Obesity

Obesity
Classification and external resources
Silhouettes and waist circumferences representing normal, overweight, and obese
10	E66
9	278
OMIM	601665
DiseasesDB	9099
MedlinePlus	003101
eMedicine	med/1653
MeSH	C23.888.144.699.500

Obesity is a [3]

Obesity increases the likelihood of [6]

[8]

Obesity is a leading [10]

Contents 1 Classification 2 Effects on health 2.1 Mortality 2.2 Morbidity 2.3 Survival paradox 3 Causes 3.1 Diet 3.2 Sedentary lifestyle 3.3 Genetics 3.4 Other illnesses 3.5 Social determinants 3.6 Infectious agents 4 Pathophysiology 5 Public health 6 Management 7 Epidemiology 8 History 8.1 Etymology 8.2 Historical trends 8.3 The arts 9 Society and culture 9.1 Economic impact 9.2 Size acceptance 10 Childhood obesity 11 In other animals 12 Notes 13 Further reading

Classification

Obesity is a [13]

In children, a healthy weight varies with age and sex. Obesity in children and adolescents is defined not as an absolute number but in relation to a historical normal group, such that obesity is a BMI greater than the 95th [15]

BMI	Classification
< 18.5	underweight
18.5–24.9	normal weight
25.0–29.9	overweight
30.0–34.9	class I obesity
35.0–39.9	class II obesity
? 40.0	class III obesity

BMI is calculated by dividing the subject’s mass by the square of his or her height, typically expressed either in US “customary” units:

Metric:

US customary and imperial:

where is the subject’s weight in pounds and is the subject’s height in inches.

The most commonly used definitions, established by the World Health Organization (WHO) in 1997 and published in 2000, provide the values listed in the table at right.^[3]

Some modifications to the WHO definitions have been made by particular bodies. The surgical literature breaks down “class III” obesity into further categories whose exact values are still disputed.^[16]

• Any BMI ? 35 or 40 is severe obesity
• A BMI of ? 35 or 40–44.9 or 49.9 is morbid obesity
• A BMI of ? 45 or 50 is super obesity

As Asian populations develop negative health consequences at a lower BMI than Caucasians, some nations have redefined obesity; the Japanese have defined obesity as any BMI greater than 25^[18]

Effects on health

Excessive body [2]

Mortality

Obesity is one of the leading [22]

Morbidity

Obesity increases the risk of many physical and mental conditions. These comorbidities are most commonly shown in [29]

Complications are either directly caused by obesity or indirectly related through mechanisms sharing a common cause such as a poor diet or a sedentary lifestyle. The strength of the link between obesity and specific conditions varies. One of the strongest is the link with type 2 diabetes. Excess body fat underlies 64% of cases of diabetes in men and 77% of cases in women.^[30]

Health consequences fall into two broad categories: those attributable to the effects of increased fat mass (such as [34]

Medical field	Condition	Medical field	Condition
Cardiology	ischemic heart disease:[35] angina and myocardial infarction congestive heart failure[2] high blood pressure[2] abnormal cholesterol levels[2] deep vein thrombosis and pulmonary embolism[36]	Dermatology	stretch marks[37] acanthosis nigricans[37] lymphedema[37] cellulitis[37] hirsutism[37] intertrigo[38]
Reproductive medicine	diabetes mellitus[2] polycystic ovarian syndrome[2] menstrual disorders[2] [39] [39] birth defects[2] intrauterine fetal death[39]	Gastrointestinal	[40] fatty liver disease[2] cholelithiasis (gallstones)[2]
Neurology	stroke[2] meralgia paresthetica[41] migraines[42] carpal tunnel syndrome[43] dementia[44] idiopathic intracranial hypertension[45] multiple sclerosis[46]	Oncology[47]	ovarian colorectal pancreatic stomach cervical kidney multiple myeloma
Psychiatry	depression in women[2] social stigmatization[2]	Respirology	[4] [4] [4] increased complications during [6]
Orthopedics	gout[48] poor mobility[49] osteoarthritis[2] low back pain[50]	Nephrology	erectile dysfunction[51] urinary incontinence[52] chronic renal failure[53] hypogonadism[54] buried penis[55]

Survival paradox

Although the negative health consequences of obesity in the general population are well supported by the available evidence, health outcomes in certain subgroups seem to be improved at an increased BMI, a phenomenon known as the obesity survival paradox.^[57]

In people with heart failure, those with a BMI between 30.0 and 34.9 had lower mortality than those with a normal weight. This has been attributed to the fact that people often lose weight as they become progressively more ill.^[57]

Causes

At an individual level, a combination of excessive [67]

A 2006 review identified ten other possible contributors to the recent increase of obesity: (1) insufficient sleep, (2) endocrine disruptors (environmental pollutants that interfere with lipid metabolism), (3) decreased variability in ambient temperature, (4) decreased rates of smoking, because smoking suppresses appetite, (5) increased use of medications that can cause weight gain (e.g., atypical antipsychotics), (6) proportional increases in ethnic and age groups that tend to be heavier, (7) pregnancy at a later age (which may cause susceptibility to obesity in children), (8) epigenetic risk factors passed on generationally, (9) natural selection for higher BMI, and (10) assortative mating leading to increased concentration of obesity risk factors (this would increase the number of obese people by increasing population variance in weight).^[68] While there is substantial evidence supporting the influence of these mechanisms on the increased prevalence of obesity, the evidence is still inconclusive, and the authors state that these are probably less influential than the ones discussed in the previous paragraph.

Diet

The per capita [71]

The widespread availability of [79]

As societies become increasingly reliant on [81]

Agricultural policy and techniques in the United States and Europe have led to lower food prices. In the United States, subsidization of corn, soy, wheat, and rice through the U.S. farm bill has made the main sources of processed food cheap compared to fruits and vegetables.^[82]

Obese people consistently under-report their food consumption as compared to people of normal weight.^[84] and by direct observation.

Sedentary lifestyle

A [91]

In both children and adults, there is an association between television viewing time and the risk of obesity.^[95]

Genetics

Like many other medical conditions, obesity is the result of an interplay between genetic and environmental factors. [99]

Obesity is a major feature in several syndromes, such as [101]

Studies that have focused on inheritance patterns rather than on specific genes have found that 80% of the offspring of two obese parents were also obese, in contrast to less than 10% of the offspring of two parents who were of normal weight.^[102]

The [105]

Other illnesses

Certain physical and mental illnesses and the pharmaceutical substances used to treat them can increase risk of obesity. Medical illnesses that increase obesity risk include several rare genetic syndromes (listed above) as well as some congenital or acquired conditions: [108]

Certain medications may cause weight gain or changes in body composition; these include insulin, sulfonylureas, thiazolidinediones, atypical antipsychotics, antidepressants, steroids, certain anticonvulsants (phenytoin and valproate), pizotifen, and some forms of hormonal contraception.^[2]

Social determinants

While genetic influences are important to understanding obesity, they cannot explain the current dramatic increase seen within specific countries or globally.^[109] Though it is accepted that energy consumption in excess of energy expenditure leads to obesity on an individual basis, the cause of the shifts in these two factors on the societal scale is much debated. There are a number of theories as to the cause but most believe it is a combination of various factors.

The correlation between [112]

Many explanations have been put forth for associations between BMI and social class. It is thought that in developed countries, the wealthy are able to afford more nutritious food, they are under greater social pressure to remain slim, and have more opportunities along with greater expectations for [115]

Smoking has a significant effect on an individual’s weight. Those who quit smoking gain an average of 4.4 kilograms (9.7 lb) for men and 5.0 kilograms (11.0 lb) for women over ten years.^[117]

In the United States the number of children a person has is related to their risk of obesity. A woman’s risk increases by 7% per child, while a man’s risk increases by 4% per child.^[119]

In the developing world urbanization is playing a role in increasing rate of obesity. In China overall rates of obesity are below 5%; however, in some cities rates of obesity are greater than 20%.^[120]

[121]

Consistent with cognitive epidemiological data, numerous studies confirm that obesity is associated with cognitive deficits.^[122] Whether obesity causes cognitive deficits, or vice versa is unclear at present.

Infectious agents

The study of the effect of infectious agents on metabolism is still in its early stages. Gut flora has been shown to differ between lean and obese humans. There is an indication that gut flora in obese and lean individuals can affect the metabolic potential. This apparent alteration of the metabolic potential is believed to confer a greater capacity to harvest energy contributing to obesity. Whether these differences are the direct cause or the result of obesity has yet to be determined unequivocally.^[123]

An association between viruses and obesity has been found in humans and several different animal species. The amount that these associations may have contributed to the rising rate of obesity is yet to be determined.^[124]

Pathophysiology

Flier summarizes the many possible pathophysiological mechanisms involved in the development and maintenance of obesity.^[125] This field of research had been almost unapproached until leptin was discovered in 1994. Since this discovery, many other hormonal mechanisms have been elucidated that participate in the regulation of appetite and food intake, storage patterns of adipose tissue, and development of insulin resistance. Since leptin’s discovery, ghrelin, insulin, orexin, PYY 3-36, cholecystokinin, adiponectin, as well as many other mediators have been studied. The adipokines are mediators produced by adipose tissue; their action is thought to modify many obesity-related diseases.

Leptin and ghrelin are considered to be complementary in their influence on appetite, with ghrelin produced by the stomach modulating short-term appetitive control (i.e. to eat when the stomach is empty and to stop when the stomach is stretched). Leptin is produced by adipose tissue to signal fat storage reserves in the body, and mediates long-term appetitive controls (i.e. to eat more when fat storages are low and less when fat storages are high). Although administration of leptin may be effective in a small subset of obese individuals who are leptin deficient, most obese individuals are thought to be leptin resistant and have been found to have high levels of leptin.^[125]

While leptin and ghrelin are produced peripherally, they control appetite through their actions on the [127]

The arcuate nucleus contains two distinct groups of [125]

Public health

The [133]

Many countries and groups have published reports pertaining to obesity. In 1998 the first US Federal guidelines were published, titled “Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: The Evidence Report”.^[135]

In 2004, the United Kingdom [139]

Comprehensive approaches are being looked at to address the rising rates of obesity. The Obesity Policy Action (OPA) framework divides measure into ‘upstream’ policies, ‘midstream’ policies, ‘downstream’ policies. ‘Upstream’ policies look at changing society, ‘midstream’ policies try to alter individuals’ behavior to prevent obesity, and ‘downstream’ policies try to treat currently afflicted people.^[140]

Management

The main treatment for obesity consists of [145]

One medication, [149]

The most effective treatment for obesity is [150] However, due to its cost and the risk of complications, researchers are searching for other effective yet less invasive treatments.

Epidemiology

Before the 20th century, obesity was rare;^[156]

Once considered a problem only of high-income countries, obesity rates are rising worldwide and affecting both the developed and developing world.^[2]

History

Etymology

Obesity is from the [158]

Historical trends

The [162]

With the onset of the [2]

Many cultures throughout history have viewed obesity as the result of a character flaw. The obesus or fat character in [164]

Public perceptions in Western society regarding healthy body weight differ from those regarding the weight that is considered ideal  – and both have changed since the beginning of the 20th century. The weight that is viewed as an ideal has become lower since the 1920s. This is illustrated by the fact that the average height of Miss America pageant winners increased by 2% from 1922 to 1999, while their average weight decreased by 12%.^[166]

Obesity is still seen as a sign of wealth and well-being in many parts of Africa. This has become particularly common since the HIV epidemic began.^[2]

The arts

The first sculptural representations of the human body 20,000–35,000 years ago depict obese females. Some attribute the [10]

During the [10]

Society and culture

Economic impact

In addition to its health impacts, obesity leads to many problems including disadvantages in employment^[169] and increased business costs. These effects are felt by all levels of society from individuals, to corporations, to governments.

In 2005, the medical costs attributable to obesity in the US were an estimated $190.2 billion or 20.6% of all medical expenditures,^[174]

Obesity prevention programs have been found to reduce the cost of treating obesity-related disease. However, the longer people live, the more medical costs they incur. Researchers therefore conclude that reducing obesity may improve the public’s health, but it is unlikely to reduce overall health spending.^[175]

Obesity can lead to social stigmatization and disadvantages in employment.^[179]

Some research shows that obese people are less likely to be hired for a job and are less likely to be promoted.^[180]

Specific industries, such as the airline, healthcare and food industries, have special concerns. Due to rising rates of obesity, airlines face higher fuel costs and pressures to increase seating width.^[184]

Size acceptance

The principal goal of the fat acceptance movement is to decrease discrimination against people who are overweight and obese.^[187]

A number of organizations exist that promote the acceptance of obesity. They have increased in prominence in the latter half of the 20th century.^[190]

The [187]

Childhood obesity

The healthy BMI range varies with the age and sex of the child. Obesity in children and adolescents is defined as a BMI greater than the 95th [192]

As with obesity in adults, many different factors contribute to the rising rates of childhood obesity. Changing diet and decreasing physical activity are believed to be the two most important in causing the recent increase in the rates.^[192]

In other animals

Obesity in pets is common in many countries. Rates of overweight and obesity in dogs in the United States range from 23 to 41% with about 5.1% obese.^[197]

Notes

References

Further reading

Find more about Obesity on Wikipedia’s sister projects
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v t e 260–269) Hypoalimentation/ malnutrition Protein-energy malnutrition Catabolysis Avitaminosis B vitamins B1: Vitamin B12 deficiency Other vitamins A: Vitamin K deficiency Mineral deficiency Keshan disease) Hyperalimentation Overweight · Obesity Childhood obesity · Obesity hypoventilation syndrome · Abdominal obesity Vitamin poisoning Hypervitaminosis E Mineral overload see toxicity NUT met met drug(12)

Source: Wikipedia