Obesity/ja: Difference between revisions

Obesity increases the risk of many physical and mental conditions. These comorbidities are most commonly shown in [[metabolic syndrome]], a combination of medical disorders which includes: [[diabetes mellitus type 2]], [[hypertension|high blood pressure]], [[hypercholesterolemia|high blood cholesterol]], and [[hypertriglyceridemia|high triglyceride levels]]. A study from the [[RAK Hospital]] found that obese people are at a greater risk of developing [[long COVID]]. The CDC has found that obesity is the single strongest risk factor for severe COVID-19 illness.

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.

Health consequences fall into two broad categories: those attributable to the effects of increased fat mass (such as [[osteoarthritis]], [[obstructive sleep apnea]], social stigmatization) and those due to the increased number of [[fat cells]] ([[diabetes mellitus|diabetes]], [[cancer]], [[cardiovascular disease]], [[non-alcoholic fatty liver disease]]). Increases in body fat alter the body's response to insulin, potentially leading to [[insulin resistance]]. Increased fat also creates a [[inflammation|proinflammatory state]], and a [[thrombosis|prothrombotic]] state.

! Medical field

! Condition

! Medical field

! Condition

| width="10%" | [[Cardiology]]

* [[Coronary heart disease]]: [[angina pectoris|angina]] and [[myocardial infarction]]

* [[Congestive heart failure]]

* [[High blood pressure]]

* [[Dyslipidemia|Abnormal cholesterol levels]]

* [[Deep vein thrombosis]] and [[pulmonary embolism]]

| [[Dermatology]]

* [[Acanthosis nigricans]]

* [[Lymphedema]]

* [[Cellulitis]]

* [[Hirsutism]]

* [[Intertrigo]]

| [[Endocrinology]] and [[reproductive medicine]]

* [[Diabetes mellitus]]

* [[Polycystic ovarian syndrome]]

* [[menstruation|Menstrual]] disorders

* [[Infertility]]

* [[Maternal obesity|Complications during pregnancy]]

* [[Birth defects]]

* [[Stillbirth|Intrauterine fetal death]]

| <!--Alphabetized-->[[Gastroenterology]]

* [[Gastroesophageal reflux disease]]

* [[Non-alcoholic fatty liver disease|Fatty liver disease]]

* [[Cholelithiasis]] (gallstones)

| [[Neurology]]

* [[Stroke]]

* [[Meralgia paresthetica]]

* [[Migraines]]

* [[Carpal tunnel syndrome]]

* [[Dementia]]

* [[Idiopathic intracranial hypertension]]

* [[Multiple sclerosis]]

| [[Oncology]]

* [[esophageal cancer|Esophageal]]

* [[colorectal cancer|Colorectal]]

* [[pancreatic cancer|Pancreatic]]

* [[Gallbladder cancer|Gallbladder]]

* [[Endometrial cancer|Endometrial]]

* [[Renal cell carcinoma|Kidney]]

* [[Leukemia]]

* [[Hepatocellular carcinoma]]

* [[Malignant melanoma]]

| style="width:10%;" |[[Psychiatry]]

* [[Major depressive disorder|Depression]] in women

* Social [[Social stigma|stigmatization]]

| [[Respirology]]

* [[Sleep apnea|Obstructive sleep apnea]]

* [[Obesity hypoventilation syndrome]]

* [[Asthma]]

* Increased complications during [[general anaesthesia]]

* increased risk of severe COVID-19

| [[Rheumatology]] and [[orthopedics]]

* [[Gout]]

* Poor mobility

* [[Osteoarthritis]]

* [[Low back pain]]

| [[Urology]] and [[Nephrology]]

* [[Erectile dysfunction]]

* [[Urinary incontinence]]

* [[Chronic renal failure]]

* [[Hypogonadism]]

* [[Buried penis]]

==== Metrics of health ====

{{Main|Metabolically healthy obesity}}

Newer research has focused on methods of identifying healthier obese people by clinicians, and not treating obese people as a monolithic group. Obese people who do not experience medical complications from their obesity are sometimes called ''[[metabolically healthy obese|(metabolically) healthy obese]]'', but the extent to which this group exists (especially among older people) is in dispute. The number of people considered ''metabolically healthy'' depends on the definition used, and there is no universally accepted definition. There are numerous obese people who have relatively few metabolic abnormalities, and a minority of obese people have no medical complications. The guidelines of the [[American Association of Clinical Endocrinologists]] call for physicians to use [[risk stratification]] with obese patients when considering how to assess their risk of developing type 2 diabetes.

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In 2014, the BioSHaRE–[[European Union|EU]] Healthy Obese Project (sponsored by Maelstrom Research, a team under the [[Research Institute of the McGill University Health Centre]]) came up with two definitions for ''healthy obesity'', one more strict and one less so:

|+BioSHaRE Healthy Obese (HOP) Project Criteria (2014)<br />{{Nobold|A patient must have a [[body mass index]] ≥ 30, and all of the following:}}

!Less strict

!More strict

! colspan="3" |[[Blood pressure]] measured as follows, with no pharmaceutical help

!Overall ([[mmHg]])

![[Systolic]] (mmHg)

![[Diastolic]] (mmHg)

! colspan="3" |[[Blood sugar level]] measured as follows, with no pharmaceutical help

!Blood glucose ([[mmol]]/[[Litre|L]])

! colspan="3" |[[Triglycerides]] measured as follows, with no pharmaceutical help

!Fasting (mmol/L)

!Non-fasting (mmol/L)

! colspan="3" |[[High-density lipoprotein]] measured as follows, with no pharmaceutical help

!Men (mmol/L)

!Women (mmol/L)

! colspan="3" |No diagnosis of any [[cardiovascular disease]]

Another identification metric for health in obese people is [[Triceps surae muscle|calf]] [[Muscle strength|strength]], which is positively correlated with [[physical fitness]] in obese people. [[Body composition]] in general is hypothesized to help explain the existence of metabolically healthy obesity—the metabolically healthy obese are often found to have low amounts of [[Ectopia (medicine)|ectopic]] fat (fat stored in tissues other than adipose tissue) despite having overall fat mass equivalent in weight to obese people with [[metabolic syndrome]].

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===Survival paradox===

{{See also|Obesity paradox}}

Although the negative health consequences of obesity in the general population are well supported by the available research evidence, health outcomes in certain subgroups seem to be improved at an increased BMI, a phenomenon known as the obesity survival paradox. The paradox was first described in 1999 in overweight and obese people undergoing [[hemodialysis]] and has subsequently been found in those with [[heart failure]] and [[Peripheral vascular disease|peripheral artery disease]] (PAD).

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. Similar findings have been made in other types of heart disease. People with class I obesity and heart disease do not have greater rates of further heart problems than people of normal weight who also have heart disease. In people with greater degrees of obesity, however, the risk of further cardiovascular events is increased. Even after [[Coronary artery bypass surgery|cardiac bypass surgery]], no increase in mortality is seen in the overweight and obese. One study found that the improved survival could be explained by the more aggressive treatment obese people receive after a cardiac event. Another study found that if one takes into account [[chronic obstructive pulmonary disease]] (COPD) in those with PAD, the benefit of obesity no longer exists.

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==Causes==

The "[[a calorie is a calorie]]" model of obesity posits a combination of excessive [[food energy]] intake and a lack of [[physical activity]] as the cause of most cases of obesity. A limited number of cases are due primarily to genetics, medical reasons, or psychiatric illness. In contrast, increasing rates of obesity at a societal level are felt to be due to an easily accessible and palatable diet, increased [[Effects of the car on societies|reliance on cars]], and mechanized manufacturing.

Some other factors have been proposed as causes towards rising rates of obesity worldwide, including [[sleep debt|insufficient sleep]], [[endocrine disruptor]]s, increased usage of certain medications (such as [[atypical antipsychotics]]), increases in ambient temperature, decreased rates of [[tobacco smoking|smoking]], demographic changes, increasing maternal age of first-time mothers, changes to [[epigenetic]] dysregulation from the environment, increased phenotypic variance via [[assortative mating]], social pressure to [[dieting|diet]], among others. According to one study, factors like these may play as big of a role as excessive food energy intake and a lack of physical activity; however, the relative magnitudes of the effects of any proposed cause of obesity is varied and uncertain, as there is a general need for randomized controlled trials on humans before definitive statement can be made.

According to the [[Endocrine Society]], there is "growing evidence suggesting that obesity is a disorder of the [[energy homeostasis]] system, rather than simply arising from the passive accumulation of excess weight".

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===Diet===

<div class="thumbimage">[[File:World map of calory consumption 1961 (v2).svg|200px|alt=(Left) A world map with countries colored to reflect the food energy consumption of their people in 1961. North America, Europe, and Australia have relatively high intake, while Africa and Asia consume much less.]]

<div class="thumbimage">[[File:World map of Energy consumption 2001-2003.svg|200px|alt=(Right) A world map with countries colored to reflect the food energy consumption of their people in 2001–2003. Consumption in North America, Europe, and Australia has increased with respect to previous levels in 1971. Food consumption has also increased substantially in many parts of Asia. However, food consumption in Africa remains low.]]

</div><div class="thumbcaption" style="clear: left; text-align: left; background: transparent">Map of dietary energy availability per person per day in 1961 (left) and 2001–2003 (right) Calories per person per day (kilojoules per person per day)

[[File:World Per Person Energy Consumption.png|thumb|upright=1.6|alt=A graph showing a gradual increase in global food energy consumption per person per day between 1961 and 2002.|Average per capita energy consumption of the world from 1961 to 2002]]

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Excess appetite for palatable, high-calorie food (especially fat, sugar, and certain animal proteins) is seen as the primary factor driving obesity worldwide, likely because of imbalances in neurotransmitters affecting the drive to eat. [[Dietary energy supply]] per capita varies markedly between different regions and countries. It has also changed significantly over time. From the early 1970s to the late 1990s the average [[food energy]] available per person per day (the amount of food bought) increased in all parts of the world except Eastern Europe. The United States had the highest availability with {{convert|3654|Cal}} per person in 1996. This increased further in 2003 to {{convert|3754|Cal}}. During the late 1990s, Europeans had {{convert|3394|Cal}} per person, in the developing areas of Asia there were {{convert|2648|Cal}} per person, and in sub-Saharan Africa people had {{convert|2176|Cal}} per person. Total food energy consumption has been found to be related to obesity.

[[File:Prevalence Of Obesity In The Adult Population By Region.svg|thumb|Prevalence of obesity in the adult population by region (2000 - 2016)|330x330px]]

The widespread availability of [[Dietary Guidelines for Americans|dietary guidelines]] has done little to address the problems of overeating and poor dietary choice. From 1971 to 2000, obesity rates in the United States increased from 14.5% to 30.9%. During the same period, an increase occurred in the average amount of food energy consumed. For women, the average increase was {{convert|335|Cal}} per day ({{convert|1542|Cal}} in 1971 and {{convert|1877|Cal}} in 2004), while for men the average increase was {{convert|168|Cal}} per day ({{convert|2450|Cal}} in 1971 and {{convert|2618|Cal}} in 2004). Most of this extra food energy came from an increase in carbohydrate consumption rather than fat consumption. The primary sources of these extra carbohydrates are sweetened beverages, which now account for almost 25 percent of daily food energy in young adults in America, and potato chips. Consumption of [[sweetened beverages]] such as soft drinks, fruit drinks, and iced tea is believed to be contributing to the rising rates of obesity and to an increased risk of metabolic syndrome and type 2 diabetes. [[Vitamin D deficiency]] is related to diseases associated with obesity.

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As societies become increasingly reliant on [[food energy|energy-dense]], big-portions, and [[Fast food|fast-food]] meals, the association between fast-food consumption and obesity becomes more concerning. In the United States, consumption of fast-food meals tripled and food energy intake from these meals quadrupled between 1977 and 1995.

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[[Agricultural policy]] and [[Green Revolution (agriculture)|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. [[Calorie count laws]] and [[nutrition facts label]]s attempt to steer people toward making healthier food choices, including awareness of how much food energy is being consumed.

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Obese people consistently under-report their food consumption as compared to people of normal weight. This is supported both by tests of people carried out in a [[calorimeter]] room and by direct observation.

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In both children and adults, there is an association between television viewing time and the risk of obesity. Increased media exposure increases the rate of childhood obesity, with rates increasing proportionally to time spent watching television.

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[[File:La monstrua desnuda (1680), de Juan Carreño de Miranda..jpg|thumb|upright=1.3|alt=A painting of a dark haired pink cheeked obese nude young female leaning against a table. She is holding grapes and grape leaves in her left hand which cover her genitalia.|"La Monstrua Desnuda" (The Nude Monster), an 1680 painting by [[Juan Carreno de Miranda]] of a girl presumed to have [[Prader–Willi syndrome]]]]

Like many other medical conditions, obesity is the result of an interplay between genetic and environmental factors. [[Polymorphism (biology)|Polymorphisms]] in various [[gene]]s controlling [[appetite]] and [[metabolism]] predispose to obesity when sufficient food energy is present. As of 2006, more than 41 of these sites on the human genome have been linked to the development of obesity when a favorable environment is present. People with two copies of the [[FTO gene]] (fat mass and obesity associated gene) have been found on average to weigh 3–4&nbsp;kg more and have a 1.67-fold greater risk of obesity compared with those without the risk [[allele]]. The differences in BMI between people that are [[heritability|due to genetics]] varies depending on the population examined from 6% to 85%.

Obesity is a major feature in several syndromes, such as [[Prader–Willi syndrome]], [[Bardet–Biedl syndrome]], [[Cohen syndrome]], and [[MOMO syndrome]]. (The term "non-syndromic obesity" is sometimes used to exclude these conditions.) In people with early-onset severe obesity (defined by an onset before 10&nbsp;years of age and body mass index over three [[standard deviation]]s above normal), 7% harbor a single point DNA mutation.

Studies that have focused on inheritance patterns rather than on specific genes have found that 80% of the offspring of two [[parental obesity|obese parents]] were also obese, in contrast to less than 10% of the offspring of two parents who were of normal weight. Different people exposed to the same environment have different risks of obesity due to their underlying genetics.

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The [[thrifty gene hypothesis]] postulates that, due to dietary scarcity during human evolution, people are prone to obesity. Their ability to take advantage of rare periods of abundance by storing energy as fat would be advantageous during times of varying food availability, and individuals with greater adipose reserves would be more likely to survive [[famine]]. This tendency to store fat, however, would be maladaptive in societies with stable food supplies. This theory has received various criticisms, and other evolutionarily-based theories such as the [[drifty gene hypothesis]] and the [[thrifty phenotype|thrifty phenotype hypothesis]] have also been proposed.

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===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: [[hypothyroidism]], [[Cushing's syndrome]], [[growth hormone deficiency]], and some [[eating disorder]]s such as [[binge eating disorder]] and [[night eating syndrome]]. However, obesity is not regarded as a psychiatric disorder, and therefore is not listed in the [[Diagnostic and Statistical Manual of Mental Disorders|DSM-IVR]] as a psychiatric illness. The risk of overweight and obesity is higher in patients with psychiatric disorders than in persons without psychiatric disorders. Obesity and [[Depression (mood)|depression]] influence each other mutually, with obesity increasing the risk of clinical depression, and also depression leading to a higher chance of developing obesity.

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=== Drug-induced obesity ===

Certain medications may cause weight gain or changes in [[body composition]]; these include [[insulin]], [[sulfonylurea]]s, [[thiazolidinedione]]s, [[atypical antipsychotic]]s, [[antidepressant]]s, [[glucocorticoids|steroids]], certain [[anticonvulsant]]s ([[phenytoin]] and [[valproate]]), [[pizotifen]], and some forms of [[hormonal contraception]].

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The correlation between [[social class]] and BMI varies globally. Research in 1989 found that in developed countries women of a high social class were less likely to be obese. No significant differences were seen among men of different social classes. In the developing world, women, men, and children from high social classes had greater rates of obesity. In 2007 repeating the same research found the same relationships, but they were weaker. The decrease in strength of correlation was felt to be due to the effects of [[globalization]]. Among developed countries, levels of adult obesity, and percentage of teenage children who are overweight, are correlated with [[economic inequality|income inequality]]. A similar relationship is seen among US states: more adults, even in higher social classes, are obese in more unequal states.

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 [[physical fitness]]. In [[undeveloped countries]] the ability to afford food, high energy expenditure with physical labor, and cultural values favoring a larger body size are believed to contribute to the observed patterns. Attitudes toward body weight held by people in one's life may also play a role in obesity. A correlation in BMI changes over time has been found among friends, siblings, and spouses. Stress and perceived low social status appear to increase risk of obesity.

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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%. In part, this may be because of urban design issues (such as inadequate public spaces for physical activity). Time spent in motor vehicles, as opposed to [[active transportation]] options such as cycling or walking, is correlated with increased risk of obesity.

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[[Malnutrition]] in early life is believed to play a role in the rising rates of obesity in the [[developing world]]. Endocrine changes that occur during periods of malnutrition may promote the storage of fat once more food energy becomes available.

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 people. There is an indication that gut flora can affect the metabolic potential. This apparent alteration 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. The use of [[antibiotics]] among children has also been associated with obesity later in life.

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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.

Not getting enough sleep [[sleep and weight|is also associated with obesity]]. Whether one causes the other is unclear. Even if short sleep does increase weight gain, it is unclear if this is to a meaningful degree or if increasing sleep would be of benefit.

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Some have proposed that chemical compounds called "[[obesogens]]" may play a role in obesity.

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In relation to globalization, it is known that trade liberalization is linked to obesity; research, based on data from 175 countries during 1975-2016, showed that obesity prevalence was positively correlated with trade openness, and the correlation was stronger in developing countries.

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Two distinct but related processes are considered to be involved in the development of obesity: sustained positive energy balance (energy intake exceeding energy expenditure) and the resetting of the body weight "set point" at an increased value. The second process explains why finding effective obesity treatments has been difficult. While the underlying biology of this process still remains uncertain, research is beginning to clarify the mechanisms.

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At a biological level, there are many possible [[pathophysiology|pathophysiological]] mechanisms involved in the development and maintenance of obesity. This field of research had been almost unapproached until the [[leptin]] gene was discovered in 1994 by J. M. Friedman's laboratory. While leptin and [[ghrelin]] are produced peripherally, they control appetite through their actions on the [[central nervous system]]. In particular, they and other appetite-related hormones act on the [[hypothalamus]], a region of the brain central to the regulation of food intake and energy expenditure. There are several circuits within the hypothalamus that contribute to its role in integrating appetite, the [[melanocortin]] pathway being the most well understood. The circuit begins with an area of the hypothalamus, the [[arcuate nucleus]], that has outputs to the [[lateral hypothalamus]] (LH) and [[ventromedial hypothalamus]] (VMH), the brain's feeding and satiety centers, respectively.

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The arcuate nucleus contains two distinct groups of [[neuron]]s. The first group coexpresses [[neuropeptide Y]] (NPY) and [[agouti-related peptide]] (AgRP) and has stimulatory inputs to the LH and inhibitory inputs to the VMH. The second group coexpresses [[pro-opiomelanocortin]] (POMC) and [[cocaine- and amphetamine-regulated transcript]] (CART) and has stimulatory inputs to the VMH and inhibitory inputs to the LH. Consequently, NPY/AgRP neurons stimulate feeding and inhibit satiety, while POMC/CART neurons stimulate satiety and inhibit feeding. Both groups of arcuate nucleus neurons are regulated in part by leptin. Leptin inhibits the NPY/AgRP group while stimulating the POMC/CART group. Thus a deficiency in leptin signaling, either via leptin deficiency or leptin resistance, leads to overfeeding and may account for some genetic and acquired forms of obesity.

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{{Main|Management of obesity}}

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The main treatment for obesity consists of [[weight loss]] via lifestyle interventions, including prescribed [[Diet (nutrition)|diets]] and [[physical exercise]]. Although it is unclear what diets might support long-term weight loss, and although the effectiveness of [[Calorie restriction|low-calorie diets]] is debated, lifestyle changes that reduce calorie consumption or increase physical exercise over the long term also tend to produce some sustained weight loss, despite slow weight regain over time. Although 87% of participants in the [[National Weight Control Registry]] were able to maintain 10% body weight loss for 10 years, the most appropriate dietary approach for long term weight loss maintenance is still unknown. In the US, intensive behavioral interventions combining both dietary changes and exercise are recommended. [[Intermittent fasting]] has no additional benefit of weight loss compared to continuous energy restriction. Adherence is a more important factor in weight loss success than whatever kind of diet an individual undertakes.

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Several hypo-caloric diets are effective. In the short-term [[Low-carbohydrate diet|low carbohydrate diets]] appear better than [[Low-fat diet|low fat diets]] for weight loss. In the long term, however, all types of low-carbohydrate and low-fat diets appear equally beneficial. Heart disease and diabetes risks associated with different diets appear to be similar. Promotion of the Mediterranean diets among the obese may lower the risk of heart disease. Decreased intake of [[sweet drink]]s is also related to weight-loss. Success rates of long-term weight loss maintenance with lifestyle changes are low, ranging from 2–20%. Dietary and lifestyle changes are effective in limiting excessive weight gain in [[pregnancy]] and improve outcomes for both the mother and the child. Intensive behavioral counseling is recommended in those who are both obese and have other risk factors for heart disease.

[[File:Prevalence Of Obesity In The Adult Population, Top Countries (2016).svg|thumb|330x330px|Prevalence of obesity in the adult population, top countries (2016)]]

[[File:Prevalence Of Obesity In The Adult Population (2016).svg|thumb|330x330px|Prevalence of obesity in the adult population in 2016]]

Obesity is a complex public health and policy problem because of its prevalence, costs, and health effects. As such, managing it requires changes in the wider societal context and effort by communities, local authorities, and governments. Public health efforts seek to understand and correct the [[Obesity and the environment|environmental factors]] responsible for the increasing prevalence of obesity in the population. Solutions look at changing the factors that cause excess food energy consumption and inhibit physical activity. Efforts include federally reimbursed meal programs in schools, limiting direct [[junk food|junk]] [[food marketing]] to children, and decreasing access to sugar-sweetened beverages in schools. The World Health Organization recommends the taxing of sugary drinks. When constructing urban environments, efforts have been made to increase access to parks and to develop pedestrian routes.

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[[Mass media]] campaigns seem to have limited effectiveness in changing behaviors that influence obesity, but may increase knowledge and awareness regarding physical activity and diet, which might lead to changes in the long term. Campaigns might also be able to reduce the amount of time spent [[Sedentary lifestyle|sitting or lying down]] and positively affect the intention to be active physically. [[Nutrition facts label|Nutritional labelling]] with energy information on menus might be able to help reducing energy intake while dining in restaurants. Some call for policy against [[ultra-processed foods]].

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==Medical interventions==

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{{Main|Anti-obesity medication}}

Since the introduction of medicines for the management of obesity in the 1930s, many compounds have been tried. Most of them reduce body weight by small amounts, and several of them are no longer marketed for obesity because of their side effects. Out of 25 anti-obesity medications withdrawn from the market between 1964 and 2009, 23 acted by altering the functions of chemical [[neurotransmitters]] in the brain. The most common side effects of these drugs that led to withdrawals were mental disturbances, cardiac side effects, and [[Substance abuse|drug abuse]] or [[drug dependence]]. Deaths were reportedly associated with seven products.

Five medications beneficial for long-term use are: [[orlistat]], [[lorcaserin]], [[liraglutide]], [[Phentermine/topiramate|phentermine–topiramate]], and [[naltrexone/bupropion|naltrexone–bupropion]]. They result in weight loss after one year ranged from 3.0 to 6.7&nbsp;kg (6.6-14.8&nbsp;lbs) over placebo. Orlistat, liraglutide, and naltrexone–bupropion are available in both the United States and Europe, phentermine–topiramate is available only in the United States. European regulatory authorities rejected lorcaserin and phentermine-topiramate, in part because of associations of heart valve problems with lorcaserin and more general heart and blood vessel problems with phentermine–topiramate. Lorcaserin was available in the United States and then removed from the market in 2020 due to its association with cancer. Orlistat use is associated with high rates of gastrointestinal side effects and concerns have been raised about negative effects on the kidneys. There is no information on how these drugs affect longer-term complications of obesity such as cardiovascular disease or death; however, liraglutide, when used for type 2 diabetes, does reduce cardiovascular events.

In 2019 a [[systematic review]] compared the effects on weight of various doses of [[fluoxetine]] (60&nbsp;mg/d, 40&nbsp;mg/d, 20&nbsp;mg/d, 10&nbsp;mg/d) in obese adults. When compared to placebo, all dosages of fluoxetine appeared to contribute to weight loss but lead to increased risk of experiencing side effects such as dizziness, drowsiness, fatigue, insomnia and nausea during period of treatment. However, these conclusions were from low certainty evidence. When comparing, in the same review, the effects of fluoxetine on weight of obese adults, to other [[Anorectic|anti-obesity agents]], [[Omega-3 fatty acid|omega-3]] gel and not receiving a treatment, the authors could not reach conclusive results due to poor quality of evidence.

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Among antipsychotic drugs for treating schizophrenia [[clozapine]] is the most effective, but it also has the highest risk of causing the [[metabolic syndrome]], of which obesity is the main feature. For people who gain weight because of clozapine, taking [[metformin]] may reportedly improve three of the five components of the metabolic syndrome: waist circumference, fasting glucose, and fasting triglycerides.

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The most effective treatment for obesity is [[bariatric surgery]]. The types of procedures include [[laparoscopic adjustable gastric banding]], [[Roux-en-Y gastric bypass]], [[vertical-sleeve gastrectomy]], and [[biliopancreatic diversion]]. Surgery for severe obesity is associated with long-term weight loss, improvement in obesity-related conditions, and decreased overall mortality; however, improved metabolic health results from the weight loss, not the surgery. One study found a weight loss of between 14% and 25% (depending on the type of procedure performed) at 10&nbsp;years, and a 29% reduction in all cause mortality when compared to standard weight loss measures. Complications occur in about 17% of cases and reoperation is needed in 7% of cases.

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[[File:Obesity rate.png|thumb|Share of adults with BMIs > 30 (2016)]]

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In earlier historical periods obesity was rare and achievable only by a small elite, although already recognised as a problem for health. But as prosperity increased in the [[Early Modern period]], it affected increasingly larger groups of the population. Prior to the 1970s, obesity was a relatively rare condition even in the wealthiest of nations, and when it did exist it tended to occur among the wealthy. Then, a confluence of events started to change the human condition. The average BMI of populations in first-world countries started to increase, and consequently there was a rapid increase in the proportion of people overweight and obese.

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In 1997, the WHO formally recognized obesity as a global epidemic. As of 2008, the WHO estimates that at least 500&nbsp;million adults (greater than 10%) are obese, with higher rates among women than men. The global prevalence of obesity more than doubled between 1980 and 2014. In 2014, more than 600 million adults were obese, equal to about 13 percent of the world's adult population. The percentage of adults affected in the United States as of 2015–2016 is about 39.6% overall (37.9% of males and 41.1% of females). In 2000, the [[World Health Organization]] (WHO) stated that [[overweight]] and obesity were replacing more traditional [[public health]] concerns such as [[undernutrition]] and [[infectious diseases]] as one of the most significant cause of poor health.

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==History==

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===Historical attitudes===

[[File:Charles Mellin (attributed) - Portrait of a Gentleman - Google Art Project.jpg|thumb|upright=1.0|alt=A very obese gentleman with a prominent double chin and mustache dressed in black with a sword at his left side.|During the [[Middle Ages]] and the [[Renaissance]] ''The Tuscan General [[Alessandro del Borro]]'', attributed to Charles Mellin, 1645]]

[[File:Venus von Willendorf 01.jpg|thumb|upright=1.0|alt=A carved stone miniature figurine depicted an obese female.|''[[Venus of Willendorf]]'' created 24,000–22,000 BC]]

[[Ancient Greek medicine]] recognizes obesity as a medical disorder and records that the Ancient Egyptians saw it in the same way. [[Hippocrates]] wrote that "Corpulence is not only a disease itself, but the harbinger of others". The Indian surgeon [[Sushruta]] (6th century BCE) related obesity to diabetes and heart disorders. He recommended physical work to help cure it and its side effects. For most of human history, mankind struggled with food scarcity. Obesity has thus historically been viewed as a sign of wealth and prosperity. It was common among high officials in Ancient East Asian civilizations. In the 17th century, English medical author [[Tobias Venner]] is credited with being one of the first to refer to the term as a societal disease in a published English language book.

With the onset of the [[Industrial Revolution]], it was realized that the military and economic might of nations were dependent on both the body size and strength of their soldiers and workers. Increasing the average body mass index from what is now considered underweight to what is now the normal range played a significant role in the development of industrialized societies. Height and weight thus both increased through the 19th&nbsp;century in the developed world. During the 20th century, as populations reached their genetic potential for height, weight began increasing much more than height, resulting in obesity. In the 1950s, increasing wealth in the developed world decreased child mortality, but as body weight increased, heart and kidney disease became more common.

Many cultures throughout history have viewed obesity as the result of a character flaw. The ''obesus'' or fat character in [[Ancient Greek comedy]] was a glutton and figure of mockery. During Christian times, food was viewed as a gateway to the sins of [[Sloth (deadly sin)|sloth]] and [[lust]]. In modern Western culture, excess weight is often regarded as unattractive, and obesity is commonly associated with various negative stereotypes. People of all ages can face social stigmatization and may be targeted by bullies or shunned by their peers.

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.

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===The arts===

The first sculptural representations of the human body 20,000–35,000&nbsp;years ago depict obese females. Some attribute the [[Venus figurines]] to the tendency to emphasize fertility while others feel they represent "fatness" in the people of the time. Corpulence is, however, absent in both Greek and Roman art, probably in keeping with their ideals regarding moderation. This continued through much of Christian European history, with only those of low socioeconomic status being depicted as obese.

During the [[Renaissance]] some of the upper class began flaunting their large size, as can be seen in portraits of [[Henry VIII of England]] and [[Alessandro dal Borro]]. [[Peter Paul Rubens|Rubens]] (1577–1640) regularly depicted heavyset women in his pictures, from which derives the term [[Peter Paul Rubens#Work|Rubenesque]]. These women, however, still maintained the "hourglass" shape with its relationship to fertility. During the 19th&nbsp;century, views on obesity changed in the Western world. After centuries of obesity being synonymous with wealth and social status, slimness began to be seen as the desirable standard. In his 1819 print, ''The Belle Alliance, or the Female Reformers of Blackburn!!!,'' artist [[George Cruikshank]] criticised the work of female reformers in [[Blackburn]] and used fatness as a means to portray them as unfeminine.

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==Society and culture==

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===Economic impact===

In 2005, the medical costs attributable to obesity in the US were an estimated $190.2&nbsp;billion or 20.6% of all medical expenditures, while the cost of obesity in Canada was estimated at CA$2&nbsp;billion in 1997 (2.4% of total health costs). The total annual direct cost of overweight and obesity in Australia in 2005 was A$21&nbsp;billion. Overweight and obese Australians also received A$35.6&nbsp;billion in government subsidies. The estimated range for annual expenditures on diet products is $40&nbsp;billion to $100&nbsp;billion in the US alone.

[[The Lancet]] Commission on Obesity in 2019 called for a global treaty—modelled on the [[WHO Framework Convention on Tobacco Control]]—committing countries to address obesity and undernutrition, explicitly excluding the food industry from policy development. They estimate the global cost of obesity $2&nbsp;trillion a year, about or 2.8% of world GDP.

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. Sin taxes such as a [[sugary drink tax]] have been implemented in certain countries globally to curb dietary and consumer habits, and as an effort to offset the economic tolls.

[[File:Wide Chair.jpg|thumb|left|upright=1.3|alt=An extra wide chair beside a number of normal sized chairs.|Services accommodate obese people with specialized equipment such as much wider chairs.]]

Obesity can lead to social stigmatization and disadvantages in employment. When compared to their normal weight counterparts, obese workers on average have higher rates of absenteeism from work and take more disability leave, thus increasing costs for employers and decreasing productivity. A study examining Duke University employees found that people with a BMI over 40&nbsp;kg/m² filed twice as many [[workers' compensation]] claims as those whose BMI was 18.5–24.9&nbsp;kg/m². They also had more than 12&nbsp;times as many lost work days. The most common injuries in this group were due to falls and lifting, thus affecting the lower extremities, wrists or hands, and backs. The Alabama State Employees' Insurance Board approved a controversial plan to charge obese workers $25 a month for health insurance that would otherwise be free unless they take steps to lose weight and improve their health. These measures started in January 2010 and apply to those state workers whose BMI exceeds 35&nbsp;kg/m² and who fail to make improvements in their health after one year.

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. In 2000, the extra weight of obese passengers cost airlines US$275&nbsp;million. The healthcare industry has had to invest in special facilities for handling severely obese patients, including special lifting equipment and [[bariatric ambulance]]s. Costs for restaurants are increased by litigation accusing them of causing obesity. In 2005, the US Congress discussed legislation to prevent civil lawsuits against the food industry in relation to obesity; however, it did not become law.

With the [[American Medical Association]]'s 2013 classification of obesity as a chronic disease, it is thought that health insurance companies will more likely pay for obesity treatment, counseling and surgery, and the cost of research and development of fat treatment pills or gene therapy treatments should be more affordable if insurers help to subsidize their cost. The AMA classification is not legally binding, however, so health insurers still have the right to reject coverage for a treatment or procedure.

===Size acceptance===

{{See also|Fat acceptance movement|Social stigma of obesity|Health at Every Size|Fat fetishism}}

[[File:PresidentTaftTelephoneCrop.jpg|thumb|upright=1|[[United States President]] [[William Howard Taft]] was often ridiculed for being overweight.]]

[[File:Wahlkampf_Landtagswahl_NRW_2022_-_Bündnis_90-Die_Grünen_-_Heumarkt_Köln_2022-05-13-4484.jpg|thumb|upright=1|German politician [[Ricarda Lang]] is a victim of fat shaming on the internet.]]

A number of organizations exist that promote the acceptance of obesity. They have increased in prominence in the latter half of the 20th&nbsp;century. The US-based [[National Association to Advance Fat Acceptance]] (NAAFA) was formed in 1969 and describes itself as a civil rights organization dedicated to ending size discrimination.

The [[International Size Acceptance Association]] (ISAA) is a [[non-governmental organization]] (NGO) which was founded in 1997. It has more of a global orientation and describes its mission as promoting size acceptance and helping to end weight-based discrimination. These groups often argue for the recognition of obesity as a disability under the US [[Americans With Disabilities Act]] (ADA). The American legal system, however, has decided that the potential public health costs exceed the benefits of extending this anti-discrimination law to cover obesity.

===Industry influence on research===

In 2015, the ''New York Times'' published an article on the [[Global Energy Balance Network]], a nonprofit founded in 2014 that advocated for people to focus on increasing exercise rather than reducing calorie intake to avoid obesity and to be healthy. The organization was founded with at least $1.5M in funding from the [[Coca-Cola Company]], and the company has provided $4M in research funding to the two founding scientists Gregory A. Hand and [[Steven Blair|Steven N. Blair]] since 2008.