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Try out PMC Labs and tell us what you think. Learn More. The epidemic of overweight and obesity presents a major challenge to chronic disease prevention and health across the life course around the world. Fueled by economic growth, industrialization, mechanized transport, urbanization, an increasingly sedentary lifestyle, and a nutritional transition to processed foods and high calorie diets over the last 30 years, many countries have witnessed the prevalence of obesity in its citizens double, and even quadruple.
Rising prevalence of childhood obesity, in particular, forebodes a staggering burden of disease in Dominant women photos and healthcare systems in the decades to come. A complex, multifactorial disease, with genetic, behavioral, socioeconomic, and environmental origins, obesity raises risk of debilitating morbidity and mortality. Relying primarily on epidemiologic evidence published within the last decade, this non-exhaustive review discusses the extent of the obesity epidemic, its risk factors—known and novel—, sequelae, and economic impact across the globe.
While growth trends in overall obesity in most developed countries seem to have leveled off 2morbid obesity in many of these countries continues to climb, including among children. In addition, obesity prevalence in developing countries continues to Dominant women photos upwards toward US levels. Obesity is typically defined quite simply as excess body weight for height, but this simple definition belies an etiologically complex phenotype primarily associated with excess adiposity, Dominant women photos body fatness, that can manifest metabolically and not just in terms of body size 6.
Obesity greatly increases risk of chronic disease morbidity—namely disability, depression, type 2 diabetes, cardiovascular disease, certain cancers—and mortality. Childhood obesity in the same conditions, with premature onset, or with greater likelihood in adulthood 6. Thus, the economic and psychosocial costs of obesity alone, as well as when coupled with these comorbidities and sequealae, are striking. In this article, we outline the prevalence and trends of obesity, then review the myriad risk factors to which a preventive eye must be turned, and finally present the costs of obesity in terms of its morbidity, mortality, and economic burden.
Abdominal adiposity is thought to be primarily visceral, metabolically active fat surrounding the organs, and is associated with metabolic dysregulation, predisposing individuals to cardiovascular disease and related conditions 8. In children, body weight classifications Table 1 differ from those of adults because body composition varies greatly as develops, and further varies between boys and girls primarily owing to differences in sexual development and maturation.
The World Health Organization WHO Child Growth Standards are the most widely currently used classification system of weight and height status for children from birth to 5 years old, based on data from children in six regions across the globe born and raised in optimal conditions The first indications that obesity was taking on epidemic proportions originated in the USA and Europe.
With few restrictions on access to or availability of food, the prevalence of overweight and obesity in the USA climbed virtually unmitigated over the last 50 years. Trends in age-adjusted prevalence of overweight, obesity, and extreme obesity in US adults, aged 20—74 years, — Data derived are derived from Ogden, et Dominant women photos. A systematic review of national and regional surveys conducted between and points to obesity rates as low as 4.
Regional trends within Europe are apparent, with southern Italy and southern Spain, and Eastern European countries showing higher prevalence of obesity than countries in Western and Northern Europe US children may be faring better than their adult counterparts in some ways 16potentially offsetting earlier dire predictions of rampant obesity by 5. Again, as in their adult counterparts, certain sub-populations appear to be faring worse than others, notably Hispanic girls and Dominant women photos boys, in whom overweight, obesity, and class 2 obesity have increased ificantly Childhood obesity prevalence varies considerably between and within countries as well.
Researchers continued to observe the trend of north-south and west-east gradients evident in adults, with the highest levels of overweight in southern European countries The data discussed above focus on the USA and European countries, many with robust national health surveillance programs. While historical data tends to be scarcer outside of these regions, an alarming picture has emerged over the last decades in low- and middle-income countries around the globe, complicated by rapidly changing socioeconomic environments. While the USA still may boast the largest absolute s of overweight and obese individuals, several other nations exceed the USA in terms of overall prevalence and, moreover, the rate of growth in certain countries is disheartening.
For example, the prevalence of overweight and obesity in nationally representative Mexican adults was estimated to be These trends are also evident in countries outside of the Americas. From left to right, each column represents the estimated regional prevalence of overweight and obesity for,, and For a given region, a dark gray column indicates the lowest estimated prevalence in the trend, while the highest estimated prevalence is indicated by a black column.
As is evident, the vast majority of regions demonstrate the lowest estimated prevalence of overweight and obesity inand the highest indemonstrating the global reach of obesity. Asterisks denotes high income. Data are sourced from Stevens, et al. Obesity arises as the result of an energy imbalance between calories consumed and the calories expended, creating an energy surplus and a state of positive energy balance resulting in excess body weight.
This energy imbalance is partially a result of profound social and economic changes at levels well beyond the control of any single individual. And yet, not all of us living in obesogenic environments experience the same growth in our waistlines. So while body weight regulation is and should be viewed as a complex interaction between environmental, socioeconomic, and genetic factors, ultimately, personal behaviors in response to these conditions continue to play a dominant role in preventing obesity.
Importantly, apart from genetics, every risk factor discussed below is modifiable. Although genetics undoubtedly play a role, this relatively small difference in BMI, coupled with the dramatic rise in obesity over the last half century in developed and developing nations alike point to obesity risk factors beyond genetics. Nevertheless, these types of interactions have so far been investigated in relatively few genetic risk loci out of millions, and with just a handful of environmental factors, raising important questions of how to aggregate this complexity for public health and ultimately personalized medicine.
In addition, parental diet, lifestyle, and other exposures have been implicated in subsequent offspring obesity risk, including famine exposure 30parental obesity 31 — 33smoking 34Dominant women photos and other chemicals 3536and weight gain during gestation and gestational diabetes 33 Careful management of diet and lifestyle in pre- and perinatal periods could exert a considerable impact on the obesity epidemic for generations to come In the decades preceding the 21st century, the vast majority of research on obesity risk factors focused on individual-level, largely modifiable behaviors.
Caloric intake and expenditure needed for weight maintenance or healthy growth has historically taken center stage 39and caloric restriction remains today a primary focus of most popular and clinical weight-management and weight-loss approaches. Beyond overall caloric intake to regulate body weight, a tremendous amount of research has attempted to resolve the roles of diet quality and dietary patterns, including those specifying combinations of macronutrients Evidence from clinical trials have almost universally shown that caloric restriction, regardless of Dominant women photos pattern, is associated with better weight outcomes For example, research in US health professionals pointed to averaged 4-year weight gain throughout middle age as being strongly associated with increasing intake of potato chips and potatoes, sugar-sweetened beverages, and processed and unprocessed red meats, but inversely associated with the intake of vegetables, fruits, whole grains, nuts, and yogurt Specific food groups, such as sugar-sweetened beverages, have received considerable attention largely because added sugar consumption primarily as sugar-sweetened beverages has been rising concomitantly with prevalent obesity Indeed, the weight of the evidence Dominant women photos the role of sugar-sweetened beverages in obesity 4647 is a strong impetus for public health interventions and policies, such as limiting advertising on these beverages as in Mexico 48attempts to limit beverage sizes permitted for sale as in New York City 49taxation, eliminating sale in schools, etc.
Personal behaviors beyond diet physical activity, sleep, sedentary and screen time, and stress have also been independently associated with weight change and maintenance in adulthood. Recently reviewed evidence from randomized trials and observational studies support US recommendations for weight management 50consistently showing that in general, — minutes per week of moderate intensity activity is required to prevent weight gain, or aid in weight loss when accompanied by dietary restriction Income has had a shifting role in obesity risk over the last century.
As late as the midth century, the USA and Europe could link wealth directly with obesity—the wealthier an individual, the more likely to be overweight. Over the last few decades, however, perhaps owing to the abundance of cheap and highly available food, coupled with changing sociocultural norms, this link has flipped. Today, wealth in the USA tends to be inversely correlated with obesity, and it is those who are at or below the level of poverty who appear to have the highest rates of obesity Indeed, in US cities where the homeless are surveyed, the prevalence of overweight and obesity parallels that of non-homeless populations, contrary to our typical beliefs about thinness accompanying food insecurity or homelessness 60 In men, too, those in low income strata tended to have higher prevalence of obesity, but the gradient for overweight reversed in about half of the countries surveyed.
That is, in some countries, poverty was associated with more prevalent overweight than wealth, but in others, lower income was associated with more favorable weight status. The differences between sexes in terms of income status and obesity, in particular the trend reversal in men, may be in part due to low-paying jobs typically involving more physically demanding work performed by men more than by women As wealth rises in low- and middle-income countries, it is expected for poverty-obesity patterns to begin more closely mimicking those of high-income countries.
Evidence of this transition is already accumulating. This suggests that in currently transitioning economies, education may offset the apparently negative effects of increasing purchasing power in emerging obesogenic environments. However, the protective effect of education has yet to be seen in the poorer countries, such as India, Nigeria, and Benin, where both education and wealth were directly associated with increased odds of obesity The glimmer of hope, then, is that in the context of a paradigm of diseases of affluence, in which the transition to wealth seem to invariably lead to higher obesity and thus greater chronic disease burden, higher education levels may yet offset some of the frightening challenges that lay before us.
Research on the built environment tends to focus on a few measurable characteristics of neighborhoods as they relate to weight status, while holding sociodemographic and other person-level characteristics constant. Such neighborhood characteristics range from more concrete factors e.
Most studies of the built environment have been cross-sectional, tending to focus on one or two characteristics; thus, findings on the relative importance or effects of given characteristics on obesity have been inconsistent 66 — 72revealing the fundamental challenge of teasing out whether neighborhood characteristics play a causal role in weight status, or whether health-minded folks inhabit health-friendly areas to Dominant women photos with residential selection bias However, the emerging picture points to the primacy of diet-related built environments over those associated with physical activity.
While presence of neighborhood physical activity or recreational spaces has been associated with increased physical activity levels or energy expenditure 7172healthy food environments, characterized by availability of produce or presence of supermarkets over convenience stores or fast food restaurants, play a potentially more important role 687074 There is an unmet need for standardized measures, definitions, and criteria, established residential and occupational geographic radii relevant to health, and research methodologies that can take into the complexity of something as seemingly simple as a neighborhood.
Growing evidence from animal and human studies indicates that obesity may be attributable to infection, or that obesity itself may be a contagion. Infectious agents include viruses, the trillions of microbiota inhabiting the human gut, and, of course, obese humans as infectious agents themselves. Although several viruses have been identified as potentially having a causal role in obesity 76Ad is among the most studied, being causally associated with adiposity in animals.
Studies in diverse human populations generally support greater Ad viral lo as probably causal of obesity in both children and adults 76 — 79with links to other metabolic traits 77 Ground-breaking research in the last decade has emerged on the role of trillions of gut bacteria—the human microbiome—in relation to obesity, energy metabolism, and carbohydrate and lipid digestion, opening promising therapeutic avenues for obesity and disease Two primary phyla of bacteria differ in their proportions in lean vs.
Broad and sometimes dramatic changes in microbiome populations have been catalogued following gastric bypass surgery 80and in both the short- 8283 and long-term 8183 in response to changes in dietary composition Research in mice indicates that increased adiposity is a transmissible trait via microbiome transplantation 84and has prompted similar experimental fecal transplantation research in humans for the promotion of weight loss In addition, other research has examined the feeding of pre- and probiotics as therapeutic modalities deed to manipulate the gut microbiome; these strategies also show promise for a range of conditions Finally, the importance of social networks—real and virtual—in obesity is a fascinating, relatively new area of research that capitalizes on known characteristics of infectious disease transmission.
This was a stronger risk ratio than that observed between pairs of adult siblings or even between spouses. Conversely, it may be possible to capitalize on the social contagion of obesity in the reverse direction, that is, in the promotion of healthy weight and behavior. Intervention studies of weight loss often include a social-relational component, although the evidence supporting any single approach or its efficacy is relatively scarce In theory, a supportive network, community, or coaching relationship is supposed to improve weight loss; despite a lack of strong evidence, it is a key component of many popular commercial e.
Obesity is associated with concomitant or increased risk of nearly every chronic condition, from diabetes, to dyslipidemia, to poor mental health. Its impacts on risk of stroke and cardiovascular disease, certain cancers, and osteoarthritis are ificant. Many long-term cohort studies, as well as three recent major syntheses of pooled data from established cohorts 89 — 91which adequately ed for history of smoking and chronic disease status, unequivocally show that overweight and obesity over the life course is associated with excess risk of total mortality, death from cardiovascular disease, diabetes, cancer, or accidental death 89 — Indeed, the role of excess adiposity in old age is unclear.
Overweight raises risk of developing type 2 diabetes by a factor of three, and obesity by a factor of seven, compared to normal weight Excess weight in childhood and in young adulthood, and weight gain through early to mid-adulthood are strong risk factors for diabetes —Dominant women photos
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