Obesity

Obesity is a condition in which excess body fat has accumulated to such an extent that health may be negatively affected.It is commonly defined as a body mass index (BMI = weight divided by height squared) of 30 kg/m2 or higher.[1] This distinguishes it from being overweight as defined by a BMI of between 25-29.9 kg/m2.

Excessive body weight is associated with various diseases, particularly cardiovascular diseases, diabetes mellitus type 2, obstructive sleep apnea, certain types of cancer, and osteoarthritis. As a result, obesity has been found to reduce life expectancy. The primary treatment for obesity is dieting and physical exercise. If this fails, anti-obesity drugs and (in severe cases) bariatric surgery can be tried.

Obesity arises from too much energy intake compared with a person's basal metabolic rate and level of physical exercise. Excessive caloric intake and a lack of physical activity in genetically susceptible individuals is thought to explain most cases of obesity, with purely genetic, medical, or psychiatric illness contributing to only a limited number of cases. With rates of adult and childhood obesity increasing, authorities view it as a serious public health problem.

Although obesity is currently associated with stigmatization in the Western world, it has been perceived as a symbol of wealth and fertility at other times in history.

Causes
Most researchers agree that a combination of excessive calorie consumption and a sedentary lifestyle are the primary causes of obesity.[40] In a minority of cases, increased food consumption can be attributed to genetic, medical, or psychiatric illness. Generally however the rising prevalence of obesity is attributed to the availability of an easily accessible and palatable diet,[41] car culture and mechanized manufacturing. A 2006 review identifies ten other possible contributors to the recent increase of obesity:

(1) insufficient sleep
(2) endocrine disruptors - food substances that interfere with lipid metabolism
(3) decreased variability in ambient temperature
(4) decreased rates of smoking as smoking suppresses appetite
(5) increased use of medication that leads to weight gain
(6) increased distribution of ethnic and age groups that tend to be heavier
(7) pregnancy at a later age, (8) intrauterine and intergenerational effects
(9) positive natural selection of people with a higher BMI
(10) assortative mating, heavier people tending to form relationships with each other.

Treatment

Weight loss drugs
The first described attempts at producing weight loss are those of Soranus of Ephesus, a Greek physician, in the second century AD. He prescribed elixirs of laxatives and purgatives, as well as heat, massage, and exercise. This remained the mainstay of treatment for well over a thousand years. It was not until the 1920s and 1930s that new treatments began to appear. Based on its effectiveness for hypothyroidism, thyroid hormone became a popular treatment for obesity in otherwise healthy people. It had a modest effect but produced the symptoms of hyperthyroidism as a side effect, such as palpitations and difficulty sleeping. Dinitrophenol (DNP) was introduced in 1933; this worked by uncoupling the biological process of oxidative phosphorylation in mitochondria, causing them to produce heat instead of ATP. The most significant side-effect was a dramatic rise in body temperature, frequently causing death. By the end of the 1930s DNP had fallen out of use.

Amphetamines (marketed as Benzedrine) became popular for weight loss during the late 1930s. They worked primarily by suppressing appetite and had other beneficial effects such as increased alertness. Use of amphetamines increased over the subsequent decades, culminating in the "rainbow pill" regime. This was a combination of multiple pills, all thought to help with weight loss, taken throughout the day. Typical regimens included stimulants, such as amphetamines and thyroid hormone, diuretics, digitalis, laxatives, and often a barbiturate to suppress the side effects of the stimulants. In 1967/1968 a number of deaths attributed to diet pills triggered a Senate investigation and the gradual implementation of greater restrictions on the market. This culminating in 1979 with the FDA banning the use of amphetamines, then the most effective of the diet drugs, in diet pills.

Meanwhile, phentermine had been FDA approved in 1959 and fenfluramine in 1973. The two were no more popular then other drugs until in 1992 a researcher reported that the two caused a 10% weight loss which was maintained for over two years. Fen-phen was born and rapidly became the most commonly prescribed diet medication. Dexfenfluramine (Redux) was developed in the mid-1990s as an alternative to fenfluramine with less side-effects, and received regulatory approval in 1996.