Obesity in North America. An overview

Factors associated with improved short term survival in obese end stage renal disease patients

PURPOSE

In contrast to its role in the general population, obesity, defined as body mass index (BMI) > or = 30 kg/m(2), has been associated with improved survival in patients with end stage renal disease (ESRD). This apparent benefit has not been explained.

METHODS

Using the United States Renal Data System (USRDS), we performed an historical cohort study on 151,027 patients initiated on ESRD therapy between January 1, 1995 and June 30, 1997, who never received renal transplants, and who had information sufficient to calculate BMI. We explored the association of various comorbidities present at the time of dialysis initiation (from HCFA Form 2728) with the presence of obesity by logistic regression, and the association of obesity with patient survival, including specific causes of death, by Cox regression adjusting for factors known to be associated with survival in this population.

RESULTS

Obese patients had an unadjusted two-year survival of 68% compared with 58% for non obese patients. Obesity was independently associated with a reduced risk of mortality among chronic dialysis patients (adjusted hazard ratio (AHR) 0.75, 95% confidence interval, 0.72-0.78), after controlling for all comorbidities and risk factors. However, there were significantly adverse interactions among whites (AHR 1.22, 1.14-1.30, across all causes of death) and females (AHR 1.12, 1.04-1.20, entirely due to an increased risk of infectious death).

CONCLUSIONS

Obesity in patients presenting with ESRD is associated independently with reduced all cause mortality; however, the relationship is complex and is stronger in African Americans. In addition, subgroup analysis suggests that obesity is associated with increased risk of infectious death in females.

Weight loss causes increased mortality: cons

Short-term studies indicate that intentional weight loss (IWL) among obese persons significantly improves health variables that are often precursors or markers of chronic diseases (e.g. heart diseases, type-2 diabetes). Hence, it is logical to assume that IWL among obese persons would lead to increased longevity. On the whole, epidemiological studies, including recent ones that use conservative analytic approaches such as distinguishing between apparently IWL and unintentional weight loss (UWL), adjusting for potential confounders and excluding apparently unhealthy subjects, indicate that apparently IWL appears to neither increase nor decrease mortality rate. However, it is important to note that none of the existing studies were designed specifically to test the hypothesis that IWL reduces mortality rate, and given methodological problems, these studies do not provide a satisfactory way to address the body mass index (BMI)-mortality question. Several controlled clinical trials suggest that IWL may reduce mortality rate. However, even in these studies, it is important to acknowledge that subjects are randomized to conditions that produce more or less weight loss and not to distinct levels of weight loss per se. Nevertheless, while we await additional data from better designed studies, given our incomplete knowledge, we conclude that it seems more likely than not that IWL achieved by medically recommended methods does not increase and probably decreases mortality rate.

Cost of in-patient care over 7 years among surgically and conventionally treated obese patients

OBJECTIVE

Bariatric surgery improves cardiovascular risk factors and quality of life, but few studies have directly addressed the relation between obesity treatment and hospitalization costs. This prospective controlled study compares in-patient care between surgically and conventionally treated obese patients.

RESEARCH METHODS AND PROCEDURES

A total of 962 surgically and conventionally treated obese patients from the intervention study, Swedish Obese Subjects, were followed for 6 years. Changes in days of hospitalization and hospitalization costs were analyzed. Information on hospitalizations for each subject were obtained from the Swedish Hospital Discharge Register.

RESULTS

After 6 years, weight change was -16.7% in the surgical group and +0.9% in the control group (p < 0.0001). The cumulated hospital stay over 6 years was 23.4 days in the surgical group and 6.9 days in the control group (p < 0.0001). The average hospital cost for the surgical intervention was US$4300. Incremental costs that could be attributable to obesity surgery averaged US$1200 per year. After exclusion of hospitalizations for the surgical intervention and conditions common after bariatric surgery, there were no significant differences between the groups in number of hospital days or hospitalization costs.

DISCUSSION

Our experience from bariatric surgery indicates that average weight reductions of 16% will not reduce hospitalization costs over 6 years. Costs of bariatric surgery are limited and seem to be motivated given the marked improvements of cardiovascular risk factors, cardiac structure, and function and health-related quality of life.

Managing obesity: a survey of attitudes and practices among Israeli primary care physicians

OBJECTIVES

To document and assess Israeli family physicians' (FPs) knowledge, attitudes and practices regarding the management of overweight and obesity.

METHODS

Anonymous questionnaires were completed by 510 family physicians (82% compliance rate). The questionnaires were distributed in various continuous medical education sites of FPs in Israel. The measures included attitudes to and resources of knowledge on weight management, views regarding the prescription of drugs, approaches to and strategies recommended for weight loss.

RESULTS

In all, 73% of FPs viewed weight management as important and reported that they often treated cases of overweight and obesity, including for patients without concomitant risk factors. The medical advice most frequently offered is: increase physical activity, decrease number of total calories (eat less) and consultation with a dietitian (95, 81 and 58% respectively). However, most responders (72%) believed that they had limited efficacy in treating obesity and considered themselves not well prepared by medical school to treat overweight patients. Some 60% reported feeling that they have insufficient knowledge regarding nutritional issues. Regarding pharmacotherapy for treating obesity, only 66% knew the drugs' prescription indications. However, the vast majority (87%) knew about the gradual increase of weight after stopping drug treatment.

CONCLUSIONS

Knowledge gaps and ambivalent attitudes toward obesity management were found. More education focusing on obesity, from medical school to post-graduate learning, seems warranted based on these findings.

Craniofacial morphology in obese adolescents

Overweight and obesity are growing problems in the world today. A recent survey shows that about 30% of the adolescent and adult Swedish population is overweight or obese. The etiology is a combination of many factors, the most important of which are physical inactivity and high caloric diet. Obese children have a normal to accelerated growth rate despite low growth hormone (GH) levels. The aim of our study was to investigate whether craniofacial morphology differs between obese adolescents and normal weight adolescents. Lateral cephalograms from 39 adolescents with obesity, aged 14-16 years, were analysed and compared with lateral cephalograms from an equal number of sex- and aged-matched controls. Compared to the controls, the subjects in the obesity group showed increased mandibular length, prognathic jaws and a reduced upper anterior face height. Despite low GH levels, obese children have normal levels of insulin-like growth factor (IGF-1). Since we found an advanced craniofacial growth in obese adolescents with low GH and high IGF-1 serum levels, craniofacial growth may be more dependent on free circulating LGF-1 than on the locally produced portion.

A genomewide linkage scan for quantitative-trait loci for obesity phenotypes

Obesity is an increasingly serious health problem in the world. Body mass index (BMI), percentage fat mass, and body fat mass are important indices of obesity. For a sample of pedigrees that contains >10,000 relative pairs (including 1,249 sib pairs) that are useful for linkage analyses, we performed a whole-genome linkage scan, using 380 microsatellite markers to identify genomic regions that may contain quantitative-trait loci (QTLs) for obesity. Each pedigree was ascertained through a proband who has extremely low bone mass, which translates into a low BMI. A major QTL for BMI was identified on 2q14 near the marker D2S347 with a LOD score of 4.04 in two-point analysis and a maximum LOD score (MLS) of 4.44 in multipoint analysis. The genomic region near 2q14 also achieved an MLS >2.0 for percentage of fat mass and body fat mass. For the putative QTL on 2q14, as much as 28.2% of BMI variation (after adjustment for age and sex) may be attributable to this locus. In addition, several other genomic regions that may contain obesity-related QTLs are suggested. For example, 1p36 near the marker D1S468 may contain a QTL for BMI variation, with a LOD score of 2.75 in two-point analysis and an MLS of 2.09 in multipoint analysis. The genomic regions identified in this and earlier reports are compared for further exploration in extension studies that use larger samples and/or denser markers for confirmation and fine-mapping studies, to eventually identify major functional genes involved in obesity.

Differential associations of body mass index and adiposity with all-cause mortality among men in the first and second National Health and Nutrition Examination Surveys (NHANES I and NHANES II) follow-up studies

OBJECTIVE

The frequently observed U-shaped relationship between body mass index (BMI; kg/m(2)) and mortality rate may be due to the opposing effects of fat mass (FM) and fat-free mass (FFM) components of BMI on mortality rate. The purpose is to test the hypothesis stated above.

DESIGN

Longitudinal prospective cohort studies. The mortality follow-up of the first and second National Health and Nutrition Examination Surveys (NHANES I and NHANES II).

SUBJECTS

A total of 10 169 male subjects aged 25-75 who participated in NHANES I and II were selected for analyses. Follow-up continued until 1992. The mean follow-up time was 14.6 y for NHANES I and 12.9 y for NHANES II. Ninety-eight percent of the participants were successfully followed representing a total of 3722 deaths.

MEASUREMENTS

Subscapular and triceps skinfolds thickness were used as FM indicators, whereas upper arm circumference was used as a FFM indicator. The Cox proportional hazards model tested the relationships of BMI, FM and FFM with all-cause mortality adjusting for age, smoking status, race and education levels.

RESULTS

BMI had a U-shaped relationship with mortality, with a nadir of approximately 27 kg/m(2). However, when indicators of FM and FFM were added to the model, the relationship between BMI and mortality became more nearly monotonic increasing. Moreover, the relationship between FM indicator and mortality was monotonic increasing and the relationship between FFM indicator and mortality was monotonic decreasing.

CONCLUSION

These results support the hypothesis that the apparently deleterious effects of marked thinness may be due to low FFM and that, over the observed range of the data, marked leanness (as opposed to thinness) has beneficial effects.

Venous thrombosis incidence in burn patients: preliminary results of a prospective study

There are few prospective data on the incidence of deep venous thrombosis (DVT) in burn patients. In an on-going prospective study, hospitalized burn patients 18 years or older with an expected hospital length of stay more than 72 hours were imaged with baseline venous duplex ultrasound of all extremities within the first 48 hours after admission and weekly until discharge. Patient demographics and clinical risk factors for DVT were assessed. At the time of submission, 40 patients met screening criteria, and 30 were enrolled. Ultrasound diagnosed seven patients with 11 acute DVT for an incidence of 23%. One pulmonary embolism was documented. DVT patients had a mean age of 49 +/- 23 years with an average TBSA burn of 15 +/- 4% compared with those without thrombosis with a mean age of 44 +/- 17 years (P = NS) and TBSA burn of 18 +/- 25% (P = NS). There were no statistically significant differences for DVT patients in terms of age, number of central line days, hospital length of stay, or TBSA burned. Given the preliminary findings of this small study, we believe that all hospitalized burn patients are at risk for DVT. On-going investigation will be helpful in defining level of risk and improved prevention strategies for thromboembolic complications in burn patients.

Human obesity: an evolutionary approach to understanding our bulging waistline

The unique worldwide spread of the human species and the remarkably long post-reproductive survival show that our genome permits excellent adaptation to vastly different environments. Moreover, the main scourges of later age, namely malignant growths and atherosclerosis, appear in humans later than in shorter-living animals. In recent years, excess weight and obesity have become mass phenomena with a pronounced upward trend in all developed countries. However, despite the detrimental effects of being overweight, these populations live longer than ever, which in part may be explained by the availability of better medical treatment. The prevalence and predicted further spread of obesity can be understood in the light of evolution. In all animal species energy metabolism is asymmetric with energy accumulation ('thrifty genotype') being the necessary condition of survival during hard times. For humans, which are no different to other animals in this respect, this genetic programming was necessary for survival because during the course of history, including the recorded history in the more developed Middle East, Europe or China, there was never a long period of uninterrupted food abundance, whereas famines were regular and frequent. Therefore fat accumulation, when food was available, meant survival at times of shortage, while the possible detrimental effects of overindulgence in food and being overweight expressed in unrealistically old age were irrelevant. It is the central, mostly intra-abdominal fat (in both humans and animals) that is more medically important than the subcutaneous truncal fat, and the accumulation of both types of fat is conditioned by high food consumption; therefore it is a historic novelty for human populations. In contrast, lower-body fat in human females is unique in the animal kingdom: it is much less metabolically active, it is of much lower pathologic significance than central fat, and it is programmed to be mobilized mostly during pregnancy and lactation. In view of all this, norms of desired weight should be based on hard mortality and morbidity statistics and not on theoretical, esthetic or fashion considerations. By this criterion, the upper limit of desirable weight is likely to be body mass index (BMI) 27 or 28, but specified for different populations (sex, race, ethnic origin); moreover, with aging, the detrimental effects of obesity diminish and finally disappear. Risks of other pathologies related to obesity (e.g. diabetes, hypertension and coronary disease) are also population-specific. However, total fatness, measured by BMI, is insufficiently sensitive as a risk factor, and fat distribution (upper-body versus low-body type, as reflected by waist circumference and waist:hip ratio) plays at least as prominent a role. Therefore the detailed norms, not yet available, should take into account both general obesity and fat distribution and be specific for different populations. Since long-term weight loss in adults is rarely achievable, public health measures should be aggressively directed at the prevention of obesity from childhood.

Obesity and health-related quality of life

Although it is well documented that obesity is strongly associated with morbidity and mortality, less is known about the impact of obesity on functional status and health-related quality of life (HRQL). However, in recent years research has been conducted to estimate the impact of obesity on HRQL, and to determine the effects of weight reduction on HRQL. The majority of published studies indicate that obesity impairs HRQL, and that higher degrees of obesity are associated with greater impairment. Obesity-associated decrements on HRQL tend to be most pronounced on physical domains of functioning. Studies of the effect of obesity surgery among morbidly obese patients indicate that this procedure produces significant and sustained improvements in the majority of HRQL indices; among mild-to-moderately obese persons, modest weight reduction derived from lifestyle modification also appears to improve HRQL, at least in the short term. Additional research is needed to (1) further characterize the effect that obesity has on HRQL; (2) estimate the short- and long-term effects of various methods of weight reduction (e.g. surgery, lifestyle modification) on HRQL; (3) improve both the conceptualization and measurement of HRQL to incorporate the personal preferences and values of the patient; and (4) develop ways to enhance and sustain positive changes in HRQL, even if weight maintenance is elusive.

The genetic epidemiology of thinness

Most genetic research in the area of human obesity asks the question 'Why are certain people obese?' Considerably less attention has been paid to the question of why certain people are not obese, particularly given the obesogenic environment that permeates the western culture. We present data from human and animal studies and evolutionary arguments supporting the notion that genetic studies of thinness or obesity resistance may yield important and complementary findings to genetic studies of obesity. We offer strategies for further refining the definition of thinness, weigh the advantages and disadvantages of potential sampling strategies and suggest candidate genes for thinness or obesity resistance.

An update on the science and therapy of obesity and its relationship to osteoarthritis

Obesity and osteoarthritis are two commonly encountered clinical problems that can lead to significant physical and emotional disability. This report examines the association between obesity and osteoarthritis, and discusses potential mechanisms by which obesity influences osteoarthritis. Special attention is devoted to reviewing the molecular and genetic mechanisms that underlie the development of clinical obesity. Improved understanding of obesity will hopefully lead to improved treatment and subsequent amelioration of this important risk factor for osteoarthritis.

Characterization of genetic and lifestyle factors for determining variation in body mass index, fat mass, percentage of fat mass, and lean mass

In this study, we simultaneously characterized genetic and lifestyle factors (exercise, smoking, and alcohol consumption) in determining variation in body mass index (BMI), fat mass, percentage of fat mass (PFM), and lean mass while adjusting for the effects of age and sex. Six hundred fifty-eight Caucasian individuals from 48 pedigrees were studied for BMI. Among these individuals, 289 from 38 pedigrees were studied for fat mass, PFM, and lean mass measured by dual X-ray absorptiometry (DXA). After adjusting for age, sex, and lifestyle factors, the heritabilities (h(2)) of BMI, fat mass, PFM, and lean mass ranged from 0.52 to 0.57 with associated standard errors ranging from 0.09 to 0.14. After accounting for significant sex and age effects, exercise had significant effects for all the phenotypes studied, and the effects of smoking and alcohol consumption were not significant. Therefore, significant proportions of variation in BMI, fat mass, PFM, and lean mass were under genetic control, and exercise had a significant effect in reducing BMI, fat mass, and PFM and in increasing lean mass. This study warrants further genetic linkage analyses to search for genes for the obesity-related phenotypes measured by DXA in our population.

Public health interventions for the prevention and treatment of obesity

Epidemic obesity is one of the few undesirable consequences of humanity's mastery of the environment. This article reviews public health approaches to preventing and treating obesity. The most encouraging efforts to date have been interventions targeting children in both medical and community surroundings. Treating and preventing obesity in adults has been less successful. It is suggested that taking an environmental health perspective on the obesity problem may facilitate the advancement of scientific understanding of this important health issue.