Encyclopedia
Obesity is a condition in which the natural energy reserve, stored in the fatty tissue of
humans and mammals, is increased to a point where it is a risk factor for certain
health conditions or increased
mortality. Obesity develops from the interaction of individual
biology and the environment. Excessive body weight has been shown to correlate with various diseases, particularly cardiovascular disease, diabetes mellitus type 2,
sleep apnea, and osteoarthritis. Obesity is both an individual clinical condition and is increasingly viewed as a serious public health problem.
Definition
In the clinical setting, obesity is typically evaluated by measuring BMI , waist circumference, and evaluating the presence of risk factors and comorbidities.. It is calculated by dividing the subject's weight in kilograms by the square of his/her height in metres .
The current definitions commonly in use establish the following values, agreed in 1997 and published in 2000:
- A BMI less than 18.5 is underweight
- A BMI of 18.5 - 24.9 is normal weight
- A BMI of 25.0 - 29.9 is overweight
- A BMI of 30.0 - 39.9 is obese
- A BMI of 40.0 or higher is severely obese
BMI is a simple and widely used method for estimating body fat. In
epidemiological analyses BMI alone is used as an indicator of prevalence and incidence.
BMI as an indicator of a clinical condition is used in conjunction with other clinical assessments, such as waist circumference. In a
clinical setting, physicians take into account race, ethnicity, lean mass , age, sex, and other factors which can affect the interpretation of BMI. BMI overestimates body fat in persons who are very muscular, and it can underestimate body fat in persons who have lost body mass .
Waist circumference
BMI does not take into account differing ratios of adipose to lean tissue; nor does it distinguish between differing forms of adiposity, some of which may correlate more closely with cardiovascular risk. Increasing understanding of the biology of different forms of adipose tissue has shown that
visceral fat or
central obesity has a much stronger correlation, particularly with cardiovascular disease, than the BMI alone.
The absolute waist circumference or waist-hip ratio
Risk factors and comorbidities
The presence of risk factors and diseases associated with obesity are also used to establish a clinical diagnosis. Coronary heart disease, type 2 diabetes, and
sleep apnea are possible life-threatening risk factors that would indicate clinical treatment of obesity. found obese American subjects approximately half as wealthy as thin ones. When income differentials were factored out, the inequity persisted — thin subjects were inheriting more wealth than fat ones. Another study finds women who married into higher status are predictably thinner than women who married into lower status.
Complications
Obesity, especially central obesity , is an important risk factor for the "metabolic syndrome" , the clustering of a number of diseases and risk factors that heavily predispose for cardiovascular disease. These are
diabetes mellitus type 2, high blood pressure, high blood cholesterol, and triglyceride levels . An inflammatory state is present, which — together with the above — has been implicated in the high prevalence of
atherosclerosis , and a prothrombotic state may further worsen cardiovascular risk.
Apart from the metabolic syndrome, obesity is also
correlated with a variety of other complications. For many of these complaints, it has not been clearly established to what extent they are caused directly by obesity itself, or have some other cause that causes obesity as well. Most confidence in a direct cause is given to the mechanical complications in the following list:
- Cardiovascular: congestive heart failure, enlarged heart and its associated arrhythmias and dizziness, cor pulmonale, varicose veins, and pulmonary embolism
- Endocrine: polycystic ovarian syndrome , menstrual disorders, and infertility
- Gastrointestinal: gastroesophageal reflux disease , fatty liver disease, cholelithiasis , hernia, and colorectal cancer
- Renal and genitourinary: urinary incontinence, glomerulopathy, hypogonadism , breast cancer , uterine cancer , stillbirth
- Integument : stretch marks, acanthosis nigricans, lymphedema, cellulitis, carbuncle
A
carbuncle is an abscess [i] larger than a boil [i], usually with one or more opening ...
s, intertrigo
- Musculoskeletal: hyperuricemia , immobility, osteoarthritis, low back pain
- Neurologic: stroke, meralgia paresthetica, headache, carpal tunnel syndrome, dementia
- Respiratory: dyspnea, obstructive sleep apnea, hypoventilation syndrome, Pickwickian syndrome, asthma
- Psychological: Depression, low self esteem, body dysmorphic disorder, social stigmatization
While being severely obese has many health ramifications, those who are somewhat overweight face little increased
mortality or morbidity. Some studies suggest that the somewhat "overweight" tend to live longer than those at their "ideal" weight. This may in part be attributable to lower mortality rates in diseases where death is either caused or contributed to by significant weight loss due to the greater risk of being underweight experienced by those in the ideal category. Another factor which may confound mortality data is smoking, since obese individuals are less likely to smoke. Osteoporosis is known to occur less in slightly overweight people.
Therapy
The mainstay of treatment for obesity is an energy-limited
diet and increased
exercise. In studies, diet and exercise programs have consistently produced an average weight loss of approximately 8% of total body mass on average . While not all dieters will be satisfied with this outcome, studies have shown that a loss of as little as 5% of body mass can create enormous health benefits.
A more intractable therapeutic problem appears to be weight loss maintenance. Of dieters who manage to lose 10% or more of their body mass in studies, 80-95% will regain that weight within two to five years. It appears that the
homeostatic mechanisms regulating body weight are very robust , and vigorously defend against weight loss. Much important research is now being devoted to determining what factors can improve the currently dismal weight loss maintenance rates.
Recent scientific research has cast some doubt over whether or not dieting actually improves health, with some studies indicating that dieting may in fact be more detrimental than remaining overweight.
In a clinical practice guideline by the American College of Physicians, the following five recommendations are made:
- People with a BMI of over 30 should be counseled on diet, exercise and other relevant behavioral interventions, and set a realistic goal for weight loss.
- If these goals are not achieved, pharmacotherapy can be offered. The patient needs to be informed of the possibility of side-effects and the unavailability of long-term safety and efficacy data.
- Drug therapy may consist of sibutramine, orlistat, phentermine, diethylpropion, fluoxetine, and bupropion. For more severe cases of obesity, stronger drugs such as amphetamine and methamphetamine may be used on a selective basis. Evidence is not sufficient to recommend sertraline, topiramate, or zonisamide.
- In patients with BMI > 40 who fail to achieve their weight loss goals and who develop obesity-related complications, referral for bariatric surgery may be indicated. The patient needs to be aware of the potential complications.
- Those requiring bariatric surgery should be referred to high-volume referral centers, as the evidence suggests that surgeons who frequently perform these procedures have fewer complications.
Much research focuses on new
drugs to combat obesity, which is seen as the biggest health problem facing developed countries. Nutritionists and many doctors feel that these research funds would be better devoted to advice on good
nutrition, healthy eating, and promoting a more active lifestyle.
Medication most commonly prescribed for diet/exercise-resistant obesity is
orlistat and
sibutramine . In the presence of
diabetes mellitus, there is evidence that the anti-diabetic drug
metformin can assist in weight loss — rather than sulfonylurea derivatives and
insulin, which often lead to further weight gain. The thiazolidinediones can cause slight weight gain, but decrease the "pathologic" form of abdominal fat, and are therefore often used in obese
diabetics.
Increasingly,
bariatric surgery is being used to combat obesity. The most common weight loss surgery in
Europe and
Australia is the
adjustable gastric band where a silicone ring is placed around the top of the stomach to help restrict the amount of food eaten in a sitting. This surgery has been FDA approved in the United States since 2001 but has been being used in other parts of the world since the early 1990s. It is considered the safest and least invasive of the available weight loss surgeries such as
Roux-en-Y gastric bypass surgery , biliopancreatic diversion, and stomach stapling . Unlike those more invasive techniques the band surgery does not cut into or reroute any of the digestive tract and is completely reversible. Removing the implant returns the stomach to its pre-surgical norm. All of these surgeries can be done
laparoscopically. The more invasive of the surgeries usually bypass or remove some portion of the patient's intestines which causes malabsorption and dumping.
All of these surgeries come with risk to the patient. For instance a recent study by the U.S. Department of Health and Human Service showed a 40% complication rate within 180 days of bariatric surgery. Moreover these surgeries do not guarantee either successful weight loss or reduced morbidity and mortality. Patients are also required to to make lifelong changes to their diet if they are to keep the lost weight off in the long term. Therefore, as with any major surgery, patients needs to carefully evalute the long term ramifications of their choice.
Cultural and social significance
Etymology
Obesity is the nominal form of
obese which comes from the
Latin obesus, which means "stout, fat, or plump."
Esus is the past participle of
edere , with
ob added to it. In Classical Latin, this verb is seen only in past participial form. Its first attested usage in
English was in 1651, in Noah Biggs's
Matæotechnia Medicinæ Praxeos.
History and obesity
In several human cultures, obesity was associated with
physical attractiveness, strength, and fertility. Some of the earliest known cultural artifacts, known as
Venus figurines, are pocket-sized
statuettes representing an obese female figure. Although their cultural significance is unrecorded, their widespread use throughout pre-historic Mediterranean and
European cultures suggests a central role for the obese female form in magical rituals, and suggests cultural approval of this body form. This is most likely due to their ability to easily bear children and survive
famine.
Obesity was occasionally considered a
symbol of
wealth and social status in cultures prone to food shortages or famine. Well into the early modern period in European cultures, it often served this role. But as food security was realised, it came to serve more as a visible signifier of "lust for life", appetite, and immersion in the realm of the erotic. This was especially the case in the visual arts, such as the paintings of
Rubens , whose regular use of the full female figures gives us the description
Rubenesque for plumpness. Obesity can also be seen as a symbol within a system of prestige. "The kind of food, the quantity, and the manner in which it is served are among the important criteria of social class. In most tribal societies, even those with a highly stratified social system, everyone - royalty and the commoners - ate the same kind of food, and if there was famine everyone was hungry. With the ever increasing diversity of foods, food has become not only a matter of social status, but also a mark of one's personality and taste."
Contemporary culture
In modern Western culture, the obese body shape is widely regarded as unattractive. Obese bodies are rarely positively represented in mainstream media. Many negative stereotypes are commonly associated with obese people, such as the belief that they are lazy, dirty, stupid, or even evil. Some point to gluttony, the second of the seven deadly sins, when referring to the this last stereotype. Obese children, teenagers and adults face a heavy social stigma. Obese children are frequently the targets of bullies and are often shunned by their peers. Obesity in adulthood can lead to a slower rate of career advancement. Most obese people have experienced negative thoughts about their body image, and many take drastic steps to try to change their shape.
Not all contemporary cultures disapprove of obesity. There are many cultures which are traditionally more approving of obesity, including some African, Arabic, Indian, and Pacific Island cultures. Especially in recent decades, obesity has come to be seen more as a medical condition in modern Western culture.
Recently emerging is a small but vocal fat acceptance movement that seeks to challenge weight-based discrimination. Obesity acceptance and advocacy groups have initiated litigation to defend the rights of obese people and to prevent their social exclusion.
Popular culture
Various stereotypes of obese people have found their way into expressions of popular culture. A common stereotype is the obese character who has a warm and dependable personality, but equally common is the obese vicious bully.
Gluttony and obesity are commonly depicted together in works of fiction. In cartoons, obesity is often used to comedic effect, with fat
cartoon characters having to squeeze through narrow spaces, frequently getting stuck or even exploding.
It can be argued that depiction in popular culture adds to and maintains commonly perceived stereotypes, in turn harming self esteem of obese people. A charge of discrimination on the basis of appearance could be leveled against these depictions.
On the other hand, obesity is often associated with positive characteristics such as good
humor , and some people are more
sexually attracted to obese people than to slender people .
Public health and policy
Prevalence
;Iran
Variations in wealth result in malnutrition and obesity co-existing. According to a 1997 survey, the prevalences of moderate and severe underweight, stunting, and wasting in under-five year children were 10.9%, 15.9%, and 4.9%, respectively, while the prevalence of overweight was 4.3%. Obesity in girls in Tehran and other large cities was recorded at more than 13%..
;United Kingdom
The Health Survey for England predicts that more than 12 million adults and 1 million children will be obese by 2010 if no action is taken.
;United States
The prevalence of overweight and obesity in the United States makes obesity a leading public health problem. The United States has the highest rates of obesity in the
developed world. From 1980 to 2002, obesity has doubled in adults and overweight prevalence has tripled in children and adolescents . From 2003-2004, "children and adolescents aged 2 to 19 years, 17.1% were overweight...and 32.2% of adults aged 20 years or older were obese." This sudden rise in obesity prevalence is attributed to environmental and population factors rather than individual behavior and biology because of the rapid and continual rise in the number of overweight and obese individuals.. The current environment produces risk factors for decreased physical activity and for increased calorie consumption. These environmental factors operate on the population to decrease physical activity and increase calorie consumption.
;Venezuela
More than 21% of the population of Venezuela is obese.
Environmental factors
While it may often appear obvious why a certain individual gets fat, it is far more difficult to understand why the average weight of certain societies have recently been growing. While genetic causes are central to understanding obesity, they cannot fully explain why one culture grows fatter than another.
This is most notable in the
United States. In the years from just after the
Second World War until 1960 the average person's weight increased, but few were obese. In the two and a half decades since 1980 the growth in the rate of obesity has accelerated markedly and is increasingly becoming a public health concern.
There are a number of theories as to the cause of this change since 1980. Most believe it is a combination of various factors.
- Lack of activity: obese people appear to be less active in general than lean people, and not just because of their obesity. A controlled increase in calorie intake of lean people did not make them less active; correspondingly when obese people lost weight they did not become more active. Weight change does not affect activity levels, but the converse seems to be the case.
- One of the most important is the much lower relative cost of foodstuffs: massive changes in agricultural policy in the United States and Europe have led to food prices for consumers being lower than at any point in history. Sugar and corn syrup, two huge sources of food energy, are some of the most subsidized products by the United States government. This can raise costs for consumers in some areas but greatly lower it in others. Current debates into trade policy highlight disagreements on the effects of subsidies.
- Increased marketing has also played a role. In the early 1980s in America the Reagan administration lifted most regulations pertaining to sweets and fast food advertising to children. As a result, the number of advertisements seen by the average child increased greatly, and a large proportion of these were for fast food and sweets.
- Changes in the price of petrol are also believed to have had an effect, as unlike during the 1970s it is now affordable in the United States to drive everywhere — at a time when public transit goes underused. At the same time more areas have been built without sidewalks and parks.
- The changing workforce as each year a greater percent of the population spends their entire workday behind a desk or computer, seeing virtually no exercise. In the kitchen the microwave oven has seen sales of calorie-dense frozen convenience foods skyrocket and has encouraged more elaborate snacking.
- A social cause that is believed by many to play a role is the increasing number of two income households in which one parent no longer remains home to look after the house. This increases the number of restaurant and take-out meals.
- Urban sprawl may be a factor: obesity rates increase as urban sprawl increases, possibly due to less walking and less time for cooking.
- Since 1980 both sit-in and fast food restaurants have seen dramatic growth in terms of the number of outlets and customers served. Low food costs, and intense competition for market share, led to increased portion sizes — for example, McDonalds french fries portions rose from 200 Calories in 1960 to over 600 Calories today.
- Increased food production is a probable factor. The U.S. produces three times more food than U.S. residents eat.
- Increasing affluence itself may be a cause, or contributing factor since obesity tends to flourish as a disease of affluence in countries which are developing and becoming westernised . This is supported by a dip in American GDP after 1990, followed by a substantial increase. U.S. obesity statistics followed the same pattern, offset by two years.
- An aging population may also be a major factor, as the likelihood of becoming obese increases with age. Beyond their twenties, the older a person becomes the slower their metabolism becomes, reducing the amount of calories required to sustain the body, thus if a person does not reduce their intake of food with age, they will become obese over time. As the average age of individuals within a society increases, the rate of obesity also increases. This situation is exacerbated by the baby boom generation, which represents a disproportionately large portion of the population in many countries and is currently nearing the latter end of the typical lifespan in affluent nations, and therefore is in the high-risk zone for obesity.
Interestingly an increase in the number of Americans who
exercise and
diet occurred before the increase in obesity, and some scholars have even argued that these trends actually encouraged obesity. Nearly all diets fail, with participants resuming their previous eating habits or even engaging in binge eating. Many then see an overall increase in their weight. If the diet is then repeated and abandoned again, a pattern of rising and falling weight is established, known as weight cycling. Similarly those who work out but then stop can end up being heavier than those who never exercised.
Public health and policy responses
On top of controversies about the causes of obesity, and about its precise health implications, come
policy controversies about the correct approach to obesity. The main debate is between "personal responsibility" advocates, who resist regulatory attempts to intervene in citizen's private dietary habits, and "public interest" advocates, who promote regulations, on the same public health grounds as the restrictions applied to tobacco products. In the U.S., a recent bout in this controversy involves the so-called Cheeseburger Bill, an attempt to indemnify food industry businesses from what some consider to be frivolous lawsuits by obese clients.
"Personal responsibility" advocates work on the basis that, as the
microbiologist Rene Dubos once said, health ought not to be considered an end in itself, but "the condition best suited to reach goals that each individual formulates for himself" . Any other definition permits authorities to curtail the autonomy of the self-determining individual, imposing quantity over quality of life onto them, undermining his civil liberties. As much as principled doctors, personal responsibility arguments have also been offered by food producer lobbies. In 1961, for example, as President
John F Kennedy raised concerns about a lack of fitness in American society, a spokesman for the U.S. Dairy industry, Frank R. Neu, wrote advertorials warning
We May Be Sitting Ourselves To Death. Not food regulation, but personal exercising, is mooted as the solution.
When it comes to
childhood obesity, personal responsibility also means parental responsibility. A survey by the nonpartisan group Public Agenda found 68 percent of American parents said it was "absolutely essential" to teach their children good eating habits, but only 40 percent believe they had succeeded. Fewer parents say it is essential to teach their children about physical fitness , but more believe they have succeeded . Overall, parents said they found it difficult to protect their children from negative social messages on a range of topics, including bad nutrition.
On July 15, 2004, the
United States Department of Health and Human Services announced a new policy from HHS' Centers for Medicare & Medicaid Services removing language in the Medicare Coverage Issues Manual stating that obesity is not an illness. According to the press release "This step allows members of the public to request that Medicare review medical evidence to determine whether specific treatments related to obesity would be covered by Medicare. By law, Medicare covers specified medically necessary services for illness and injury. The prior manual language, because it stated that obesity was not an illness, could prevent Medicare from covering treatments for diseases related to obesity."
Non-medical consequences
Besides increases in disease and mortality there are other implications of the present world trend in obesity. Among these are:
- Increased pressure on airline revenues due to lobbying efforts to increase seating width on commercial airplanes and due to higher fuel costs..
- Increased litigation by obese persons suing restaurants and airlines . Note that the Personal Responsibility in Food Consumption Act of 2005 was motivated by a need to reduce litigation from obesity activists.
- Sizeable societal economic costs attributable to obesity, with medical costs attributable to obesity rising to 78.5 billion dollars or 9.1 percent of all medical expenditures in the U.S. as of 1998.
See also
References
External links
- - Obesity pages
- by a Joint WHO/FAO Expert consultation . by GreenFacts.
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