycerides (TG), and insulin (FI) was quantified. The technical error (TE) defined as the within-subject standard deviation derived from these measurements was computed. An adverse response for a given risk factor was defined as a change that was at least two TEs away from no change but in an adverse direction. Thus an adverse response was recorded if an increase reached 10 mm Hg or more for SBP, 0.42 mmol/L or more for TG, or 24 pmol/L or more for FI or if a decrease reached 0.12 mmol/L or more for HDL-C. Completers from six exercise studies were used in the present analysis: Whites (N = 473) and Blacks (N = 250) from the HERITAGE Family Study; Whites and Blacks from DREW (N = 326), from INFLAME (N = 70), and from STRRIDE (N = 303); and Whites from a University of Maryland cohort (N = 160) and from a University of Jyvaskyla study (N = 105), for a total of 1,687 men and women. Using the above definitions, 126 subjects (8.4%) had an adverse change in FI. Numbers of adverse responders reached 12.2% for SBP, 10.4% for TG, and 13.3% for HDL-C. About 7% of participants experienced adverse responses in two or more risk factors.
Conclusions/Significance: Adverse responses to regular exercise in cardiovascular and diabetes risk factors occur. Identifying the predictors of such unwarranted responses and how to prevent them will provide the foundation for personalized exercise prescription.
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Marketing of Vice Goods: A Strategic Analysis of the Package Size Decision
Sanjay Jain
Marketing Science, January/February 2012, Pages 36-51
Abstract: Consumers are often unable to resist the temptation of overconsuming certain products such as cookies, crackers, soft drinks, alcohol, etc. To control their consumption, some consumers buy small packages or abstain from purchasing the product altogether. Other consumers, however, still purchase large packages and overconsume. From a strategic perspective, firms have the option of introducing small packages or only offering large packages. We use the literature on hyperbolic discounting to model consumers' self-control problems and examine conditions under which firms will offer small packages to help consumers combat their self-control problem, and how this offering in turn affects prices, profits, consumer, and social welfare. Our results show that introducing small packages can increase firms' profits only when a small fraction of consumers have overconsumption problems or when small packages can bring in new customers. Additionally, we find that competition can sometimes reduce the incentives for firms to introduce small packages. This is particularly true when a large fraction of consumers is attracted to small packages. We also find that firms' profits can sometimes decrease if they produce healthier alternatives of their goods. Our analysis of consumer welfare reveals that small packages enhance consumer and social welfare, even though they sometimes increase the consumption of vice goods.