GWAS for BMI: a treasure trove of fundamental insights into the genetic basis of obesity

Muller et al. [1] have provided a strong critique of the Genome-Wide Association Studies (GWAS) of body-mass index (BMI), arguing that the GWAS approach for the study of BMI is flawed, and has provided us with few biological insights. They suggest that what is needed instead is a new start, involving GWAS for more complex energy balance related traits. In this invited counter-point, we highlight the substantial advances that have occurred in the obesity field, directly stimulated by the GWAS of BMI. We agree that GWAS for BMI is not perfect, but consider that the best route forward for additional discoveries will likely be to expand the search for common and rare variants linked to BMI and other easily obtained measures of obesity, rather than attempting to perform new, much smaller GWAS for energy balance traits that are complex and expensive to measure. For GWAS in general, we emphasise that the power from increasing the sample size of a crude but easily measured phenotype outweighs the benefits of better phenotyping.

Social status and energy intake: a randomized controlled experiment

While the inverse association between socioeconomic status (SES) and obesity in high gross domestic product countries is well established using observational data, the extent to which the association is due to a true causal effect of SES and, if so, the mechanisms of this effect remain incompletely known. To assess the influence of social status on obesity via energy intake, we randomized individuals to a higher or lower social status and observed subsequent energy intake. College students between the ages of 18 and 25 were randomized to social status and were operationalized as being a leader or follower in a partner activity as purportedly determined by a (bogus) test of leadership ability. Investigators were blinded to treatment assignment. Immediately after being told their leadership assignment, paired participants were provided with platters of food. Energy intake was objectively measured in kilocalories (kcal) consumed, and paired t-tests were used to test for significant differences in intake between leaders and followers. A total of 60 participants were included in the final analysis (males = 28, females = 32). Overall, no difference in energy intake was observed between leaders and followers, consuming an average of 575.3 and 579.8 kcal, respectively (diff = 4.5 kcal, P = 0.94). The null hypothesis of no effect of social status, operationalized as assignment to a leadership position in a small-group activity, on energy intake was not rejected.

Oxidative costs of reproduction: Oxidative stress in mice fed standard and low antioxidant diets

Lactation is one of the most energetically expensive behaviours, and trade-offs may exist between the energy devoted to it and somatic maintenance, including protection against oxidative damage. However, conflicting data exist for the effects of reproduction on oxidative stress. In the wild, a positive relationship is often observed, but in laboratory studies oxidative damage is often lower in lactating than in non-breeding animals. We hypothesised that this discrepancy may exist because during lactation food intake increases many-fold resulting in a large increase in the intake of dietary antioxidants which are typically high in laboratory rodent chow where they are added as a preservative. We supplied lactating and non-breeding control mice with either a standard or low antioxidant diet and studied how this affected the activity of endogenous antioxidants (catalase, superoxide dismutase; SOD, and glutathione peroxidise; GPx) and oxidative damage to proteins (protein carbonyls, PC) in liver and brain tissue. The low antioxidant diet did not significantly affect activities of antioxidant enzymes in brain or liver, and generally did not result in increased protein damage, except in livers of control mice on low antioxidant diet. Catalase activity, but not GPx or SOD, was decreased in both control and lactating mice on the low antioxidant diet. Lactating mice had significantly reduced oxidative damage to both liver and brain compared to control mice, independent of the diet they were given. In conclusion, antioxidant content of the diet did not affect oxidative stress in control or reproductive mice, and cannot explain the previously observed reduction in oxidative stress in lactating mammals studied in the laboratory. The reduced oxidative stress in the livers of lactating mice even under low antioxidant diet treatment was consistent with the 'shielding' hypothesis.

The importance of prediction model validation and assessment in obesity and nutrition research

Deriving statistical models to predict one variable from one or more other variables, or predictive modeling, is an important activity in obesity and nutrition research. To determine the quality of the model, it is necessary to quantify and report the predictive validity of the derived models. Conducting validation of the predictive measures provides essential information to the research community about the model. Unfortunately, many articles fail to account for the nearly inevitable reduction in predictive ability that occurs when a model derived on one data set is applied to a new data set. Under some circumstances, the predictive validity can be reduced to nearly zero. In this overview, we explain why reductions in predictive validity occur, define the metrics commonly used to estimate the predictive validity of a model (for example, coefficient of determination (R(2)), mean squared error, sensitivity, specificity, receiver operating characteristic and concordance index) and describe methods to estimate the predictive validity (for example, cross-validation, bootstrap, and adjusted and shrunken R(2)). We emphasize that methods for estimating the expected reduction in predictive ability of a model in new samples are available and this expected reduction should always be reported when new predictive models are introduced.

Rigorous control conditions diminish treatment effects in weight loss-randomized controlled trials

BACKGROUND

It has not been established whether control conditions with large weight losses (WLs) diminish expected treatment effects in WL or prevention of weight gain (PWG)-randomized controlled trials (RCTs).

SUBJECTS/METHODS

We performed a meta-analysis of 239 WL/PWG RCTs that include a control group and at least one treatment group. A maximum likelihood meta-analysis framework was used to model and understand the relationship between treatment effects and control group outcomes.

RESULTS

Under the informed model, an increase in control group WL of 1 kg corresponds with an expected shrinkage of the treatment effect by 0.309 kg (95% confidence interval (-0.480, -0.138), P=0.00081); this result is robust against violations of the model assumptions.

CONCLUSIONS

We find that control conditions with large WLs diminish expected treatment effects. Our investigation may be helpful to clinicians as they design future WL/PWG studies.

A systematic review and meta-analysis of randomized controlled trials of the impact of sleep duration on adiposity and components of energy balance

Recent epidemiological and ecological trends in humans indicate a possible causal relationship between sleep duration and energy balance. We aimed to find experimental evidence that has tested this relationship between sleep duration and measures of body composition, food intake or biomarkers related to food intake. We conducted a systematic literature review using six databases throughout 7 August 2014. We sought reports of randomized controlled trials where sleep duration was manipulated and measured outcomes were body weight or other body composition metrics, food intake, and/or biomarkers related to eating. We found 18 unique studies meeting all criteria: eight studies with an outcome of body weight (4 - increased sleep, 4 - reduced sleep); four studies on food intake; four studies of sleep restriction on total energy expenditure and three of respiratory quotient; and four studies on leptin and/or ghrelin. Few controlled experimental studies have addressed the question of the effect of sleep on body weight/composition and eating. The available experimental literature suggests that sleep restriction increases food intake and total energy expenditure with inconsistent effects on integrated energy balance as operationalized by weight change. Future controlled trials that examine the impact of increased sleep on body weight/energy balance factors are warranted.

Energy balance measurement: when something is not better than nothing

Energy intake (EI) and physical activity energy expenditure (PAEE) are key modifiable determinants of energy balance, traditionally assessed by self-report despite its repeated demonstration of considerable inaccuracies. We argue here that it is time to move from the common view that self-reports of EI and PAEE are imperfect, but nevertheless deserving of use, to a view commensurate with the evidence that self-reports of EI and PAEE are so poor that they are wholly unacceptable for scientific research on EI and PAEE. While new strategies for objectively determining energy balance are in their infancy, it is unacceptable to use decidedly inaccurate instruments, which may misguide health-care policies, future research and clinical judgment. The scientific and medical communities should discontinue reliance on self-reported EI and PAEE. Researchers and sponsors should develop objective measures of energy balance.

Randomized controlled trial examining expectancy effects on the accuracy of weight measurement

BACKGROUND

Researchers and participants' expectations can influence treatment response. Less is known about the effects of researchers' expectations on the accuracy of data collection in the context of a weight loss trial.

METHODS

Student raters (N = 58; age = 20.1 ± 2.3 years) were recruited to weigh individuals who they thought were completing a 12-month weight loss trial, although these 'participants' were actually standardized patients (SPs) playing these roles. Prior to data collection, student raters were provided information suggesting that the tested treatment had been effective. Each student rater received a list of 9-10 'participants' to weigh. While the list identified each person as 'treatment' or 'control', this assignment was at random, which allowed us to examine the effects of non-blinding and expectancy manipulation on weight measurement accuracy. We hypothesized that raters would record the weights of 'treatment participants' as lower than those of 'control participants'.

RESULTS

Contrary to our hypothesis, raters recorded weights that were 0.293 kg heavier when weighing 'treatment' vs. 'control' SPs, although this difference was not significant (P = 0.175).

CONCLUSIONS

This pilot study found no evidence that manipulating expectancies about treatment efficacy or not blinding raters biased measurements. Future work should examine other biases which may be created by not blinding research staff who implement weight loss trials as well as the participants in those trials.

Predicting adult weight change in the real world: a systematic review and meta-analysis accounting for compensatory changes in energy intake or expenditure

BACKGROUND

Public health and clinical interventions for obesity in free-living adults may be diminished by individual compensation for the intervention. Approaches to predict weight outcomes do not account for all mechanisms of compensation, so they are not well suited to predict outcomes in free-living adults. Our objective was to quantify the range of compensation in energy intake or expenditure observed in human randomized controlled trials (RCTs).

METHODS

We searched multiple databases (PubMed, CINAHL, SCOPUS, Cochrane, ProQuest, PsycInfo) up to 1 August 2012 for RCTs evaluating the effect of dietary and/or physical activity interventions on body weight/composition.

INCLUSION CRITERIA

subjects per treatment arm ≥5; ≥1 week intervention; a reported outcome of body weight/body composition; the intervention was either a prescribed amount of over- or underfeeding and/or supervised or monitored physical activity was prescribed; ≥80% compliance; and an objective method was used to verify compliance with the intervention (for example, observation and electronic monitoring). Data were independently extracted and analyzed by multiple reviewers with consensus reached by discussion. We compared observed weight change with predicted weight change using two models that predict weight change accounting only for metabolic compensation.

FINDINGS

Twenty-eight studies met inclusion criteria. Overfeeding studies indicate 96% less weight gain than expected if no compensation occurred. Dietary restriction and exercise studies may result in up to 12-44% and 55-64% less weight loss than expected, respectively, under an assumption of no behavioral compensation.

INTERPRETATION

Compensation is substantial even in high-compliance conditions, resulting in far less weight change than would be expected. The simple algorithm we report allows for more realistic predictions of intervention effects in free-living populations by accounting for the significant compensation that occurs.

Association of basketball season with body composition in elite junior players

AIM

Body composition changes among elite athletes may influence competitive performance. This study aimed to characterize the body composition changes at the molecular, cellular, tissue, and whole-body level of analysis in elite junior basketball players during the course of a season.

METHODS

Twelve males and 11 females (16 to 17 years) were evaluated. Dual-energy X-ray absorptiometry (DXA) was used to assess bone mineral (Mo) and lean-soft tissue (LST). Total-body water (TBW) and extracellular water (ECW) were assessed using isotope dilution techniques, and extracellular (ECF) and intracellular fluids (ICF) were calculated. Fat mass (FM) and fat-free mass (FFM) were assessed with a four-compartment model. Body cell mass was calculated (LST - (ECF + ECS)). Skeletal muscle (SM) was estimated using appendicular LST (ALST) as: (1.19 x ALST) - 1.65. At the whole-body level, weight, sum of 7 skinfolds, and muscle circumferences (Mc) were measured. The handgrip and the countermovement jump tests were used for performance assessment.

RESULTS

Males increased FFM (4.4±2.3%), TBW (3.5±4.6%), SM (4.5±2.3%), and arm (3.4±2.7%) and thigh (3.8±3%) Mc. Females increased SM (5.9±4.6%) and arm (3.6±3.8%) and thigh (4±5.2%) Mc and decreased ICF (-9.7±13.6%). FFM components differed from the established values based on cadaver analysis. Both genders increased their performance and associations were found between changes in molecular and whole-body components with performance.

CONCLUSION

In conclusion the season was associated with an improved body composition profile in males and few changes in females.

Interleukin-8 and interleukin-10, brain volume and microstructure, and the influence of calorie restriction in old rhesus macaques

Higher systemic levels of the proinflammatory cytokine interleukin-6 (IL-6) were found to be associated with lower gray matter volume and tissue density in old rhesus macaques. This association between IL-6, and these brain indices were attenuated by long-term 30 % calorie restriction (CR). To extend these findings, the current analysis determined if a CR diet in 27 aged rhesus monkeys compared to 17 normally fed controls reduced circulating levels of another proinflammatory cytokine, interleukin-8 (IL-8), and raised levels of anti-inflammatory interleukin-10 (IL-10). Further, these cytokines were regressed onto imaged brain volume and microstructure using voxel-wise regression analyses. CR significantly lowered IL-8 and raised IL-10 levels. Across the two dietary conditions, higher IL-8 predicted smaller gray matter volumes in bilateral hippocampus. Higher IL-10 was associated with more white matter volume in visual areas and tracts. Consuming a CR diet reduced the association between systemic IL-8 and hippocampal volumes. Conversely, CR strengthened associations between IL-10 and microstructural tissue density in the prefrontal cortex and other areas, particularly in a region of dorsal prefrontal cortex, which concurred with our prior findings for IL-6. Consumption of a CR diet lowered proinflammatory and increased anti-inflammatory cytokine concentrations, which lessened the statistical association between systemic inflammation and the age-related alterations in important brain regions, including the hippocampus.

Will reducing sugar-sweetened beverage consumption reduce obesity? Evidence supporting conjecture is strong, but evidence when testing effect is weak

We provide arguments to the debate question and update a previous meta-analysis with recently published studies on effects of sugar-sweetened beverages (SSBs) on body weight/composition indices (BWIs). We abstracted data from randomized controlled trials examining effects of consumption of SSBs on BWIs. Six new studies met these criteria: (i) human trials, (ii) ≥ 3 weeks duration, (iii) random assignment to conditions differing only in consumption of SSBs and (iv) including a BWI outcome. Updated meta-analysis of a total of seven studies that added SSBs to persons' diets showed dose-dependent increases in weight. Updated meta-analysis of eight studies attempting to reduce SSB consumption showed an equivocal effect on BWIs in all randomized subjects. When limited to subjects overweight at baseline, meta-analysis showed a significant effect of roughly 0.25 standard deviations (more weight loss/less weight gain) relative to controls. Evidence to date is equivocal in showing that decreasing SSB consumption will reduce the prevalence of obesity. Although new evidence suggests that an effect may yet be demonstrable in some populations, the integrated effect size estimate remains very small and of equivocal statistical significance. Problems in this research area and suggestions for future research are highlighted.

Empirical evidence does not support an association between less ambitious pre-treatment goals and better treatment outcomes: a meta-analysis

Setting realistic weight loss goals may play a role in weight loss. We abstracted data from randomized controlled trials and observational studies conducted between 1998 and 2012 concerning the association of weight loss goals with weight loss. Studies included those that (i) were conducted in humans; (ii) delivered a weight loss intervention; (iii) lasted ≥6 weeks; (iv) assessed baseline weight loss goals; (vi) assessed pre- and post-weight either in the form of body mass index or some other measure that could be converted to weight loss based on information included in the original study or later provided by the author(s); and (vii) assessed the correlation between weight loss goals and final weight loss or provided data to calculate the correlation. Studies that included interventions to modify weight loss goals were excluded. Eleven studies met inclusion criteria. The overall correlation between goal weight and weight at intervention completion was small and statistically insignificant (ρ=0.0 5 ; P = 0.20). The current evidence does not demonstrate that setting realistic goals leads to more favourable weight loss outcomes. Thus, our field may wish to reconsider the value of setting realistic goals in successful weight loss.

Can Ethnic Differences in Men's Preferences for Women's Body Shapes Contribute to Ethnic Differences in Female Adiposity?

In the United States, obesity is more common among black and Hispanic than white women. One putative cause of this difference is different cultural norms for attractiveness. Two studies assessed ethnic differences in men's perceptions of the attractiveness of females of varying sizes. In the first, 108 men recruited on the New York subway were shown sets of silhouettes depicting female bodies varying in fatness and were asked to pick the silhouette they found most attractive. They were also asked to indicate the thinnest and fattest figures they would consider dating. A measure of "latitude of acceptance" was computed as the difference between the thinnest and fattest figures considered. Results indicated no relationship between ethnicity and preference (F = 1.383, p = .257) or "latitude" (F = .102, p = .903). In Study 2, "personal advertisements" placed by 373 black, 1915 white, 110 Hispanic, and 30 Asian men from 35 newspapers and magazines were coded as: 1) thinness preferred; 2) no information on weight preference; 3) fatness preferred; or 4) states weight or looks unimportant. Results indicated a statistically significant but small association between ethnicity and preference (chi2 = 49.55, df = 9, p < .00001). Relative to white and Asian men, black and Hispanic men more frequently requested fat women, Hispanic men less frequently requested thin women, and black men more frequently stated that looks or weight did not matter. Ethnicity explained only 2.1% of the variance in preference. Thus, it seems unlikely that ethnic differences in men's preferences for women's body shapes contribute substantially to ethnic differences in female adiposity.

Evidence of Commingling in Human Eating Behavior

This investigation tested whether distributions of certain aspects of eating behavior were consistent with the notion of a "mixture model;" that is, two or more distinct commingled component distributions, consistent with the possibility of major gene action. Undergraduates (n=901) completed self-report trait measures of hunger, disinhibition, and dietary restraint. Variables were residualized for gender and age and transformed to remove skewness. Residualized transformed distributions were tested for departure from unimodality with Hartigan's dip statistic. The distributions of all three aspects of eating behavior were significantly non-unimodal. Next, component multivariate normal distributions were estimated via maximum likelihood. Likelihood ratio tests were employed to compare nested models. A mixture of four distributions with unequal variance-covariance matrices fit significantly better than any more parsimonious model. In sum, these data strongly suggest that the distributions of several measures of eating behavior are composed of four component distributions. This finding is consistent with the possibility of major gene effects for eating behavior.

Relationships of percent body fat and percent trunk fat with bone mineral density among Chinese, black, and white subjects

We examined ethnic difference in the association of body fat and trunk fat with bone mineral density (BMD) among Chinese, white, and black subjects. We found that, with greater body and trunk fat, both white and black subjects were more likely to have a low BMD than Chinese subjects.

INTRODUCTION

Ethnic differences in body fat, abdominal fat distribution, and BMD have been found in previous studies between Chinese and white subjects. However, the associations of body fat and abdominal fat distribution with BMD have not been studied, and whether the ethnic differences have an effect on these associations is unclear.

METHODS

We evaluated 1,147 subjects aged ≥ 18 years (805 Chinese, 193 whites, and 149 blacks). Percent body fat (%BF), percent trunk fat (%TF), and total and regional BMD including that of head, arm, leg, trunk, rib, spine, and pelvis were measured by dual-energy X-ray absorptiometry. Linear regression models were developed to test the association of ethnicity, %BF, and interaction between ethnicity and %BF with BMD. The models were repeated again, replacing %BF with %TF.

RESULTS

Chinese subjects showed lower BMD in total and most regions compared with black and white subjects; however, these differences were eliminated between Chinese and whites within both sexes and between Chinese and black men when age, weight, height, and %BF were added. %BF and %TF were negatively associated with most regional body BMD. The interactions between %BF, %TF, and ethnicity were found in most regional body BMD among Chinese, white, and black subjects for both men and women.

CONCLUSION

Both %BF and %TF have negative associations with BMD. With greater accumulation of %BF and %TF, both white and black subjects may experience a higher risk of low BMD than Chinese subjects.

Is funding source related to study reporting quality in obesity or nutrition randomized control trials in top-tier medical journals?

BACKGROUND

Faithful and complete reporting of trial results is essential to the validity of the scientific literature. An earlier systematic study of randomized controlled trials (RCTs) found that industry-funded RCTs appeared to be reported with greater quality than non-industry-funded RCTs. The aim of this study was to examine the association between systematic differences in reporting quality and funding status (that is, industry funding vs non-industry funding) among recent obesity and nutrition RCTs published in top-tier medical journals.

METHODS

Thirty-eight obesity or nutrition intervention RCT articles were selected from high-profile, general medical journals (The Lancet, Annals of Internal Medicine, JAMA and the British Medical Journal) published between 2000 and 2007. Paired papers were selected from the same journal published in the same year, one with and the other without industry funding. The following identifying information was redacted: journal, title, authors, funding source and institution(s). Then three raters independently and blindly rated each paper according to the Chalmers method, and total reporting quality scores were calculated.

FINDINGS

The inter-rater reliability (Cronbach's alpha) was 0.82 (95% confidence interval = 0.80-0.84). The total mean (M) and s.d. of Chalmers Index quality score (out of a possible 100) for industry-funded studies were M = 84.5, s.d. = 7.04 and for non-industry-funded studies they were M = 79.4, s.d. = 13.00. A Wilcoxon matched-pairs signed-ranks test indicates no significant rank difference in the distributions of total quality scores between funding sources, Z = -0.966, P = 0.334 (two tailed).

INTERPRETATION

Recently published RCTs on nutrition and obesity that appear in top-tier journals seem to be equivalent in quality of reporting, regardless of funding source. This may be a result of recent reporting of quality statements and efforts of journal editors to raise all papers to a common standard.

Meta-analysis of studies of a specific delivery mode for a modified-carbohydrate diet

BACKGROUND

Obesity is highly prevalent throughout the world. Although modified-carbohydrate diets (MCDs) comprise one popular approach, questions remain about their utility for weight loss. The objective of the present study was to conduct a meta-analysis of randomised controlled trials (RCTs) of a specific MCD compared with various control diets on weight loss.

METHODS

Data from four RCTs (three obtained from the sponsor and one indentified through literature searches) were included. Intent-to-treat analyses were conducted using multiple imputation to handle missing data, where possible. Because inter-study heterogeneity was demonstrated with fixed-effects meta-analysis, a random-effects meta-analysis also was conducted.

RESULTS

When considered separately, all four studies showed greater reduction in body weight with the MCD compared to control diets at 12-week follow-up; the results at 24 weeks (available for three of the studies) were not as consistent. Results for body mass index (BMI) were similar. Greater reductions in waist circumference with the MCD were seen at either time point in only one study. When fixed-effects meta-analysis was applied, significantly greater reductions in weight, BMI and waist circumference with the MCD at both 12 weeks (1.66 kg, 0.53 kg m(-2) and 1.02 cm, respectively) and 24 weeks (1.20 kg, 0.43 kg m(-2) and 0.69 cm, respectively) were evident. Random-effects meta-analysis revealed similar results; however, the 24-week difference for a reduction in waist circumference was no longer statistically significant.

CONCLUSIONS

Meta-analysis of individual RCT results demonstrated consistent benefits of this MCD compared to control diets on weight loss up to 24 weeks and waist circumference up to 12 weeks.

Nutritively sweetened beverage consumption and body weight: a systematic review and meta-analysis of randomized experiments

Nutritively sweetened beverages (NSBs) may play a role in the obesity epidemic. We abstracted data from randomized controlled trials (RCTs) and evidence-based reviews through January 2009 concerning effects of consumption of NSBs on changes in body weight and adiposity. Studies included were those (i) conducted in humans; (ii) lasting at least 3 weeks; (iii) incorporating random assignment of subjects to conditions that differed only in the consumption of NSBs and (iv) including an adiposity indicator as an outcome. Twelve studies met the inclusion criteria. Meta-analysis of six studies that added NSBs to persons' diets showed dose-dependent increases in weight. Contrarily, meta-analysis of studies that attempted to reduce NSB consumption consistently showed no effect on body mass index (BMI) when all subjects were considered. Meta-analysis of studies providing access to results separately for subjects overweight at baseline showed a significant effect of a roughly 0.35 standard deviations lesser BMI change (i.e. more weight loss or less weight gain) relative to controls. The current evidence does not demonstrate conclusively that NSB consumption has uniquely contributed to obesity or that reducing NSB consumption will reduce BMI levels in general. We recommend an adequately powered RCT with overweight persons, for whom there is suggestive evidence of an effect.

Genetic diversity of plaque mutans streptococci with rep-PCR

Mutans streptococci (MS) are key organisms associated with the etiology of dental caries. Using probabilities that were tested by oversampling, we designed this study to determine the minimal number of MS isolates from an individual required to evaluate diversity of genotypes. MS isolates were genotyped by repetitive extragenic palindromic-polymerase chain-reaction (rep-PCR). Analysis of 20 isolates from individuals resulted in a mean of 1.6 and 2.4 genotypes in children (N = 12) and adults (N = 10), respectively. In a follow-up study, reducing the number of isolates to 7-10 resulted in a theoretical probability of up to 78% for detecting up to 4 genotypes. A mean of 1.5 genotypes was found in 35 children and 10 adults. These findings provide evidence for the design of studies of MS genotyping that can serve as a model for the analysis of genotypes within individuals.

Getting carried away: a note showing baseline observation carried forward (BOCF) results can be calculated from published complete-cases results

OBJECTIVE

Randomized controlled trials (RCTs) in obesity are plagued by missing data due to participant dropouts. Most methodologists and regulatory bodies agree that the primary analysis of such RCTs should be based on the intent-to-treat (ITT) principle, such that all randomized subjects are included in the analysis, even those who dropped out. Unfortunately, some authors do not include an ITT analysis in their published reports. Here we show that one form of ITT analysis, baseline observation carried forward (BOCF), can be performed utilizing only information available in a published complete-case (CC) analysis, permitting readers, editors, meta-analysts and regulators to easily conduct their own ITT analyses when the original authors do not report one.

METHOD

We mathematically derive a simple method for estimating and testing treatment effects using the BOCF to allow a more conservative comparison of treatment effects when there are dropouts in a clinical trial. We provide two examples of this method using available CC analysis data from reported obesity trials to illustrate the application for readers who wish to determine a range of treatment effects based on published summary statistics.

CONCLUSION

Commonly used CC analyses may lead to inflated type I error rates and/or treatment effect estimates. The method described herein can be useful for researchers who wish to estimate a conservative range of plausible treatment effects based on limited reported data. Limitations of this method are discussed.

Predictive ability of subsets of single nucleotide polymorphisms with and without parent average in US Holsteins

Genome-enabled prediction of breeding values using high-density panels (HDP) can be highly accurate, even for young sires. However, the cost of the assay may limit its use to elite animals only. Low-density panels (LDP) containing a subset of single nucleotide polymorphisms (SNP) may give reasonably accurate predictions and could be used cost-effectively with young males and females. This study evaluates strategies for selecting subsets of SNP for several traits, compares predictive ability of LDP with that of HDP, and assesses the benefits of including parent average (PA) as a predictor in models using LDP. Data consisting of progeny-test predicted transmitting ability (PTA) for net merit and 6 other traits of economic interest from 4,783 Holstein sires were evaluated using testing and training sets with regressions on their high-density genotypes and parent averages for net merit index. Additionally, SNP subsets of different sizes were selected using different strategies, including the "best" SNP based on the absolute values of their estimated effects from HDP models for either the trait itself or lifetime net merit, and evenly spaced (ES) SNP across the genome. Overall, HDP models had the best predictive ability, setting an upper bound for the predictive ability of LDP sets. Low-density panels targeting the SNP with strongest effects (for either a single trait or lifetime net merit) provided reasonably accurate predictions and generally outperformed predictions based on evenly spaced SNP. For example, evenly spaced sets would require at least 5,000 to 7,500 SNP to reach 95% of the predictive ability provided by HDP. On the other hand, this level of predictive ability can be achieved with sets of 2,000 SNP when SNP are selected based on magnitude of estimated effects for the trait. Accuracy of predictions based on LDP can be improved markedly by including parent average as a fixed effect in the model; for example, a set with the 1,000 best SNP using the parent average achieved the 95% of the accuracy of a HDP model.

Obesity and non-fatal motor vehicle crash injuries: sex difference effects

Background

Obesity and motor vehicle crash (MVC) injuries are two parallel epidemics in the United States. An important unanswered question is if there are sex differences in the associations between the presence of obesity and non-fatal MVC injuries.

Objectives

To further understand the association between obesity and non-fatal motor vehicle crash injuries, particularly the sex differences in these relations.

Methods

We examined this question by analyzing data from the 2003 to 2007 National Automotive Sampling System Crashworthiness Data System (NASS CDS). A total of 10, 962 drivers who were aged 18 years or older and who survived frontal collision crashes were eligible for study.

Results

Male drivers experienced a lower rate of overall non-fatal MVC injuries than did female drivers (38.1% vs. 52.2%) but a higher rate of severe injuries (0.7% vs. 0.2%). After adjusting for change in velocity (ΔV) during the crashes, obese male drivers showed a much higher risk [logistic coefficients of BMI for moderate, serious, and severe injury are 0.0766, 0.1470, and 0.1792, respectively; all p<0.05] of non-fatal injuries than did non-obese male drivers and these risks increased with injury severity. Non-fatal injury risks were not found to be increased in obese female drivers. The association between obesity and risk of non-fatal injury was much stronger for male drivers than for female drivers.

Conclusion

The higher risk of non-fatal MVC injuries in obese male drivers might result from their different body shape and fat distribution compared with obese female drivers. Our findings should be considered for obesity reduction, traffic safety evaluation and vehicle design for obese male drivers and provide testable hypotheses for future studies.

No compelling evidence that sibutramine prolongs life in rodents despite providing a dose-dependent reduction in body weight

OBJECTIVE

The health and longevity effects of body weight reduction resulting from exercise and caloric restriction in rodents are well known, but less is known about whether similar effects occur with weight reduction from the use of a pharmaceutical agent such as sibutramine, a serotonin-norepinephrine reuptake inhibitor.

RESULTS AND CONCLUSION

Using data from a 2-year toxicology study of sibutramine in Sprague-Dawley CD rats and CD-1 mice, despite a dose-dependent reduction in food intake and body weight in rats compared with controls, and a body weight reduction in mice at the highest dose, there was no compelling evidence for reductions in mortality rate.

Use of self-reported height and weight biases the body mass index-mortality association

Background

Many large-scale epidemiologic data sources used to evaluate the body mass index (BMI: kg/m²) mortality association have relied on BMI derived from self-reported height and weight. Although measured BMI (BMI_M) and self-reported BMI (BMI_SR) correlate highly, self-reports are systematically biased.

Objective

To rigorously examine how self-reporting bias influences the association between BMI and mortality rate.

Subjects

Samples representing the US non-institutionalized civilian population.

Design and Methods

National Health and Nutrition Examination Survey data (NHANES II: 1976-80; NHANES III: 1988-94) contain BMI_M and BMI_SR. We applied Cox regression to estimate mortality hazard ratios (HRs) for BMI_M and BMI_SR categories, respectively, and compared results. We similarly analyzed subgroups of ostensibly healthy never-smokers.

Results

Misclassification by BMI_SR among the underweight and obesity ranged from 30–40% despite high correlations between BMI_M and BMI_SR (r>0.9). The reporting bias was moderately correlated with BMI_M (r>0.35), but not BMI_SR (r<0.15). Analyses using BMI_SR failed to detect six of eight significant mortality HRs detected by BMI_M. Significantly biased HRs were detected in the NHANES II full dataset (χ² = 12.49; p = 0.01) and healthy subgroup (χ² = 9.93; p = 0.04), but not in the NHANES III full dataset (χ² = 5.63; p = 0.23) or healthy subgroup (χ² = 1.52; p = 0.82).

Conclusions

BMI_SR should not be treated as interchangeable with BMI_M in BMI-mortality analyses. Bias and inconsistency introduced by using BMI_SR in place of BMI_M in BMI-mortality estimation and hypothesis tests may account for important discrepancies in published findings.

White hat bias: examples of its presence in obesity research and a call for renewed commitment to faithfulness in research reporting

`White hat bias' (WHB) (bias leading to distortion of information in the service of what may be perceived to be righteous ends) is documented via quantitative data and anecdotal evidence from the research record regarding the postulated predisposing and protective effects respectively of nutritively-sweetened beverages and breastfeeding on obesity. Evidence of an apparent WHB is found in a degree sufficient to mislead readers. WHB bias may be conjectured to be fuelled by feelings of righteous zeal, indignation toward certain aspects of industry, or other factors. Readers should beware of WHB and our field should seek methods to minimize it.

Genetic and environmental contributions to body mass index: comparative analysis of monozygotic twins, dizygotic twins and same-age unrelated siblings

BACKGROUND

Earlier studies have established that a substantial percentage of variance in obesity-related phenotypes is explained by genetic components. However, only one study has used both virtual twins (VTs) and biological twins and was able to simultaneously estimate additive genetic, non-additive genetic, shared environmental and unshared environmental components in body mass index (BMI). Our current goal was to re-estimate four components of variance in BMI, applying a more rigorous model to biological and virtual multiples with additional data. Virtual multiples share the same family environment, offering unique opportunities to estimate common environmental influence on phenotypes that cannot be separated from the non-additive genetic component using only biological multiples.

METHODS

Data included 929 individuals from 164 monozygotic twin pairs, 156 dizygotic twin pairs, five triplet sets, one quadruplet set, 128 VT pairs, two virtual triplet sets and two virtual quadruplet sets. Virtual multiples consist of one biological child (or twins or triplets) plus one same-aged adoptee who are all raised together since infancy. We estimated the additive genetic, non-additive genetic, shared environmental and unshared random components in BMI using a linear mixed model. The analysis was adjusted for age, age(2), age(3), height, height(2), height(3), gender and race.

RESULTS

Both non-additive genetic and common environmental contributions were significant in our model (P-values<0.0001). No significant additive genetic contribution was found. In all, 63.6% (95% confidence interval (CI) 51.8-75.3%) of the total variance of BMI was explained by a non-additive genetic component, 25.7% (95% CI 13.8-37.5%) by a common environmental component and the remaining 10.7% by an unshared component.

CONCLUSION

Our results suggest that genetic components play an essential role in BMI and that common environmental factors such as diet or exercise also affect BMI. This conclusion is consistent with our earlier study using a smaller sample and shows the utility of virtual multiples for separating non-additive genetic variance from common environmental variance.

Critical review of the World Health Organization's (WHO) 2007 report on 'evidence of the long-term effects of breastfeeding: systematic reviews and meta-analysis' with respect to obesity

Obesity among children and adults has become a highly recognized public health concern and there is an increasing need to discover causes and evaluate preventative measures. One putatively causal influence on obesity is breastfeeding (BF). The World Health Organization (WHO) recently published a report (WR) on 'Evidence of the Long-Term Effects of Breastfeeding: Systematic Reviews and Meta-Analysis' and concluded 'that the evidence suggests that breastfeeding may have a small protective effect[emphasis added] on the prevalence of obesity . . . [and] the effect of breastfeeding was not likely to be due to publication bias or confounding.' Here we provide a critical overview of the WR's section on BF and obesity by addressing eight questions: Q1: Is there sufficient evidence to conclude that BF is associated with lower rates of obesity in children? Q2: Is there sufficient evidence to conclude that BF is associated with lower rates of obesity among breastfed offspring once they reach adulthood? Q3: If there are such associations, what are their magnitudes in comparison with other putatively causal factors and with respect to the potential impact on individual or population levels of obesity? Q4: Is there sufficient evidence to conclude that BF causes a reduction in risk of obesity during childhood? Q5: Is there sufficient evidence to conclude that BF does not cause a reduction in risk of obesity during childhood? Q6: Is there sufficient evidence to conclude that BF causes a long-term reduction in risk of obesity that persists into adulthood? Q7: Is there sufficient evidence to conclude that BF does not cause a long-term reduction in risk of obesity that persists into adulthood? Q8: What further research might be done to address these questions? We conclude that, while BF may have benefits beyond any putative protection against obesity, and benefits of BF most likely outweigh any harms, any statement that a strong, clear or consistent body of evidence shows that BF causally reduces the risk of overweight or obesity is unwarranted at this time.

Industry funding and the reporting quality of large long-term weight loss trials

BACKGROUND

Quality of reporting (QR) in industry-funded research is a concern of the scientific community. Greater scrutiny of industry-sponsored research reporting has been suggested, although differences in QR by sponsorship type have not been evaluated in weight loss interventions.

OBJECTIVE

To evaluate the association of funding source and QR of long-term obesity randomized clinical trials (RCT).

METHODS

We analysed papers that reported long-term weight loss trials. Articles were obtained through searches of Medline, HealthStar, and the Cochrane Controlled Trials Register between the years 1966 and 2003. QR scores were determined for each study based upon expanded criteria from the Consolidated Standards for Reporting Trials (CONSORT) checklist for a maximum score of 44 points. Studies were coded by category of industry support (0=no industry support, 1=industry support, 2=in kind contribution from industry and 3=duality of interest reported). Individual CONSORT reporting criteria were tabulated by funding type. An independent samples t-test compared the differences in QR scores by funding source and the Wilcox-Mann-Whitney test and generalised estimating equations (GEE) were used for sensitivity analyses.

RESULTS

Of the 63 RCTs evaluated, 67% were industry-supported trials. Industry funding was associated with higher QR score in long-term weight loss trials compared with nonindustry-funded studies (mean QR (s.d.): industry=27.9 (4.1), nonindustry=23.4 (4.1); P<0.0005). The Wilcox-Mann-Whitney test confirmed this result (P<0.0005). Controlling for the year of publication and whether the paper was published before the CONSORT statement was released in the GEE regression analysis, the direction and magnitude of effect were similar and statistically significant (P=0.035). Of the individual criteria that prior research has associated with biases, industry funding was associated with greater reporting of intent-to-treat analysis (P=0.0158), but was not different from nonindustry studies in reporting of treatment allocation and blinding.

CONCLUSION

Our findings suggest that the efforts to improve reporting quality be directed to all obesity RCTs, irrespective of funding source.

The potential role of soyfoods in weight and adiposity reduction: an evidence-based review

Evidence concerning the relationship between soyfoods and weight loss was reviewed. Detailed searches of PubMed and Web of Science were performed to identify and evaluate evidence for or against four propositions related to soyfoods and weight loss (Data from in vitro, animal, epidemiologic, and clinical studies were evaluated and summarized). (1) Certain soyfoods will improve weight and/or fat loss when fed at isolcaloric levels (similar calories given across experimental conditions, but not necessarily at a level to maintain current body weight); generally supportive evidence in animal studies, but there is no compelling support in human studies. (2) Certain soyfoods will improve weight and fat loss when included as part of a diet by affecting caloric intake; limited supportive evidence in animal and human studies. (3) Certain soyfoods will prevent/improve risk factors related to glucoregulatory function and cardiovascular health during weight loss; some evidence supporting this proposition, but additional evidence is needed before conclusions can be made. (4) Certain soyfoods will minimize the loss of bone mass during weight loss; no data available pertinent to this proposition. Limitations in existing data make it difficult to reach conclusions regarding these four propositions. Overall, the current data suggest that soyfoods are as good as other protein sources for promoting weight loss and there is a suggestive body of evidence that soyfoods may confer additional benefits, but results must be carefully interpreted and additional evidence is needed before making firm conclusions concerning soyfoods and weight loss.

Putative biases in estimating mortality attributable to obesity in the US population

BACKGROUND

A recent analysis concluded that there were fewer excess deaths attributable to obesity in the US population than previously believed. This analysis may not have fully corrected for two putative biases, the regression-dilution and the reverse-causation biases. It is not presently known whether correcting for these biases would increase estimates of excess deaths attributable to obesity.

METHODS

All-cause mortality hazard ratios (HRs) for different body mass index (BMI) categories were calculated and adjusted for confounding factors, using data from the prospective Atherosclerosis Risk in Communities Study. The analysis was based on 12 457 individuals aged 51-70 years and 606 all-cause deaths during a 5.3-year follow-up. The HRs were corrected for the regression-dilution and reverse-causation biases, and compared with data from a previously published study to evaluate the effects of correcting for these putative biases on estimates of excess deaths attributable to obesity in the US population.

RESULTS

The uncorrected all-cause mortality HR for obesity (BMI>/=30) was 1.26 (95% confidence interval (95% CI)=1.01-1.58), using the 21-25 kg/m(2) as ideal-weight category. Correcting for regression dilution increased the HR to 1.46 (95% CI=1.17-1.83). Correcting for both putative biases increased it further to 2.70 (95% CI=1.31-5.57). Such increases in HRs are consonant with increases of several hundred percent in estimates of deaths attributable to obesity in the US.

CONCLUSIONS

Correcting for putative biases yielded increases in all-cause mortality HRs for obesity that correspond to substantial increases in estimates of excess deaths attributable to obesity in the US population.

No effect of dietary fat on short-term weight gain in mice treated with atypical antipsychotic drugs

RATIONALE

Atypical antipsychotic drugs (AAD) induce significant weight gain in female C57BL/6J mice. The effect of dietary fat on weight gain and serum lipids in this model is unknown.

OBJECTIVES

Test the hypothesis that the obesigenic effects of these drugs are greater in the presence of a high-fat diet.

METHODS

Female C57BL/6J mice were treated with atypical antipsychotics for 3 weeks and fed either a low-fat or high-fat diet (4.6 vs 15.6% fat by wt). Food intake (FI), body weight (BW), body composition, and serum lipids were measured during treatment with optimized doses of olanzapine, quetiapine, and risperidone. Energy intake (EI) and feed efficiency (FE) were calculated. Group differences in change were analyzed via repeated measures analysis of variance (ANOVA). Serum lipid concentrations, EI and FE were compared using two-way ANOVA.

RESULTS

AAD-treated mice gained significantly more weight than controls after 3 weeks (P<0.001). Treatment and diet had significant effects on FI and EI over time (P<0.001). AAD-treated mice had significantly higher FE than controls (P<0.05); however, there was no significant drug by diet interaction (P=0.65). Risperidone low-fat mice gained significantly more absolute fat mass than placebo low-fat mice (P<0.05). All treatment groups, except quetiapine low-fat and olanzapine high-fat, gained significantly more absolute lean mass than placebo controls (P<0.05). Cholesterol levels were significantly lower in quetiapine and risperidone than placebo (P<0.05). Risperidone low-fat mice had significantly higher triglyceride levels than placebo and risperidone high-fat mice (P<0.05).

CONCLUSIONS

A high-fat diet does not increase AAD-induced BW gain in female mice during a 3-week treatment period.

Association of K121Q polymorphism in ENPP1 (PC-1) with BMI in Caucasian and African-American adults

OBJECTIVE

To test for association of the ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) K121Q polymorphism with body mass index (BMI) and diabetes in a large sample of Caucasians and African-Americans by selectively genotyping individuals at the extremes of the phenotypic distribution.

SUBJECTS

Subsets comprising the extremes of the BMI distribution (10th-20th and above the 90th BMI percentile for Caucasians and between the 10th-30th and above the 80th percentile for African-Americans) from a group of 10,260 Caucasian and 2268 African-American adults participating in New York Cancer Project were studied.

METHODS

Subjects were genotyped for the ENPP1 K121Q polymorphism by pyrosequencing and tested for association with BMI and diabetes by regression analysis.

RESULTS

Regression analysis with BMI as the dependent variable demonstrated a significant association (P = 0.02) of genotype at K121Q with BMI, with no significant race-by-genotype interaction (P = 0.30). Compared with Q/Q or Q/K individuals, the K/K individuals had a BMI approximately 1.3 kg/m2 higher, without effects of age, gender or race. By logistic regression analysis, the K121Q alleles had no significant effect on diabetes status (P = 0.37) in obese subjects.

CONCLUSION

In both Caucasians and African-Americans, the K121 polymorphism in ENPP1 was associated with increased BMI, but not with diabetes.

Racial differences in the prevalence of Factor V Leiden mutation among patients on chronic warfarin therapy

We report the prevalence of Factor V Leiden (FVL) in European American and African American patients on warfarin therapy residing in Alabama. METHODS.: Detailed history was obtained and FVL genotype was determined for 288 patients enrolled in a prospective cohort: Pharmacogenetic Optimization of Anticoagulation Therapy. Racial differences in genotype frequency were assessed by the Chi-square statistics and HWE assumptions by G-statistics. Race-specific analysis for the association between site of thromboembolism and the presence of FVL mutation was assessed using logistic regression. RESULTS.: The overall heterozygote (GA genotype) frequency was 4.9%. No patient was found to be homozygous (AA) for the variant allele. The prevalence of GA was higher in European American (8.6%) compared to African American (1.4%) patients (p=0.004). The FVL genotype frequency was significantly different across race for venous thromboembolic events (p=0.014) but not for arterial thromboembolic events (p=0.20). Multivariable race-specific analysis highlights the contribution of FVL mutation to the risk of venous thromboembolic events in European American (p=0.03) but not in African American patients (p=0.95). European American patients with the GA mutation were approximately 6.3 times more likely to have experienced a venous, rather than arterial thromboembolic event. CONCLUSION.: In Alabama, among patients on warfarin, the GA genotype is more prevalent in European Americans compared to African Americans. In European Americans, but not in African Americans, the GA genotype was more prevalent in patients with venous compared to arterial thromboembolic events.

Putative contributors to the secular increase in obesity: exploring the roads less traveled

OBJECTIVE

To investigate plausible contributors to the obesity epidemic beyond the two most commonly suggested factors, reduced physical activity and food marketing practices.

DESIGN

A narrative review of data and published materials that provide evidence of the role of additional putative factors in contributing to the increasing prevalence of obesity.

DATA

Information was drawn from ecological and epidemiological studies of humans, animal studies and studies addressing physiological mechanisms, when available.

RESULTS

For at least 10 putative additional explanations for the increased prevalence of obesity over the recent decades, we found supportive (although not conclusive) evidence that in many cases is as compelling as the evidence for more commonly discussed putative explanations.

CONCLUSION

Undue attention has been devoted to reduced physical activity and food marketing practices as postulated causes for increases in the prevalence of obesity, leading to neglect of other plausible mechanisms and well-intentioned, but potentially ill-founded proposals for reducing obesity rates.

Citrus aurantium and synephrine alkaloids in the treatment of overweight and obesity: an update

Obesity is a major health problem facing the developed and developing world. Efforts by individuals, health professionals, educators, and policy makers to combat the escalating trend of growing obesity prevalence have been multifaceted and mixed in outcome. Various dietary supplements have been marketed to reduce obesity. These products have been suggested to accomplish this by decreasing energy intake and energy absorption, and/or increasing metabolic rate. Ephedra, one such supplement, was banned from sale in the US market because of concerns about adverse events. Another substance, Citrus aurantium, which contains several compounds including synephrine alkaloids, has been suggested as a safe alternative. This review examines the evidence for safety and efficacy of C. aurantium and synephrine alkaloids as examined in animal studies, clinical weight loss trials, acute physiologic studies and case reports. Although at least three reviews of C. aurantium have been published, our review expands upon these by: (i) distinguishing and evaluating the efficacy of C. aurantium and related compounds; (ii) including results from previously unreviewed research; (iii) incorporating recent case reports that serve to highlight, in an anecdotal way, potential adverse events related to the use of C. aurantium and related compounds; and (iv) offering recommendations to guide the design of future trials to evaluate the safety and efficacy of C. aurantium. While some evidence is promising, we conclude that larger and more rigorous clinical trials are necessary to draw adequate conclusions regarding the safety and efficacy of C. aurantium and synephrine alkaloids for promoting weight loss.

Atomoxetine for weight reduction in obese women: a preliminary randomised controlled trial

BACKGROUND AND OBJECTIVE

Atomoxetine is a potent central norepinephrine uptake inhibitor, currently marketed for treatment of attention-deficit/hyperactivity disorder (ADHD). With the understanding that noradrenergic agents could be useful in assisting obese individuals to lose weight, we conducted this preliminary study to evaluate short-term efficacy and safety of atomoxetine in obese adults.

DESIGN

At 12-week randomised, double-blind, placebo-controlled trial, conducted at Duke University Medical Centre, USA, from May 2004 to December 2004.

PARTICIPANTS

A total of 30 obese women (mean (s.e.) body mass index of 36.1 (0.6) kg/m2).

INTERVENTIONS

Participants were randomly assigned to receive atomoxetine (n=15) or placebo (n=15). All participants were advised to follow a balanced hypocaloric diet (500 kcal/day deficit). Atomoxetine therapy was started at 25 mg/day orally, with gradual increase to 100 mg/day over 1 week. Placebo dosing was identical.

MEASUREMENTS

Body weight in kilograms was the primary outcome measure. Other measurements included waist circumference, blood pressure and heart rate, fasting plasma glucose and lipids, and depressive symptoms.

RESULTS

Last-observation-carried-forward analysis of the available data for participants who had completed at least one post-randomisation assessment, demonstrated that the atomoxetine group (n=12) lost more body weight over the 12-week period than the placebo (n=14) group (mean (s.e.) -3.6 (1.0) kg (-3.7% loss) vs 0.1 (0.4) kg (0.2% gain); F (4,96)=11.9; P<0.0001). Three participants in the atomoxetine group and none in the placebo group lost >or=5% weight. Side effects were minimal.

CONCLUSION

Atomoxetine demonstrated modest short-term weight loss efficacy relative to placebo in this preliminary study of obese women.

PYY3-36 as an anti-obesity drug target

The neuropeptide Y (NPY)/peptide YY (PYY) system has been implicated in the physiology of obesity for several decades. More recently ignited enormous interest in PYY3-36, an endogenous Y2-receptor agonist, as a promising anti-obesity compound. Despite this interest, there have been remarkably few subsequent reports reproducing or extending the initial findings, while at the same time studies finding no anti-obesity effects have surfaced. Out of 41 different rodent studies conducted (in 16 independent labs worldwide), 33 (83%) were unable to reproduce the reported effects and obtained no change or sometimes increased food intake, despite use of the same experimental conditions (i.e. adaptation protocols, routes of drug administration and doses, rodent strains, diets, drug vendors, light cycles, room temperatures). Among studies by authors in the original study, procedural caveats are reported under which positive effects may be obtained. Currently, data speak against a sustained decrease in food intake, body fat, or body weight gain following PYY3-36 administration and make the previously suggested role of the hypothalamic melanocortin system unlikely as is the existence of PYY deficiency in human obesity. We review the studies that are in the public domain which support or challenge PYY3-36 as a potential anti-obesity target.

Lack of association between polymorphism of the human cyclic GMP-dependent protein kinase gene and obesity

OBJECTIVE

To investigate whether genetic variation in the cyclic GMP-dependent protein kinase gene (PRKG1) is associated with obesity.

METHODS

The study included 143 individuals from New York City area, NY, USA. The subjects were sampled on the basis of body mass index (BMI): obese (BMI ranging from 33.8 to 89.5 kg/m(2)), and nonobese (BMI ranging from 16.0 to 29.4 kg/m(2)). The association between C2276T polymorphism in PRKG1 gene and obesity was tested using linear regression analysis.

RESULTS

BMI levels were predicted by linear regression models adjusted for demographic factors. An analysis was performed twice: in individuals of all ethnic backgrounds and in European-Americans only. In both cases, genotype did not have a significant effect.

CONCLUSION

We found no evidence that the C2276T polymorphism in the PKRG1 gene is associated with obesity.

Microarray profiling of isolated abdominal subcutaneous adipocytes from obese vs non-obese Pima Indians: increased expression of inflammation-related genes

AIMS/HYPOTHESIS

Obesity increases the risk of developing major diseases such as diabetes and cardiovascular disease. Adipose tissue, particularly adipocytes, may play a major role in the development of obesity and its comorbidities. The aim of this study was to characterise, in adipocytes from obese people, the most differentially expressed genes that might be relevant to the development of obesity.

METHODS

We carried out microarray gene profiling of isolated abdominal subcutaneous adipocytes from 20 non-obese (BMI 25+/-3 kg/m2) and 19 obese (BMI 55+/-8 kg/m2) non-diabetic Pima Indians using Affymetrix HG-U95 GeneChip arrays. After data analyses, we measured the transcript levels of selected genes based on their biological functions and chromosomal positions using quantitative real-time PCR.

RESULTS

The most differentially expressed genes in adipocytes of obese individuals consisted of 433 upregulated and 244 downregulated genes. Of these, 410 genes could be classified into 20 functional Gene Ontology categories. The analyses indicated that the inflammation/immune response category was over-represented, and that most inflammation-related genes were upregulated in adipocytes of obese subjects. Quantitative real-time PCR confirmed the transcriptional upregulation of representative inflammation-related genes (CCL2 and CCL3) encoding the chemokines monocyte chemoattractant protein-1 and macrophage inflammatory protein 1alpha. The differential expression levels of eight positional candidate genes, including inflammation-related THY1 and C1QTNF5, were also confirmed. These genes are located on chromosome 11q22-q24, a region with linkage to obesity in the Pima Indians.

CONCLUSIONS/INTERPRETATION

This study provides evidence supporting the active role of mature adipocytes in obesity-related inflammation. It also provides potential candidate genes for susceptibility to obesity.

Antipsychotic drug-induced weight gain: development of an animal model

OBJECTIVE

Weight gain is a prominent effect of most atypical antipsychotic drugs (AAPDs); yet, the mechanisms are not fully understood and no well-established mouse models exist for investigating the mechanisms. Thus, we developed a mouse model to evaluate the effects of AAPDs on eating, body weight (BW), and body composition.

METHODS

Female C57BL/6J mice were used to test olanzapine, quetiapine, ziprasidone, and risperidone. Mice were acclimated to individual housing, given ad libitum access to chow and water, dosed with placebo peanut butter pills for 1 week, and then dosed daily with AAPD-laced peanut butter pills for 4 weeks. Weekly food intakes and BWs were measured, and body compositions were determined at the end of each experiment.

RESULTS

After 4 weeks of treatment, olanzapine, quetiapine, ziprasidone, and risperidone caused significant weight increases, but only olanzapine and quetiapine were associated with significantly increased food intake. Body composition data revealed that olanzapine-treated mice had more relative fat mass and risperidone-treated mice had more relative lean mass than did control mice. Quetiapine and ziprasidone did not significantly affect relative body composition even though BW was increased.

CONCLUSIONS

Oral AAPD administration causes increased BW in female mice. Our mouse model of AAPD-induced weight gain resembles the human response to these medications and will be used to investigate the mechanisms for weight gain and fat accumulation.

Single-nucleotide polymorphisms in the C-reactive protein (CRP) gene promoter that affect transcription factor binding, alter transcriptional activity, and associate with differences in baseline serum CRP level

To investigate whether functional polymorphisms exist in the C-reactive protein (CRP) gene, i.e., ones that contribute directly to differences in baseline CRP among individuals, we sequenced a 1,156-nucleotide-long stretch of the CRP gene promoter in 287 ostensibly healthy people. We identified two single-nucleotide polymorphisms (SNPs), a bi-allelic one at nucleotide -409 (G-->A), and a tri-allelic one at -390 (C-->T-->A), both resident within the hexameric core of transcription factor binding E-box elements. Electrophoretic mobility shift assays confirmed that the SNP within the sequence (-412)CACGTG(-407) (E-box 1) modulates transcription factor binding, and that the one within (-394)CACTTG(-389) (E-box 2) supports transcription factor binding only when the -390 T allele is present. The commonest of four E-box 1/E-box 2 haplotypes (-409G/-390T) identified in the population supported highest promoter activity in luciferase reporter assays, and the rarest one (-409A/-390T) supported the least. Importantly, serum CRP in people with these haplotypes reproduced this rank order, i.e., people with the -409G/-390T haplotype had the highest baseline serum CRP (mean +/- SEM 10.9 +/- 2.25 microg/ml) and people with the -409A/-390T haplotype had the lowest (5.01 +/- 1.56 microg/ml). Furthermore, haplotype-associated differences in baseline CRP were not due to differences in age, sex, or race, and were still apparent in people with no history of smoking. At least two other SNPs in the CRP promoter lie within E-box elements (-198 C-->T, E-box 4, and -861 T-->C, E-box 3), indicating that not only is the quality of E-box sites in CRP a major determinant of baseline CRP level, but also that the number of E-boxes may be important. These data confirm that the CRP promoter does encode functional polymorphisms, which should be considered when baseline CRP is being used as an indicator of clinical outcome. Ultimately, development of genetic tests to screen for CRP expression variants could allow categorization of healthy people into groups at high versus low future risk of inflammatory disease.

Exactly which synephrine alkaloids does Citrus aurantium (bitter orange) contain?

Following the withdrawal of ephedrine from the dietary supplement marketplace sales of products containing Citrus aurantium (CA) (bitter orange) for weight loss are believed to have increased dramatically. CA contains a number of constituents speculated to lead to weight loss, of which the most frequently cited constituent is synephrine. Concerns have been raised about the safety of products containing synephrine. To develop an adequate basis for clinical and public health recommendations, it is necessary to understand the nature of the synephrine alkaloids in CA. There are six possible isomers of synephrine (para, meta, ortho; and for each a d or l form). Some authors have stated that CA contains only p-synephrine, whereas other authors have stated that CA contains m-synephrine. This is an important distinction because the two molecules have different pharmacologic properties, which may differentially affect safety and efficacy. We are unable to identify published data that explicitly show whether CA contains p-synephrine, m-synephrine, or both. In this brief report, we show that at least one product purportedly containing synephrine alkaloids from CA contains both p-synephrine and m-synephrine. We believe this justifies further investigation into which synephrine alkaloids are present in CA and products purportedly containing synephrine alkaloids from CA and the relative quantities of each of the different isomers.

Prevalence of obesity in the United States

Obesity is a major public health problem in the United States. Data on measured heights and weights indicates that the prevalence of obesity has significantly increased among the US population over the past 30 years. Data collected from 1999 to 2002 estimates that nearly 1/3 of adults are obese (27.6% of men and 33.2% of women) and one in six children and adolescents is overweight. Increased prevalence of excessive weight is noted among all age, gender and racial/ethnic groups; however, disparities exist. There is a need for further research to better understand why these increases have occurred, why the observed disparities exist and how to reverse these trends.