BMI Measures Research Articles

Differences in traditional and emerging cardiovascular risk factors of subjects discordantly classified by metabolic syndrome definitions of the International Diabetes Federation and the National Cholesterol Education Program

Background and aim Several working definitions of metabolic syndrome have been proposed for clinical use. However, individuals can be discordantly classified as having or not having metabolic syndrome depending on the choice of one or another definition. This study compared the cardiovascular risk profile of subjects concordantly and discordantly diagnosed by the criteria of the National Cholesterol Education Program (NCEP) and the criteria of the International Diabetes Federation (IDF). Methods and results Nine hundred and twenty-nine non-diabetic adult subjects belonging to a cross-sectional population-based study in Gran Canaria island (Spain) were assessed. Participants completed a questionnaire and underwent physical examination, fasting blood analyses, and a standardized oral glucose tolerance test. Two hundred and four subjects (22%) had metabolic syndrome according to both definitions, 31 (3.3%) only by the IDF criteria, and 5 (0.5%) only by the NCEP criteria. Participants fulfilling both proposals showed more adverse age and sex-adjusted measures of BMI, waist, HDL cholesterol, triglycerides, post-load glucose, HOMA-IR and plasminogen inhibitor activator-1 (PAI-1) than individuals exclusively satisfying the IDF criteria. Moreover, in contrast to subjects meeting both criteria, those that fulfilled only the IDF criteria had levels of BMI, waist, total and HDL cholesterol, post-load glucose, glycated HbA1c, C-reactive protein, PAI-1 and fibrinogen not significantly different from those observed in subjects without metabolic syndrome. Conclusion The IDF definition identifies a surplus of individuals whose cardiovascular risk profile, particularly regarding to some non-traditional cardiovascular risk factors, is less adverse than that observed in subjects also diagnosed by the NCEP definition.

Raised CRP Levels in Obese Patients: Symptoms of Depression Have an Independent Positive Association

Depression and obesity, the two common ailments of modern society, are associated with increased risk of coronary artery disease and raised C-reactive protein (CRP) levels. Are the effects of depression and obesity related or do they influence CRP levels independently? In 493 consecutive patients presenting for obesity surgery, we explored the relationship between symptoms of depression and raised CRP levels after controlling for confounding factors. Depression was measured using the Beck Depression Inventory (BDI). Confounding variables were age, gender, BMI, waist and hip measures, smoking and alcohol habits, medications, biochemical measures of the metabolic syndrome, and indirect measures of insulin resistance. General linear regression sought variables independently associated with CRP levels. These patients had a BMI range from 31 to 91 kg/m2, participants age ranged from 14 to 71 years, and 76% were women. The median CRP concentration was 7.7mg/l (interquartile range: 3.9-14), 40% had an abnormally raised concentration (> 10mg/l). The mean BDI score was 17.0 +/- 9.0, indicating symptoms of moderate depression. We found five independent factors associated with raised CRP levels. In order of strength of association, these were: higher BMI (beta = 0.36, P < 0.001), female gender (beta = -0.19, P < 0.001), estrogen therapy (beta = 0.18, P < 0.001), higher BDI score (beta = 0.11, P = 0.01), and insulin resistance index (beta = 0.11, P = 0.01), and with a combined R2 = 0.24, (P < 0.001). In obese patients, symptoms of depression were associated with raised CRP levels after controlling for confounding variables. Obese women on estrogen therapy are at risk of high CRP levels.

Estimating peer effects on health in social networks: A response to Cohen-Cole and Fletcher; and Trogdon, Nonnemaker, and Pais

In July of 2007, we published a paper in the New England Journal of Medicine that used dynamic data over 32 years from the Framingham Heart Study Social Network (FHS-Net) to study the conditions under which obesity might spread from person to person (Christakis and Fowler 2007, hereafter, CF). We found that obese persons formed clusters in the network at all time points and that these clusters extended to three degrees of separation (e.g., to a person’s friend’s friend’s friend). Moreover, statistical analyses suggested that the clusters were not solely attributable to the selective formation of social ties among obese persons. A person’s chances of becoming obese increased if he or she had a friend who became obese in a given time period. Our analyses were restricted to adults, so a natural question to ask is whether or not the results would generalize to a population of adolescents. The existence of social norms regarding weight in both adults and adolescents should not be surprising,(Chang and Christakis 2003) but, of course, causal inference in dyads, let alone in broader social networks, is difficult (Manski 1993). These questions are addressed by two papers in this issue, “Is Obesity Contagious? Social Networks versus Environmental Factors in the Obesity Epidemic,” by Ethan Cohen-Cole and Jason Fletcher (hereafter CCF) and “Peer Effects in Adolescent Overweight,” by Justin Trogdon, James Nonnemaker, and Joanne Pais (hereafter TNP), and by a third working paper “Identifying Endogenous Peer Effects in the Spread of Obesity” by Timothy J. Halliday and Sally Kwak (hereafter HK). All three of these papers analyze the same dataset and population, the National Longitudinal Study of Adolescent Health (Add Health), albeit with different methods and assumptions. Unlike the FHS-Net, which followed adults over a 32-year period (average age 38 in 1971), AddHealth followed adolescents over a 7-year period (average age 16 in 1995). All three sets of authors take the possibility of peer effects seriously, advancing the study of this important area. HK summarize their results by noting that they are able to replicate the pattern of results in our study, although their results are sensitive to specification of the dependent variable. If weight is characterized by a dichotomous variable indicating overweight (BMI>25), then an association between friends is significant, but the association in the continuous measure of BMI is not. Similarly, TNP use a variety of econometric strategies to conclude that there are peer effects for obesity in the Add Health sample, especially among females and among adolescents with high BMI. For example, they use an instrumental variables approach and a variety of definitions of endogenous peer groups to control for contextual effects. Here, we particularly address the CCF paper since it is the only one of the three papers that claims to reject the hypothesis that weight status can spread from person to person. To their credit, CCF exploit longitudinal data in a way that TNP and HK do not, but there are important problems in both their analysis and their interpretation of the results.

The Predictive Utility of a Behaviorally-Based Screening Tool for Detecting Family Obesigenic Environments

PURPOSE: The purpose of the study is to evaluate the predictive utility of a simple screening tool for assessing family nutrition and physical activity (FNPA) environments. It was hypothesized that family environments (assessed with the FNPA screening tool) would predict 1 year change in BMI after controlling for baseline BMI and parental BMI. METHODS: Nurses from 37 of the 39 elementary schools in a large urban district participated and collectively provided height and weight data from 2058 first graders in the district (~92%). Nurses distributed FNPA surveys to parents and a total of 1030 surveys were returned (~50% return rate) along with consent forms allowing follow-up BMI tests the following year. A total of 704 participants (68% Caucasian) had complete data on the FNPA and both BMI measures. These data were used in subsequent longitudinal analyses. Logistic regression was used to evaluate the ability of the overall FNPA score to predict which children were classified at or above the 85th percentile ('at risk for overweight' or 'overweight'). Mixed model regression analyses were used to examine whether the FNPA score could explain variability in 1 year BMI change after controlling for baseline BMI and inherited family risk. RESULTS: A FNPA risk score was computed using beta-weights from cross sectional regression analyses performed on the baseline data. Children with a total score in the lowest tertile (high risk family environment) had an odds ratio (OR) of 1.7 compared to children with a total score in the highest tertile (low risk family environment). Mixed model regression analyses revealed considerable variability between schools in BMI (between school variance = 1.26, ICC=.097) but this was almost completely removed when baseline BMI was entered into the model (residual between school variance = .029). There were no significant effects from race or gender but parent risk and the FNPA total score explained unique variance when added to the model. CONCLUSIONS: These results support the predictive utility of the FNPA for characterizing family 'obesigenic' environment. While the overall effect was small in absolute terms it is noteworthy considering the strength of family history factors. Additional research is needed to evaluate the utility for school-based screening.

Steps/day, BMI in 54-59 Year Old Women by Self-reported Occupational Sitting and Leisure Physical Activity

PURPOSE: To assess the relationships between self-reported occupational sitting and leisure time physical activity (PA) with pedometer-determined PA (steps/day) and objectively measured BMI in 54-59 year old women. METHODS: 158 women (age=56.4±1.4 years; BMI=26.9±5.4 kg/m2), were measured directly for height and weight (later used to compute BMI), wore a Yamax SW-700 (Tokyo, Japan) pedometer for 5 consecutive weekdays, and reported occupational sitting time (mostly/all of the time vs. some/little/no time) and weekly frequency and duration of participation in leisure time walking, moderate and vigorous PA (subsequently categorized as sufficiently active or insufficiently active based on achieving 600 MET-min). Four total PA groups were formed: 1) sufficiently active and some/little/no occupational sitting (n=52), 2) sufficiently active and mostly/all occupational sitting (n=29), 3) insufficiently active and some/little/no occupational sitting (n=43), and 4) insufficiently active and mostly/all occupational sitting (n=34). Pearson correlations were used to assess relationships between steps/day and BMI. ANOVA was used to examine differences in mean steps/day and BMI across the four total PA groups. RESULTS: The correlation between steps/day and BMI was r=−.419 (p<.001). Mean±SD for steps/day for each of the defined four PA groups were: 1) 10,285±3,065; 2) 9,606±3,421; 3) 9,180±3,029; and, 4) 7,470±3,299, respectively (F=5.537, p<.001). Mean±SD for BMI were, respectively: 1) 25.5±3.9; 2) 26.9±4.1; 3) 26.5±4.7; and, 4) 29.7±7.9 (F=4.57, p<.005). Post-hoc LSD tests revealed that mean steps/ day were significantly lower, and BMI was significantly higher, in the fourth group (insufficiently active and mostly/all occupational sitting) compared with all other groups; no other differences were significant. CONCLUSIONS: In 54-59 year old women, those reporting a combination of sedentary behaviors at work and during leisure time were most compromised in terms of objectively measured PA and BMI. Self-reporting participation in either sufficient amounts of leisure time PA or limited time sitting at work was associated with similar objective measures of PA and BMI as found in the most overall active women, suggesting either approach might be appropriate in terms of intervention.

Vigorous Physical Activity Determines Magnitude of Cardiovascular Risk Factor Changes Following Physical Activity Interventions

Physical activity (PA) is a significant determinant of good health yet it continues to decline in most countries. Interventions promoting PA are therefore important public health initiatives. PURPOSE: To measure the impact of 40-days intensive PA on CV and metabolic risk factors, and to follow subjects for 6 months to document both PA patterns and risk factor changes. METHODS: Two 40-day programs were designed to increase PA among insufficiently active adults randomly assigned to a: (1) pedometer-based (n=251), or (2) group-based intervention arm (n=187). An active control group was also followed (n=135). The pedometer subjects were advised about the 10,000-step goal and provided diaries and pedometers. Group subjects used heart rate monitors to record all daily sessions. Half the sessions were led while the others were performed individually. Sessions gradually progressed to vigorous levels of activity. Health risk factors including fitness parameters were measured pre- and post-intervention, and at 3 and 6 months follow-up. RESULTS: Adherence rates at post intervention, 3 and 6 months were 84, 69 and 61% for pedometer and 86, 76 and 71% for group subjects. Significant improvements occurred in cholesterol, BMI, VO2max, waist girth, and total and vigorous PA measures during both 40-day intervention arms. Repeated measures ANOVA showed significant group × intervention interactions for all these variables (group > pedometer, p<0.01). Regression analysis showed changes for cholesterol and VO2max, between each test over the study period, were significantly related to the corresponding changes in vigorous PA but not moderate PA (p<0.0001). BMI changes were related to both. Repeated measures ANOVA (using intention to treat analysis) showed significant improvements remained at 6 months for VO2max, BMI, and both total and vigorous minutes of PA for both intervention arms. Improvements remained for cholesterol at 3 months. CONCLUSION: Significant changes in risk factor profiles were found in both interventions over the 40-day program and most improvements remained at 6 months. Vigorous PA was significantly associated with the magnitude of risk factor changes. Supported by the South Australian Department of Health and Australian Research Council.

Obesity and Type 2 Diabetes Risk in Midadult Life: The Role of Childhood Adversity

Child abuse has been associated with poorer physical health in adulthood, but less is known about childhood adversity more broadly, including neglect and family problems, or the pathways from adversity to adult disease. We have examined how different stressful emotional or neglectful childhood adversities are related to adiposity and glucose control in midadulthood, taking into account childhood factors, and whether the relationships are mediated by adult health behaviors and socioeconomic position. This was a prospective longitudinal study of 9310 members of the 1958 British birth cohort who participated in a biomedical interview at 45 years of age. Primary outcomes consisted of continuous measures of BMI, waist circumference, and glycosylated hemoglobin at 45 years and categorical indicators: total obesity (BMI > or = 30), central obesity (waist circumference: > or = 102 cm for men and > or = 88 cm for women), and glycosylated hemoglobin level of > or = 6. The risk of obesity increased by 20% to 50% for several adversities (physical abuse, verbal abuse, witnessed abuse, humiliation, neglect, strict upbringing, physical punishment, conflict or tension, low parental aspirations or interest in education, hardly takes outings with parents, and father hardly reads to child). Adversities with the strongest associations with adiposity (eg, physical abuse) tended to be associated with glycosylated hemoglobin levels of > or = 6, but in most cases associations were explained by adjustment for adulthood mediators such as adiposity. Effects of other adversities reflecting less severe emotional neglect and family environment were largely explained by childhood socioeconomic factors. Some childhood adversities increase the risk of obesity in adulthood and thereby increase the risk for type 2 diabetes. Research is needed to understand the interrelatedness of adversities, the social context of their occurrence, and trajectories from adversity to adult disease.

Dietary energy density and diet variety as predictors of outcome in anorexia nervosa

BackgroundAnorexia nervosa (AN) is a serious psychiatric illness associated with significant morbidity and mortality. Successful treatment results in weight restoration, but recidivism is common, and the rate of relapse is estimated to be as high as 50%. Maintenance of a healthy diet is central to the recovery process, but the relation between diet and relapse has not been investigated in AN patients. ObjectiveThe objective of the study was to determine whether diet energy density and diet variety in recently weight-restored women with AN predict outcome. DesignAfter gaining weight to a body mass index (BMI; in kg/m2) of ≥20, 47 hospitalized women completed 4-d food records, from which a mean diet energy density score (DEDS) and a mean diet variety score (DVS) were calculated. Outcome was determined at study end by using modified Morgan-Russell criteria, and it was dichotomized as “treatment success” or “treatment failure.” Data were analyzed by using Student's t test. A logistic regression model was constructed to evaluate the effects of DEDS, DVS, and caloric intake on outcome. ResultsGroups did not differ significantly in mean measures of age, admission and weight-restored BMI, or caloric intake. However, DEDS and DVS were significantly higher in the success group than in the failure group. The success and failure groups were followed for a mean of 240 and 170 d, respectively. In the logistic regression model, DEDS (P = 0.016) and DVS (P = 0.048) but not caloric intake (P = 0.585) significantly predicted outcome. ConclusionIn recently weight-restored women with AN, lower DEDS and DVS but not caloric intake were associated with poor outcome.

Serum retinol binding protein is more strongly associated with retinol than measures of insulin sensitivity and BMI in fasted obese adults

Elevated serum retinol binding protein (RBP), the major carrier of vitamin A, has been linked to obesity and type 2 diabetes, suggesting therapeutic potential in lowering blood concentrations. Obese men and women (BMI &gt; 30) (n = 76) were fasted for ≥ 8 hr prior to blood collection. Blood chemistries were obtained. Retinol and retinyl esters were quantified by HPLC and RBP by ELISA. The relations between serum RBP, retinol and retinyl esters as well as measures of insulin sensitivity and BMI were determined using the Pearson correlation for simple associations and multiple linear regression for multivariate models. Retinol and RBP were .0001) with a molar ratio (retinol:RBP) of 0.73 ± 0.14. RBP was not associated with BMI, glucose, insulin or the homeostatic model assessment (HOMA) (P &gt; 0.05), but was inversely associated with the glucose/insulin ratio (r = −0.31, P &lt; 0.02). In multivariate models, only retinol and the glucose/insulin ratio were significant explanatory variables for RBP. Total serum retinyl ester concentration was positively associated with retinol (r = 0.30, P &lt; 0.01) and the association was strengthened after the removal of three potentially hypervitaminotic subjects (retinyl ester ≥ 10% total retinol) from the sample (r = 0.48, P &lt; 0.0001). When evaluating the therapeutic potential of lowering serum RBP, consequences on vitamin A metabolism should be considered.

Childhood overweight prevention programs: Evidence for success

Background: A previous review showed 67% of childhood obesity interventions to be effective. Aim: This study is an update of that review, focusing on interventions to prevent childhood overweight. Methods: Included are diet or physical activity related interventions, targeting children 6 to 19 years of age, evaluated using anthropometric outcomes, and published in a peer review journal. Excluded are treatment programs, interventions targeting high risk children, and pilot studies. Intervention effectiveness is defined by statistically significant differences for BMI or skin‐fold outcomes compared to the control. Results: Forty interventions met the inclusion and exclusion criteria, 17 were new studies. From this total, 31 (78%) were effective, mostly short term. Nineteen studies reported both BMI and skin‐fold outcomes, 10 were effective by skinfolds (53%) and 7 were effective by BMI (37%). Seven studies were effective only for girls, two only for boys. Conclusions: The differences in BMI versus skin‐folds outcomes could be due to increased physical activity or measurement error. However, the difference in BMI versus skin‐folds explains why Cochrane reviews, focusing on BMI measures, draw less optimistic conclusions. Interventions may need to target boys and girls differently. Overall, most interventions are effective in the short term.

A retrospective comparison of two very low energy diets on weight loss and health status in obese women completing a 26-week program

To retrospectively compare the effects of two very low energy diets (VLED) on weight, girths, and health status by auditing clinic database. Obese women (n = 150) who consumed either 420 kcal/day (n = 75) or 800 kcal/day (n = 75) were retrospectively matched for age, height and entry weight. The 26-week program comprised 12 weeks of 420 or 800 kcal/day energy intake then 12 weeks of reintroduction of normal food, with behavioural management. Pre-post measures of weight, BMI, girths, blood pressure (BP) and blood glucose, cholesterol and triglycerides were made. Within groups, all variables significantly improved at 26 weeks, except fasting glucose (420 group only). In the 420 and 800 groups, mean weight loss was 18.7 and 19.0 kg, BMI reduced by 7.7 and 7.0 kg/m(2), waist girth by 15.6 and 16.2 cm and hip girth by 16.5 and 14.1 cm (all p < 0.001). With weight loss expressed as % of entry weight, 58.7% of the 420 and 42.6% of the 800 groups lost >20% weight (p = 0.05). The only post-between group differences were in decreases in systolic BP (14 mmHg in 420 vs. 7 mmHg in 800; p < 0.05) and fasting glucose (0.1 mmol/L in 420 vs. 0.4 mmo1/L in 800; p < 0.05). Both levels of VLED with behavioural management produced similar improvements in weight and health status in obese women after 26 weeks. A VLED of 800 kcal/day (instead of 420) might be recommended for calorie control programs, to minimise health risks, while producing similar improvements in weight and health.

Central Rather Than Overall Obesity Is Related to Diabetes in the Chinese Population: The InterASIA Study

The objective was to compare central and overall obesity measurements for identifying diabetes mellitus (DM) and impaired fasting glucose (IFG) level in the Chinese population. Data for 15,236 Chinese adults between the ages of 35 and 74 years, obtained by the InterASIA Study in 2000-2001, were used for the current analyses. We analyzed the areas under the receiver operating characteristic (ROC) curves (AUCs) for waist circumference (WC), waist-to-hip ratio (WHR), and BMI to determine the ability of these indices to identify DM and IFG in the study sample and bootstrapped samples. WC was used as a measure of central obesity and BMI as a measure of overall obesity. The prevalence rates of central and overall obesity in the study population were 33.97% and 9.78%, respectively. The prevalence rates of IFG and DM were 7.34% and 5.51%, respectively. ROC analysis revealed significant differences between AUCs for WHR (0.666, 95% confidence interval, 0.647 to 0.685) and BMI (0.622, 95% confidence interval, 0.601 to 0.642) and for WC (0.661, 95% confidence interval, 0.643 to 0.682) and BMI for identifying DM (all p < 0.0001). The analysis also revealed significant differences between AUCs for WHR (0.638, 95% confidence interval, 0.619 to 0.655) and BMI (0.607, 95% confidence interval, 0.589 to 0.627) and for WC (0.637, 95% confidence interval, 0.615 to 0.654) and BMI for identifying IFG (all p < 0.001). Central obesity is more related to DM and IFG than is overall obesity in the Chinese population, and both WC and WHR are equally able to identify DM.

Obesity indices in relation to cardiovascular disease risk factors among young adult female students

The objective of the present study was to compare the percentage of body fat (%BF), BMI, and central fat distribution anthropometric measures as indices of obesity and to assess the respective associations with cardiovascular risk factors in young female students. Subjects were 220 healthy Greek female students. Dual-energy X-ray absorptiometry was used to estimate %BF, anthropometric measurements were obtained and blood samples were analysed for CVD risk factors. Results showed that 48.6 % of students had increased adiposity, while a considerable proportion was characterised by central fat distribution irrespective of the anthropometric index used. The proportion of subjects with at least one metabolic risk factor present was 60.4 %. Although %BF was not associated with any of the CVD risk factors, waist circumference, waist:hip ratio and waist:height ratio were all associated with CVD risk factors. Higher levels of these anthropometric variables demonstrated higher prevalence of CVD risk factors. The lack of association between %BF and CVD risk factors could be attributed to the fact that females with undesirable adiposity had a tendency for the gynaecoid type of obesity. In contrast, the present results suggest that central body fat distribution in young women may reflect increased risk due to high visceral and particularly intra-abdominal fat levels. Recent epidemiological data from Greece show a high prevalence of overweight and obesity in young adults. Therefore, assessing the risk for the presence of CVD risk factors is of particular importance. Central obesity anthropometric indices seem to be valuable screening tools for young women.

163 Do childhood BMI or skinfold adiposity measures predict physical activity in adolescents? A prospective longitudinal study

163 Do childhood BMI or skinfold adiposity measures predict physical activity in adolescents? A prospective longitudinal study

Eating Habits of 7-12 Year-Old Children in Tabriz, Iran

This study aimed to identify the eating habits of second and fifth graders from Tabriz, Iran. A total of 160 pupils were selected through random sampling at Oehit Sobhani Elementary School in the Kutb district of Tabriz. The sample consisted of 80 girls and 80 boys; 83 second graders and 78 fifth graders. Pupils’ BMI measures showed that 52.4% of the second graders and 46.2% of the fifth graders had normal physical structure. The results further suggested that the percentage of pupils who ate three meals per day was 60.6%. The most commonly skipped meal was breakfast (55.6%) and those who did have breakfast mostly preferred cheese and tea. Most pupils preferred meat dishes to vegetable dishes. It was thus concluded that pupils needed to be informed about the importance of breakfast and the requirements of a healthy diet.

Adolescent Perceptions of Their Diet Quality, Body Image, and Physical Activity Level: Comparison With Parent Perceptions

To compare actual measures of adolescent diet quality, BMI, and activity to their perceptions, and to their parents’ perceptions.

Monozygotic co-twin analyses of body composition measurements and serum lipids

Objective. To evaluate BMI and direct measures of body fat (BF) and lean body mass (LBM) in relation to fasting serum lipid profiles in a large Chinese population based twin sample using a monozygotic (MZ) co-twin analysis. Methods. Adiposity measures collected 1998–2000 on 987 MZ female 20–60 year old twin pairs ( n = 1974) included BMI, waist circumference (WC), waist/hip ratio (WHR), LBM, trunk fat (TF), %TF, total BF, and % total BF (measured by DEXA). Serum lipids included total cholesterol (TC), triglycerides (TG), LDL, and HDL. Co-twin analyses and conventional regression analyses were used to assess the association between individual adiposity and LBM measures, and serum lipids. Results. In this lean population with a mean BMI 21.8 (2.8), we observed considerable variability in adiposity measures and serum lipids. A positive linear association between all adiposity measures with LDL, TC, and TG, and a negative linear association with HDL was observed. A 1-unit z-score increase of adiposity measures, reflecting fat distribution, was associated with increases in (mmol/L) TC (0.063 to 0.164), LDL (0.064 to 0.131), TG (0.049 to 0.164), and a decrease in HDL (0.021 to 0.038) while controlling for matched factors within twin pairs (i.e., age and unmeasured confounders). However, similar associations were not observed for LBM. Conclusion. It is the BF (not LBM) that appears to be associated with serum lipid profiles. This study underscores that in populations where BMI is highly correlated with BF, BMI can be used as a surrogate for BF in evaluating risk of dyslipidemia. Otherwise, direct measures of BF are needed.

Body mass, DRD4, physical activity, sedentary behavior, and family socioeconomic status: the add health study.

To investigate the joint role of the 48-base pair repeat polymorphism of the dopamine receptor 4 gene (DRD4) and environmental factors in body mass variation among an ethnically diverse sample of U.S. adolescents and young adults. Approximately 2600 adolescent and young adults in the National Longitudinal Study of Adolescent Health (Add Health) who provided DNA measures and measures of height and weight were included in the analysis. Mixed regression modeling was used to investigate the effects of the 7R/7R and any5R variants in the DRD4 gene simultaneously with the effects of physical activity (PA), sedentary behavior (SB), and family socioeconomic status (SES) on body mass variation. European Americans, African Americans, and Hispanic Americans were modeled separately. Both the 7R/7R and any5R genotypes of the DRD4 gene were associated with age- and sex-specific BMI percentile score (BMI-P) based on the Centers for Disease Control and Prevention/National Center for Health Statistics 2000 reference curves among African Americans and only among African Americans (N = 413) 20 years old or younger. Neither genetic variants are associated with the BMI measure among white (N = 1386) and Hispanic-American (N = 331) adolescents. The presence of the 7R/7R genotype was associated with a reduction of 15.1 in BMI percentile (p = 0.005), and the presence of any5R was associated with an increase of 15.5 in BMI percentile (p = 0.003), after adjusting for PA, SB, and family SES. Neither PA nor SB as measured in Add Health is importantly associated with BMI-P, suggesting a complex relationship between body mass and PA/SB among adolescents and young adults. Family SES is negatively related to BMI-P in the European-American sample.

Cheap Donuts and Expensive Broccoli: The Effect of Relative Prices on Obesity

Americans have been getting fatter since at least the mid 1980s. To better understand this public health problem, much attention has been devoted to determining the underlying cause of increasing body weights in the U.S. We examine the role of relative food prices in determining an individual's body mass index, arguing that as healthful foods become more expensive relative to unhealthful foods, individuals substitute to a less healthful diet. Using data from the National Health Interview Survey (NHIS) for the period 1982-1996, we find that individual BMI measures, as well as the likelihood of being overweight or obese, exhibit a statistically significant positive correlation with the prices of healthful relative to unhealthful foods. These results are robust to endogenizing the relative price measure. While the magnitudes of our estimates suggest that relative price changes can only explain about 1 percent of the growth in BMI and the incidence of being overweight or obese over this period, they do provide some measure of how effective fat taxes would be in controlling the obesity epidemic. Our estimates imply, for example, that a 100 percent tax on unhealthful foods could reduce average BMI by about 1 percent, and the same tax could reduce the incidence of being overweight and the incidence of obesity by 2 percent and 1 percent respectively.

Body Mass Index and Risk of Suicide Among Men

Body mass index (BMI; calculated as weight in kilograms divided by height in meters squared) has been linked to depression and the risk of suicide attempts and deaths in conflicting directions. In a prospective cohort study of 46 755 men free of cancer enrolled in the Health Professionals Follow-up Study, participants reported their height, weight, diet, and physical activity on repeated occasions beginning in 1986 and were followed up until death or until February 2002. A subsample of 1829 men reported their mental health-related quality of life with the Mental Component Summary Scale of the 36-Item Short-Form Health Survey in 1998. A total of 131 men died from suicide during follow-up. A higher BMI was related to a graded decline in the suicide mortality rate, from 52 per 100 000 person-years among men with a BMI of less than 21 to 13 per 100 000 among men with a BMI of 30 or higher; the adjusted hazard ratio per 1-U BMI increment was 0.89 (95% confidence interval, 0.84-0.95; P<.001). The relationship was consistent when baseline or updated measures of BMI were used and with adjustment for medical illness, dietary factors, antidepressant use, physical activity, or social support. Height and physical activity were not strongly associated with risk. Analyses of mental health-related quality of life showed a similar positive relationship with BMI. Among men, risk of death from suicide is strongly inversely related to BMI, but not to height or to physical activity. Although obesity cannot be recommended on the basis of its detrimental effects, further research into the mechanisms of lower risk among overweight and obese men may provide insights into effective methods of suicide prevention.