Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have a negative effect on health. Obesity is most commonly caused by a combination of excessive food intakelack of physical activity, and genetic susceptibility. Obesity is mostly preventable through a combination of social changes and personal choices.
Obesity is a leading preventable cause of death worldwide, with increasing rates in adults and children.
Obesity is a medical condition in which excess body fat has accumulated to the extent Obese fat overweight chubby it may have an adverse effect on health. BMI is usually expressed in kilograms of weight per metre squared of height.
The most commonly used definitions, established by the World Health Organization WHO in and published inprovide the values listed in the table. Some modifications to the WHO definitions have been made by particular organizations.
Excessive body weight is associated with various diseases and conditionsparticularly cardiovascular diseasesdiabetes mellitus type 2obstructive sleep apneacertain types of cancerosteoarthritis and asthma. Obesity is one of the leading preventable causes of death worldwide.
Obesity increases the risk of many physical and mental conditions. These comorbidities are most commonly shown in metabolic syndrome a combination of disorders which includes: Complications are either directly caused by obesity or indirectly related through mechanisms sharing a common cause such as a poor diet or a sedentary lifestyle.
The strength of the link between obesity and specific conditions varies. One of the strongest is the link with type 2 diabetes.
Health consequences fall into two broad categories: Increased fat also creates a proinflammatory state  and a prothrombotic state. Although the negative health consequences of obesity in the general population are well supported by the available evidence, health outcomes in certain subgroups seem to be improved at an increased BMI, a phenomenon known as the obesity survival paradox.
In people with heart failure, those with a BMI between This has been attributed to the fact that people often lose weight as they become Obese fat overweight chubby more ill. People with class I obesity and heart disease do not have greater rates of further heart problems than people of normal weight who also have heart disease. In people with greater degrees of obesity, however, the Obese fat overweight chubby of further cardiovascular events is increased. At an individual level, a combination of excessive food energy intake and a lack of physical activity is thought to explain most cases of obesity.
A review identified ten other possible contributors to the recent increase of obesity: A review supported excess food as the primary factor. It has also changed significantly over time. The widespread availability of nutritional guidelines  has done little to address the problems of overeating and poor dietary choice. Most of this extra food energy Obese fat overweight chubby from an increase in carbohydrate consumption rather than fat consumption.
As societies become increasingly reliant on energy-densebig-portions, and fast-food meals, the association between fast-food consumption and obesity becomes more concerning. Agricultural policy and techniques in the United States and Europe have led to lower food prices.
In the United States, subsidization of corn, soy, wheat, and rice through the U. Obese people consistently under-report their food consumption as compared to people of normal weight. A sedentary lifestyle plays a significant role in obesity.
The World Health Organization indicates people worldwide are taking up less active recreational pursuits, while a study from Finland  found an increase and a study from the United States found leisure-time physical activity has not changed significantly. In both children and adults, there is an association between television viewing time and the risk of obesity. Like many other medical conditions, obesity is the result of an interplay between genetic and environmental factors.
As ofmore than 41 of these sites on the human genome have been Obese fat overweight chubby to the development of obesity when a favorable environment is present. The term "non-syndromic obesity" is sometimes used to exclude these conditions.
The thrifty gene hypothesis postulates that, due to dietary scarcity during human evolution, people are prone to obesity. Their ability to take advantage of rare periods of abundance by storing energy as fat would be advantageous during times of varying food availability, and individuals with greater adipose reserves would be more likely to survive famine. This tendency to store fat, however, would be maladaptive in societies with stable food supplies.
Certain physical and mental illnesses and the pharmaceutical substances used to treat them can increase risk of obesity. Medical illnesses that increase obesity risk include several rare genetic syndromes listed above as well as some congenital or acquired conditions: Certain medications may cause weight gain or changes in body composition ; these include insulinsulfonylureasthiazolidinediones Obese fat overweight chubby, atypical Obese fat overweight chubbyantidepressantssteroidscertain anticonvulsants phenytoin and valproatepizotifenand some forms of hormonal contraception.
While genetic influences are important to understanding obesity, they cannot explain the current dramatic increase seen within specific countries or globally. There are a number of theories as to the cause but most believe it is a combination of various factors.
The correlation between social class and BMI varies globally. A review in found that in developed countries women of a high social class were less likely to be obese. No significant differences were seen among men of different social classes. In the developing world, women, men, and children from high social classes had greater rates of obesity.
The decrease in strength of correlation was felt to be due to the effects of globalization.
A relationship is seen among US states: Many explanations have been put forth for associations between BMI and social class. It is thought that in developed countries, the wealthy are able to afford more nutritious food, they are under greater social pressure to remain slim, and have more opportunities along with greater expectations for physical fitness. In undeveloped countries the ability to afford food, high energy expenditure with physical labor, and cultural values favoring a larger body size are believed to contribute to the observed patterns.
A correlation in BMI changes over time has been found among friends, siblings, and spouses. Smoking has a
Obese fat overweight chubby effect on an individual's weight. Those who quit smoking gain an average of 4. In the United States the number of children a person has is related to their risk of obesity. In the developing world urbanization is playing a role in increasing rate of obesity. Malnutrition in early life is believed to play a role in the rising rates of obesity in the developing world.
Consistent with cognitive epidemiological data, numerous studies confirm that obesity is associated with cognitive deficits. The study of the effect of infectious agents on metabolism is still in its early stages. Gut flora has been shown to differ between lean and obese humans.