Obesity is a condition in which the natural energy reserve of a mammal (such as a human), which is stored in fat, is expanded far beyond usual levels to the point where it is believed to pose a health risk. Obesity in wild animals is relatively rare, but it is common in domestic animals like barrows and household pets who may be castrated, spayed, overfed and underexercised.
A person with a BMI over 25 kg/m2 is considered overweight; a BMI over 30 kg/m2 is considered obese. The American Institute for Cancer Research considers a BMI between 18.5 and 25 to be an ideal target for a healthy individual (although several sources consider a person with a BMI of less than 20 to be underweight). The BMI was created in the 19th century by the Belgian statistician Adolphe Quetelet, and remained largely intact until June 1998 when the BMI was revised downward. This had the remarkable effect of changing some people's status from "ideal" weight to "overweight" in one day!
The BMI has been subject to fundamental criticism, as it ignores fat distribution in the body (see central obesity), and the fat/muscle proportion in total body weight. This means that a very fit athete with little fat but highly developed, and therefore heavy, muscles could be classified as obese. For instance according to the BMI system Brad Pitt is overweight while Russell Crowe is obese. Many researchers therefore hold that a high "waist-hip ratio" is the best indicator of metabolic disturbance, as visceral fat is more prone to cause insulin resistance (Janssen I, et al. 2004.)
Although there is no definitive explanation for the recent epidemic of obesity, the evolutionary hypothesis comes closest to providing some understanding of this phenomenon. In times when food was scarce, the ability to take advantage of rare periods of abundance and use such abundance by storing energy efficiently was undoubtedly an evolutionary advantage. This is precisely the opposite of what is required in a sedentary society, where high-energy food is available in abundant quantities in the context of decreased exercise. Although many people may have a genetic propensity towards obesity, it is only with the reduction in physical activity and a move towards high-calorie diets of modern society that it has become widespread. Significant proportions (up to 30%) of the population in wealthy countries are now obese, and seen to be at risk of ill health (see e.g. Dr Joel Fuhrman.)
As obesity has reached epidemic proportions in some areas of the world, it has also been analyzed as a public health or population-wide problem. This view suggests that the environment itself is the cause of obesity making individual attempts to control weight difficult or impossible. Suggested environmental factors that have been noted as possible causes of the obesity epidemic include: industrilization of food production, agricultural surpluses in developed countries, intensive food marketing (especially to children), changes in the built environment (e.g. elimination of public transport, elimination of parks, elmination of pedestrian ways), and international trade policy.
Eating disorders can lead to obesity, especially binge eating disorder (BED). As the name indicates, patients with this disorder are prone to overeat, often in binges. A proposed mechanism is that the eating serves to reduce anxiety, and some parallels with substance abuse can be drawn. An important additional factor is that BED patients often lack the ability to recognize hunger and satisfaction, something that is normally learnt in childhood. Learning theory suggests that early childhood conceptions may lead to an association between food and a calm mental state.
While being greatly overweight has many health ramifications, those who are somewhat overweight face little increased mortality. In fact the somewhat overwieght tend to live longer than the those at their "ideal" weight. Being overweight is a symptom of inactivity and a poor diet, both of which have important health impacts and changing diet and exercise levels, even if one's weight remains the same, provides many health benefits.
The mainstay of treatment for obesity is an energy-limited diet and increased exercise. Although adherence to this regimen can cure obesity, a large segment of patients is unable to make the required sacrifices. There might be an additional behavioral factor at the brain level "forbidding" obesity patients from losing too much weight.
Much research focusses on new drugs to combat obesity, which is seen as the biggest health problem facing developed countries. Some nutritionists feel that these these research funds would be better devoted to advice on good nutrition, healthy eating and promoting a more active lifestyle.
Medication prescribed for diet/exercise-resistant obesity is orlistat (Xenical®, reduced intestinal fat absorption by inhibiting pancreaticlipase) and sibutramine (Reductil®, Medaria®, an anorectic).
Increasingly, surgery is being used to limit stomach capacity (and thus food intake); this can happen laparoscopically. Ileal bypass reduces the length of the intestine and hence absorbing surface, but has more complications.
A leading nutritionist (Professor Thomas Sanders, the director of the Nutrition, Food & Health Research Centre at King's College London) emphasises the need for balance between activity and consumption:
In trials, there is no evidence suggesting that reducing fat intake has an effect on obesity. As long as your expenditure equals what you eat, you won't put on weight, regardless of how high the fat content is in your diet (The Times, London, 10/3/04).
Controversy also exists as to whether the concept of "obesity" is a valid one. These critics assert that physically active people are healthier than the sedentary regardless of their body weight. The focus on weight and body mass is fed, in their view, by a diet promotion industry, drug companies, and segments of the medical profession for profit purposes, by promoting a vision that equates health with slenderness, and makes extreme slenderness of a sort that is quite difficult for most people to achieve an ideal. In The Obesity Myth, Paul Campos writes that:
. . . (F)rom the perspective of a profit-maximising medical and pharmaceutical industry, the ideal disease would be one that never killed those who suffered from it, that could not be treated effectively, and that doctors and their patients would nevertheless insist on treating anyway. Luckily for it, the American health care industry has discovered (or rather invented) just such a disease. It is called "obesity". Basically, obesity research in America is funded by the diet and drug industry - that is, the economic actors who have the most to gain from the conclusion that being fat is a disease that requires aggressive treatment. Many researchers have direct financial relationships with the companies whose products they are evaluating. [1]
The United States has one of the highest obesity rates in the world and is the first nation to have people who are both impoverished and obese.
The obesity epidemic is also increasing in Europe, Asia, and throughout the Americas: as the Indian newspaper The Tribune states:
Obesity also plagues middle eastern countries, with 35 per cent of Egyptians considered obese, a greater proportion than the population in the USA at 20 per cent. -- [1]
The spread of obesity is thought to be related to the increasing westernisation of these countries (see the China project), which brings fundamental change in eating habits and decreased levels of physical activity. There is some speculation that some food industries may be delaying attempts to limit the spread of obesity, see the ABC news article. The United states response[1] in November 2003 to the WHO draft strategy on obesity introduced the notion of food industry-sponsored initiatives. These sorts of links with vested interests are regarded with scepticism by some nutritionists[1].
