obesity
Meaning of obesity: Major medical bodies classify obesity as a chronic disease, because the body actively defends an enlarged fat store rather than simply holding surplus weight.
Definition of obesity
Obesity is a chronic condition in which stored body fat has risen to a level that harms health and raises the likelihood of several other diseases. It is assessed mainly through body mass index, often alongside waist measurement, and it develops from an interaction of inherited biology, medicines, behavior and surroundings rather than from any single cause.
Why is it treated as a disease rather than a state?
Body weight is regulated, not merely accumulated. Fat tissue releases hormones, leptin chief among them, that report the size of the store to the brain, and the brain adjusts appetite and energy use in response. In obesity that signaling works less well, so the brain reads a large store as insufficient. When weight falls, appetite hormones shift and resting energy use drops below what the smaller body alone would predict, and both changes persist for a long time. That physiology is why weight regain after loss is so common, and it is a large part of why major medical bodies classify obesity as a chronic disease. The classification changes how the condition is recorded, funded and researched.
What contributes to it?
| Contributor | How it acts |
|---|---|
| Inherited biology | Many genes each nudge appetite, fullness and fat storage; rare single gene forms also exist |
| Medicines | Several classes, among them some antipsychotics, antidepressants, steroids and diabetes drugs, cause weight gain |
| Hormonal conditions | An underactive thyroid and Cushing syndrome are examples that alter energy balance |
| Sleep and shift work | Short or broken sleep shifts the hormones controlling hunger and fullness |
| Surroundings | Food cost and availability, marketing, and how much movement ordinary daily life requires |
What conditions travel with it?
Fat stored around the abdominal organs is metabolically active and releases inflammatory signals. Type 2 diabetes, high blood pressure, disordered blood fats, fatty liver disease and obstructive sleep apnea all become more likely, and several of them cluster together under the heading metabolic syndrome. Cardiovascular disease and a number of cancers occur at higher rates, including cancers of the uterus, kidney, liver, bowel and, after menopause, the breast. Load on the joints raises musculoskeletal problems, osteoarthritis of the knee most of all. Association is not proof of cause for every item on that list, though the link is strong and consistent for most of them.
How is severity described?
Body mass index bands divide obesity into numbered classes by degree, and those classes appear in research and in deciding who is eligible for particular treatments. They describe a measurement rather than a person's health. Two people in the same class can differ in where fat is stored, in fitness, and in whether any related condition is present, which is why staging systems that grade obesity by its actual effect on health are used alongside the index rather than in place of it.
Used in a sentence
The patient was evaluated for obesity related health conditions during the annual physical examination.
Good to know
Body mass index classifies obesity from height and weight alone, so it describes risk well across a population but does not by itself describe an individual's body composition, fat distribution or health.
Word origin
Where “obesity” comes from
From Latin obesus, meaning having eaten to excess, formed from ob- (over) and edere (to eat).