The Obesity Epidemic and Its Impact on Urologic Care

Although heart disease and cancer are the number one and two causes of death in the United States, respectively, obesity is gaining speed as a contributing cause to both of those conditions, along with diabetes, arthritis, dyslipidemia, coronary heart disease, gallbladder disease, and certain malignancies. Nearly one-third of the adults in the United States is overweight with a body mass index (BMI) greater than 25 kg/m², and another third of the adult population is obese, with a BMI greater than 30 kg/m². This article reviews the root causes of obesity, the societal implications, and the implications of obesity on various urologic diseases.Key words: Obesity, Morbid obesity, Body mass index, Exercise, Weight loss, Diet, EpidemicMore than 20% of adults in the United States are clinically obese, defined by a body mass index (BMI) of 30 kg/m² or higher, and an additional 30% are overweight, with a BMI between 25 and 30 kg/m².¹ An environment that promotes excessive food intake and discourages physical activity lies at the root of the current obesity epidemic. Although humans have excellent physiologic mechanisms to defend against body weight loss, they have only weak physiologic mechanisms to defend against body weight gain when food is abundant. So much has been discussed about the obesity epidemic that it’s easy to think the issue is being blown out of proportion. After all, people putting on a few pounds may not seem to warrant the proclamation of a national emergency. Although obesity may not attract the degree of attention that heart disease and cancer do, it is a serious public health issue. Experts agree that, as more and more obese children become obese adults, the diseases associated with obesity, such as heart disease, cancer, and particularly diabetes, will surge.The obesity epidemic in the United States is an unintended consequence of the economic, social, and technologic advances realized during the past several decades. The food supply is abundant and low in cost, and palatable foods with high caloric density are readily available in prepackaged forms and at fast-food restaurants. Laborsaving technologies have greatly reduced the amount of physical activity that used to be part of everyday life, and the widespread availability of electronic devices in the home, school, and office has promoted a sedentary lifestyle, particularly among children.A recent study estimated that medical expenditures attributed to overweight and obesity accounted for 9.1% of total US medical expenditures in 1998, and might have reached $78.5 billion dollars.² Today, the healthcare costs attributed to obesity are estimated to be $190 billion—nearly 21% of total US healthcare costs.³ Expenditures will continue to rise, particularly due to increases in the prevalence of obesity and the cost of related healthcare.Total healthcare costs attributable to this obesity epidemic are expected to double every decade, reaching $860.7 to $956.9 billion by 2030, accounting for 16% to 18% of total US healthcare costs, or 1 in every 6 dollars spent on healthcare. ⁴ In addition, obesity is likely to result in a decreased life expectancy for our population. Current US generations may have a shorter life expectancy than their parents if this obesity epidemic cannot be controlled.⁵ Based on nationally representative data and the assumptions of a future of increased obesity rates, along with increased healthcare costs, this paints an alarming picture of the future obesity epidemic. Projections show that if the trends continue, in 15 years, 80% of all American adults will be overweight or obese.⁶     

Metabolomic profiling reveals mitochondrial-derived lipid biomarkers that drive obesity-associated inflammation

Obesity has reached epidemic proportions worldwide. Several animal models of obesity exist, but studies are lacking that compare traditional lard-based high fat diets (HFD) to "Cafeteria diets" (CAF) consisting of nutrient poor human junk food. Our previous work demonstrated the rapid and severe obesogenic and inflammatory consequences of CAF compared to HFD including rapid weight gain, markers of Metabolic Syndrome, multi-tissue lipid accumulation, and dramatic inflammation. To identify potential mediators of CAF-induced obesity and Metabolic Syndrome, we used metabolomic analysis to profile serum, muscle, and white adipose from rats fed CAF, HFD, or standard control diets. Principle component analysis identified elevations in clusters of fatty acids and acylcarnitines. These increases in metabolites were associated with systemic mitochondrial dysfunction that paralleled weight gain, physiologic measures of Metabolic Syndrome, and tissue inflammation in CAF-fed rats. Spearman pairwise correlations between metabolites, physiologic, and histologic findings revealed strong correlations between elevated markers of inflammation in CAF-fed animals, measured as crown like structures in adipose, and specifically the pro-inflammatory saturated fatty acids and oxidation intermediates laurate and lauroyl carnitine. Treatment of bone marrow-derived macrophages with lauroyl carnitine polarized macrophages towards the M1 pro-inflammatory phenotype through downregulation of AMPK and secretion of pro-inflammatory cytokines. Results presented herein demonstrate that compared to a traditional HFD model, the CAF diet provides a robust model for diet-induced human obesity, which models Metabolic Syndrome-related mitochondrial dysfunction in serum, muscle, and adipose, along with pro-inflammatory metabolite alterations. These data also suggest that modifying the availability or metabolism of saturated fatty acids may limit the inflammation associated with obesity leading to Metabolic Syndrome.     

The politics of pathology: how obesity became an epidemic disease

Americans' recent weight gains have been widely described as an "obesity epidemic." Such a characterization, however, has many problems: the average American weight gain has been relatively low (eight to 12 pounds over the last 20 years), and the causal linkages between adiposity, morbidity, and mortality are unclear. Nevertheless, the media and numerous health officials continue to sound dire warnings that obesity has become an epidemic disease. In this article, I examine how and why America's growing weight became an "obesity epidemic." I find the disease characterization has less to do with the health consequences of excess weight and more with the various financial and political incentives of the weight loss industry, medical profession, and public health bureaucracy. This epidemic image was also assisted by the method of displaying information about weight gain with maps in PowerPoint slides. Such characterizations, I argue, are problematic. Given the inconclusive scientific evidence and the absence of a safe and effective weight loss regimen, calling America's growing weight an epidemic disease is likely to cause more harm than good.     

Redrawing the US Obesity Landscape: Bias-Corrected Estimates of State-Specific Adult Obesity Prevalence

Background

State-level estimates from the Centers for Disease Control and Prevention (CDC) underestimate the obesity epidemic because they use self-reported height and weight. We describe a novel bias-correction method and produce corrected state-level estimates of obesity and severe obesity.

Methods

Using non-parametric statistical matching, we adjusted self-reported data from the Behavioral Risk Factor Surveillance System (BRFSS) 2013 (n = 386,795) using measured data from the National Health and Nutrition Examination Survey (NHANES) (n = 16,924). We validated our national estimates against NHANES and estimated bias-corrected state-specific prevalence of obesity (BMI≥30) and severe obesity (BMI≥35). We compared these results with previous adjustment methods.

Results

Compared to NHANES, self-reported BRFSS data underestimated national prevalence of obesity by 16% (28.67% vs 34.01%), and severe obesity by 23% (11.03% vs 14.26%). Our method was not significantly different from NHANES for obesity or severe obesity, while previous methods underestimated both. Only four states had a corrected obesity prevalence below 30%, with four exceeding 40%–in contrast, most states were below 30% in CDC maps.

Conclusions

Twelve million adults with obesity (including 6.7 million with severe obesity) were misclassified by CDC state-level estimates. Previous bias-correction methods also resulted in underestimates. Accurate state-level estimates are necessary to plan for resources to address the obesity epidemic.     

Mechanisms of obesity-related hypertension.

Obesity has become an epidemic problem in western societies, contributing to metabolic diseases, hypertension and cardiovascular disease. Although the importance of obesity as a cause of hypertension is well established, the molecular basis of the relationship between obesity and increased blood pressure remains poorly understood. This brief review examines the association between obesity and hypertension along with the mechanisms proposed to explain this association, while presenting evidence of a direct causal effect of adipose tissue in the development of hypertension through the involvement of the adrenal cortex.     

Genome-wide analysis reveals DNA methylation markers that vary with both age and obesity

The combination of the obesity epidemic and an aging population presents growing challenges for the healthcare system. Obesity and aging are major risk factors for a diverse number of diseases and it is of importance to understand their interaction and the underlying molecular mechanisms. Herein the authors examined the methylation levels of 27578 CpG sites in 46 samples from adult peripheral blood. The effect of obesity and aging was ascertained with general linear models. More than one hundred probes were correlated to aging, nine of which belonged to the KEGG group map04080. Additionally, 10 CpG sites had diverse methylation profiles in obese and lean individuals, one of which was the telomerase catalytic subunit (TERT). In eight of ten cases the methylation change was reverted between obese and lean individuals. One region proved to be differentially methylated with obesity (LINC00304) independent of age. This study provides evidence that obesity influences age driven epigenetic changes, which provides a molecular link between aging and obesity. This link and the identified markers may prove to be valuable biomarkers for the understanding of the molecular basis of aging, obesity and associated diseases.     

Developmental origin of fat: tracking obesity to its source

The development of obesity not only depends on the balance between food intake and caloric utilization but also on the balance between white adipose tissue, which is the primary site of energy storage, and brown adipose tissue, which is specialized for energy expenditure. In addition, some sites of white fat storage in the body are more closely linked than others to the metabolic complications of obesity, such as diabetes. In this Review, we consider how the developmental origins of fat contribute to its physiological, cellular, and molecular heterogeneity and explore how these factors may play a role in the growing epidemic of obesity.     

Lasker lauds leptin

This year, the Albert Lasker Basic Medical Research Award will be shared by Douglas Coleman and Jeffrey Friedman for their discovery of leptin, a hormone that regulates appetite and body weight. By uncovering a critical physiologic system, their discovery markedly accelerated our capacity to apply molecular and genetic techniques to understand obesity.     

Lasker lauds leptin

This year, the Albert Lasker Basic Medical Research Award will be shared by Douglas Coleman and Jeffrey Friedman for their discovery of leptin, a hormone that regulates appetite and body weight. By uncovering a critical physiologic system, their discovery markedly accelerated our capacity to apply molecular and genetic techniques to understand obesity.     

Targeting Autophagy in Obesity‐Associated Heart Disease

Over the past three decades, the increasing rates of obesity have led to an alarming obesity epidemic worldwide. Obesity is associated with an increased risk of cardiovascular diseases; thus, it is essential to define the molecular mechanisms by which obesity affects heart function. Individuals with obesity and overweight have shown changes in cardiac structure and function, leading to cardiomyopathy, hypertrophy, atrial fibrillation, and arrhythmia. Autophagy is a highly conserved recycling mechanism that delivers proteins and damaged organelles to lysosomes for degradation. In the hearts of patients and mouse models with obesity, this process is impaired. Furthermore, it has been shown that autophagy flux restoration in obesity models improves cardiac function. Therefore, autophagy may play an important role in mitigating the adverse effects of obesity on the heart. Throughout this review, we will discuss the benefits of autophagy on the heart in obesity and how regulating autophagy might be a therapeutic tool to reduce the risk of obesity‐associated cardiovascular diseases.     

Evolutionary conservation of metabolism explains howDrosophila nutrigenomics can help us understand human nutrigenomics

While large populations in the third world are enduring famine, much of the developed world is undergoing an obesity epidemic. In addition to reflecting an unbalanced distribution of food, the "epidemic of overabundance" is ironically leading to a decrease in the health and longevity of the obese and improperly nourished in the first world. International consortia, such as the European Nutrigenomics Organization (NuGO), are increasing our knowledge of nutrientgene interactions and the effects of diet and obesity on human health. In this review, we summarize both previous and ongoing nutrigenomics studies in Drosophila and we explain how these studies can be used to provide insights into molecular mechanisms underlying nutrigenomics in humans. We will discuss how quantitative trait locus (QTL) experiments have identified genes that affect triglyceride levels in Drosophila, and how microarray analyses show that hundreds of genes have altered gene expression under different dietary conditions. Finally, we will discuss ongoing combined microarray-QTL studies, termed "genetical genomics," that promise to identify "master modulatory loci" that regulate global responses of potentially hundreds of genes under different dietary conditions. When "master modulatory loci" are identified in Drosophila, then experiments in mammalian models can be used to determine the relevance of these genes to human nutrition and health.     

Diabetes, the ice free corridor, and the Paleoindian settlement of North America

Since the 1940s, many Amerindian populations, including some with mixed Amerindian ancestry, have experienced an epidemic of obesity and adult-onset diabetes (NIDDM). Obesity and NIDDM were apparently rare among Amerindian populations prior to that time. Though the evidence is equivocal, obesity and NIDDM seem to be rare today among Athapaskan Amerindians of the North American Arctic, sub-Arctic, and Southwest. It is hypothesized that the Amerindian genotype(s) susceptible to obesity and NIDDM arose from selection favoring "thrifty" genes during the peopling of North America south of the continental glaciers. "Thrifty" genes (Neel: Am. J. Hum. Genet. 14:353-362, 1962) allowed a more efficient food metabolism as hunter-gatherers from an unusually harsh mid-latitude tundra environment (the "ice free" corridor) adapted to more typical mid-latitude environments to the south. The early Paleoindian settlement pattern from Wyoming to Arizona and Texas indicates a relatively brief period of reliance on unpredictable big game resources in lower elevations and smaller game and gathered resources in higher elevations. This unusual "specialist" settlement pattern may have resulted from the early Paleoindian's unfamiliarity with gathered foods and small game in lower elevations. Athapaskan populations evidently moved south from Beringia sometime after the Paleoindian migration when the "ice free" corridor had widened and contained environments and resources more typical of subarctic latitudes. Thus, Athapaskan hunter-gatherers could gradually adapt to the resources of lower latitudes such that "thrifty" genes would not have been as advantageous. The interaction of recently introduced "western" diets and "thrifty" genes have evidently led to today's epidemic of obesity and NIDDM among Amerindians of Paleoindian ancestry.     

Thinking Evolutionarily About Obesity

Obesity, diabetes, and metabolic syndrome are growing worldwide health concerns, yet their causes are not fully understood. Research into the etiology of the obesity epidemic is highly influenced by our understanding of the evolutionary roots of metabolic control. For half a century, the thrifty gene hypothesis, which argues that obesity is an evolutionary adaptation for surviving periods of famine, has dominated the thinking on this topic. Obesity researchers are often not aware that there is, in fact, limited evidence to support the thrifty gene hypothesis and that alternative hypotheses have been suggested. This review presents evidence for and against the thrifty gene hypothesis and introduces readers to additional hypotheses for the evolutionary origins of the obesity epidemic. Because these alternate hypotheses imply significantly different strategies for research and clinical management of obesity, their consideration is critical to halting the spread of this epidemic.     

Behavioral, environmental, metabolic and intergenerational components of early life undernutrition leading to later obesity in developing nations and in minority groups in the U.S.A

Nutritional transition, urbanization, and physical inactivity are primary factors responsible for the worldwide epidemic of overweight/obesity (OW/OB). However, these factors fail to explain the epidemic of OW/OB in developing countries and in recent-migrants to developed countries. Among these, OW/OB is associated with short/stunted stature and coexists with undernutrition at much higher rates than is statistically expected. Changes in metabolic pathways toward reduced fat oxidation and increased metabolism of carbohydrate may explain, in part, this phenomenon. Also, intergenerational consequences of malnutrition and poor health of the mothers may lead to impaired phenotypes in their offspring. We propose a novel methodology to assess the history of early life malnutrition by assessing the sitting height ratio of the mothers. The degree of "short leggedness" reflects undernutrition when the mother was an infant/child. Collectively, behavioral, environmental, metabolic and intergenerational components of early life undernutrition may provide a more satisfactory explanation for later life obesity.     

Obesity reduction within a generation: the dual roles of prevention and treatment

In 2010, the White House Task Force on Childhood Obesity provided benchmark goals for reducing childhood obesity. We evaluated the balance of prevention and treatment required for achieving Task Force goals in benchmark years 2015, 2020, and 2030. We created a simulation of US birth cohorts (2-19 years) born 2008-2030. For each year, we assumed "old" birth cohorts (part of previous benchmark obesity estimates) would benefit from obesity treatment strategies, and "new" birth cohorts would benefit from obesity prevention strategies. We assessed obesity prevalence that must be achieved through prevention strategies, under varying assumptions of treatment effectiveness. When we assumed a 1% absolute reduction in prevalence through treatment, we found that prevention strategies would need to achieve an obesity prevalence of 12% by 2015, 8% by 2020, and 0.3% by 2030. Because of higher obesity prevalence among minority children, prevention strategies would need to achieve a negative prevalence by 2030, which is implausible. Under more generous assumptions of treatment effectiveness, estimates became positive but remained low. Task Force goals are more difficult to achieve with each benchmark year. Policies must focus on obesity treatment interventions, particularly targeted to racial/ethnic minority children, to make progress in stemming the epidemic.     

Epidemic inflammation: pondering obesity

Over the past two decades, inflammation has been recognized as a major driver in the pathogenesis of several common diseases, including atherosclerosis, diabetes, cancer, and asthma. Over the same period, there has been a steep rise in the incidence of obesity, a major risk factor for these disorders. Inflammation of adipose tissue is now recognized to accompany obesity and contribute to its sequelae. Thus, whereas obesity is primarily a disorder of energy balance, it may be helpful to consider it also as a form of epidemic inflammation that predisposes to other forms of epidemic inflammation. It is a fundamental biologic challenge to understand how a positive energy balance and inflammation are linked. This work reviews evidence that reactive oxygen and nitrogen intermediates (ROI and RNI) help drive chronic inflammation in the obese. This is proposed to be a maladaptive instance of our evolved dependence on ROI and RNI for both homeostatic signaling and host defense. ROI and RNI are well suited for these seemingly contradictory dual functions by their metabolic origin, high diffusibility in water and lipid, atomic specificity, and large number of molecular targets. When we eat so much and work so little that we repeatedly generate reactive compounds at levels normally reserved for emergencies, we treat our own cells like invading microbes.     

Stress mechanisms and metabolic complications.

Stress can be defined as a state of threatened homeostasis or disharmony. An intricate repertoire of physiologic and behavioral responses is mobilized under stressful situations forming the adaptive stress response that aims to reestablish the challenged body equilibrium. The hypothalamic-pituitary-adrenal axis and the central and peripheral components of the autonomic nervous system constitute the two main pillars that subserve the vital functions of the stress system. Chronic stress represents a prolonged threat to homeostasis that can progressively lead to a deleterious overload with various complications caused by both the persistent stressor and the detrimental prolongation of the adaptive response. Recent data indicate that chronic stress is associated to derangement of metabolic homeostasis that contributes to the clinical presentation of visceral obesity, type 2 diabetes, atherosclerosis and metabolic syndrome. Notably, indices of stress in the modern western societies correlate with the increasing incidence of both obesity and the metabolic syndrome which have reached epidemic proportions over the past decades. The pathogenetic mechanisms that accommodate these correlations implicate primarily the chronic hyperactivation of the HPA axis under prolonged stress, which favors accumulation of visceral fat, and VICE VERSA; obesity constitutes a chronic stressful state that may cause HPA axis dysfunction. In addition, obesity is being now recognized as a systemic low grade inflammatory state that contributes to the derangement of the metabolic equilibrium, implicating the adipocyte secretion of adipokines to the pathogenesis of several components of the metabolic syndrome. Understanding the mechanisms that mediate the documented reciprocal relationships between stress and metabolic homeostasis will hopefully provide novel insights to the pathophysiology of obesity, type 2 diabetes, and their cardiometabolic complications, and will help the quest for more specific and effective therapeutic interventions.     

Contributions of Incidence and Persistence to the Prevalence of Childhood Obesity during the Emerging Epidemic in Denmark

Background

Prevalence of obesity is the result of preceding incidence of newly developed obesity and persistence of obesity. We investigated whether increasing incidence and/or persistence during childhood drove the prevalence of childhood obesity during the emerging epidemic.

Methods

Height and weight were measured at ages 7 and 13 years in 192,992 Danish school children born 1930–1969. Trends in the incidence (proportion obese at 13 years among those not obese at 7 years) and persistence (proportion obese at 13 years among those obese at 7 years) across birth cohort periods (1930–41 with low stable prevalence of obesity, 1942–51 with increasing prevalence, 1952–69 with the higher, but stable prevalence) were investigated. Logistic regression was used to examine the associations between BMI at 7 years as a continuous trait, allowing interactions with the birth cohorts, and occurrence of obesity at 13 years.

Results

The prevalence of obesity was similar at 7 and 13 years and increased across birth cohorts in boys from around 0.1% to 0.5% and in girls from around 0.3% to 0.7%. The incidence of obesity between ages 7 and 13 years increased from 0.15% to 0.35% in boys and from 0.20% to 0.44% in girls. The persistence increased from 28.6% to 41.4% in boys and from 16.4% to 31.0% in girls. Despite a decrease over time, the remission of obesity occurred in >60% of obese children in the last birth cohort. However, the odds ratios of obesity at age 13 years in relation to the full range of BMI at 7 years remained unchanged across the birth cohort periods.

Conclusions/Significance

The development of the obesity epidemic in children was due to an increase in both incidence and persistence of obesity. Contrary to prevailing expectations, a large, although declining, proportion of children obese at an early age underwent remission during childhood.     

Impaired striatal Akt signaling disrupts dopamine homeostasis and increases feeding

Background

The prevalence of obesity has increased dramatically worldwide. The obesity epidemic begs for novel concepts and therapeutic targets that cohesively address “food-abuse” disorders. We demonstrate a molecular link between impairment of a central kinase (Akt) involved in insulin signaling induced by exposure to a high-fat (HF) diet and dysregulation of higher order circuitry involved in feeding. Dopamine (DA) rich brain structures, such as striatum, provide motivation stimuli for feeding. In these central circuitries, DA dysfunction is posited to contribute to obesity pathogenesis. We identified a mechanistic link between metabolic dysregulation and the maladaptive behaviors that potentiate weight gain. Insulin, a hormone in the periphery, also acts centrally to regulate both homeostatic and reward-based HF feeding. It regulates DA homeostasis, in part, by controlling a key element in DA clearance, the DA transporter (DAT). Upon HF feeding, nigro-striatal neurons rapidly develop insulin signaling deficiencies, causing increased HF calorie intake.

Methodology/Principal Findings

We show that consumption of fat-rich food impairs striatal activation of the insulin-activated signaling kinase, Akt. HF-induced Akt impairment, in turn, reduces DAT cell surface expression and function, thereby decreasing DA homeostasis and amphetamine (AMPH)-induced DA efflux. In addition, HF-mediated dysregulation of Akt signaling impairs DA-related behaviors such as (AMPH)-induced locomotion and increased caloric intake. We restored nigro-striatal Akt phosphorylation using recombinant viral vector expression technology. We observed a rescue of DAT expression in HF fed rats, which was associated with a return of locomotor responses to AMPH and normalization of HF diet-induced hyperphagia.

Conclusions/Significance

Acquired disruption of brain insulin action may confer risk for and/or underlie “food-abuse” disorders and the recalcitrance of obesity. This molecular model, thus, explains how even short-term exposure to “the fast food lifestyle” creates a cycle of disordered eating that cements pathological changes in DA signaling leading to weight gain and obesity.     

Imaging obesity: fMRI, food reward, and feeding

Animal studies have revealed brain regions that control homeostatic feeding, but the rampant overeating contributing to the obesity epidemic suggests the participation of "nonhomeostatic" control centers. Recent papers by Batterham et al. (2007) and Farooqi et al. (2007) link peptide YY(3-36) and leptin to the activation of nonhomeostatic brain regions.