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.
Definition of obesity
Obesity is a concept that is being continually redefined. In humans, the
current measurement of obesity is the body mass index (BMI).
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.)
Causes and effects of obesity
- Obesity is generally a result of a combination of factors:
- Genetic predisposition
- Energy-rich diet
- Limited exercise
- Underlying illness
- An eating disorder such as binge eating disorder
- Stressful mentality (debated)
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.)
Binge Eating Disorder are people who eat too much, often in binges. The
reason they eat too much is that eating reduces anxiety. One can compare
with substance abuse, the causes are very similar. An important
additional factor is that the person lacks ability to recognize hunger
and satisfaction. The ability to recognize hunger and satisfaction is
something you learn as a child. If parents give their child food when
the child is distressed because of other factors than hunger, then the
children will associate hunger with other distresses also as an adult.
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- Obesity is correlated (in population studies) with an increased risk of:
- Heart disease
- Metabolic syndrome X
- high blood pressure
- diabetes mellitus (type II)
- high blood cholesterol and triglyceride (combined hyperlipidemia)
- Certain types of cancer
- Gastroesophageal Reflux Disease (GERD)
- obstructive sleep apnea syndrome
- Carpal tunnel syndrome
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
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
Medication prescribed for diet/exercise-resistant obesity is orlistat (Xenical?,
reduced intestinal fat absorption by inhibiting pancreatic lipase) and
sibutramine (Reductil?, Medaria?, an anorectic).
In the presence of diabetes mellitus, there is evidence that the
anti-diabetic drug metformin (Glucophage?) can assist in weight loss -
rather than sulfonylurea derivatives and insulin, which often lead to
further weight gain. The thiazolidinediones (rosiglitazone or
pioglitazone) can cause slight weight gain, but decrease the
"pathologic" form of abdominal fat, and are therefore often used in
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
Worldwide distribution of obesity
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.
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