The term overweight is generally used to indicate that a human has more body fat than is considered useful for the optimal functioning of the body. Being overweight is a fairly common condition for many people, especially those in developed nations where food supplies are plentiful and lifestyles often do not involve a lot of activities that generate caloric expenditure. Recent studies have indicated that as much as 64% of the adult US population is overweight, and this number is increasing.^[1] A series of graphics from the CDC also describes the obesity prevalence trends in the U.S. in the past 2 decades: Obesity Epidemic: U.S. Temporal Trends 1985-2004 Overweight is part of a three-tiered rating system, along with underweight and equal weight, used by stock analysts to indicate a particular stocks attractiveness. ... This article is about modern humans. ... In biochemistry, fat is a generic term for a class of lipids. ...

A healthy body requires a minimum amount of fat for the proper functioning of the hormonal, reproductive, and immune systems, as thermal insulation, as shock absorption for sensitive areas, and as excess energy for future use. But the accumulation of too much storage fat can impair movement and flexibility, and can alter the appearance of the body. Thermal insulation on the Huygens probe The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer. ... Gasfilled Shock absorber. ...

Classification

The degree to which a person is overweight is generally described using an indication of the amount of excess body fat present. There are several common ways to measure the amount of fat present in an individual's body.(See also body fat percentage): Body fat percentage is an estimate of the fraction of the total body mass that is adipose tissue (or referred to as Fat Mass), as opposed to lean body mass (muscle, bone, organ tissue, blood, and everything else) or referred to as Fat Free Mass. ...

• Simple Weighing: The weight of the individual is measured and compared to an estimated ideal weight. This is the easiest and most common method, but by far the least accurate, as it only measures one quantity (weight) and often does not take into account many factors such as height, body type, and relative amount of muscle mass.
• Body Mass Index (BMI): This is an adaptation of simple weighing which attempts to take into account the subject's general body size by dividing the weight by the height squared (the units for BMI are kg/m², but are rarely referenced, and BMI numbers are typically written and used as unitless numbers). This provides a slightly more accurate representation than simply measuring raw weight, but still ignores many factors which can affect the results, and is generally not accurate for many individuals.
• Skinfold Calipers or "pinch test": With this method, the skin at several specific points on the body is pinched and the thickness of the resulting fold is measured. This measures the thickness of the layers of fat located under the skin, from which a general measurement of total amount of fat in the body is calculated. This method can be reasonably accurate for many people, but it does assume particular patterns for fat distribution over the body which may not apply to all individuals, and does not account for fat deposits which may not be directly under the skin. Also, as the measurement and analysis generally involves a high degree of practice and interpretation, for an accurate result it must be performed by a professional and cannot generally be done by patients themselves.
• Bioelectrical impedance analysis: This method involves passing a small electrical current through the body and measuring the body's resistance to the electrical flow. As fat and muscle conduct electricity differently, this method can provide a direct measurement of the percentage of body fat present as compared to muscle mass. In the past, this technique could only be performed reliably by trained professionals with specialized equipment, but it is now possible to buy "home kits" which allow individuals to do this themselves with a minimum of training. Despite the improved simplicity of this process over the years, however, there are a number of factors which can affect the results, including hydration and body temperature, so a fair amount of care must still be taken when applying this test to ensure that the results are in fact accurate and applicable.
• Hydrostatic Weighing: Considered one of the more accurate methods of measuring body fat, this technique involves completely submerging the subject underwater and using special equipment to measure his or her weight while submerged. This weight is then compared with "dry weight" as recorded outside the water to determine overall body density. As fat is less dense than muscle, careful application of this technique can provide a reasonably close estimate of fat content in the body. This technique does, however, require expensive specialized equipment and trained professionals to administer it properly.
• DEXA (dual energy X-ray absorptiometry): Originally developed to measure bone density, DEXA imaging has also come to be used as a precise way to determine body fat content by using the density of various body tissues to identify which portions of the body are fat. This test is generally considered to be very accurate, but requires a great deal of expensive medical equipment and trained professionals to perform.

Despite the inherent inaccuracies, the most common method for discussing this subject used by researchers and advisory institutions is body mass index (BMI) numbers. Definitions of what is considered to be overweight change from time to time and sometimes from country to country, but the current definition proposed by both the US National Institutes of Health and the World Health Organization designates anyone with a BMI of 25 kg/m² or more to be overweight. Digital kitchen scales. ... A graph of body mass index is shown above. ... A caliper is a device used in the metalworking field of mechanical engineering, to measure the distance between two symmetrically opposing sides. ... Bioelectrical impedance analysis (BIA) is a commonly used method for estimating body composition. ... Hydrostatic equilibrium occurs when compression due to gravity is balanced by a pressure gradient which creates a pressure gradient force in the opposite direction. ... Dual energy X-ray absorptiometry (DXA, previously DEXA) is a means of measuring bone mineral density (BMD). ... A graph of body mass index is shown above. ... National Institutes of Health Building 50 at NIH Clinical Center - Building 10 The National Institutes of Health (NIH) is an agency of the United States Department of Health and Human Services and is the primary agency of the United States government responsible for biomedical research. ... The World Health Organization (WHO) is a specialized agency of the United Nations (UN) that acts as a coordinating authority on international public health. ...

BMI, however, does not account for differing amounts of muscle mass, genetic factors, or many other individual variations, and thus many individuals can have BMIs less than 25 and still be considered overweight, while others may have BMIs significantly higher without falling into this category^[2]. Many of the more accurate methods mentioned above for determining body fat content can provide better indications of whether a particular individual is overweight or not. A top-down view of skeletal muscle Muscle (from Latin musculus little mouse [1]) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. ... DNA, the molecular basis for inheritance. ...

If an individual is sufficiently overweight that excess body fat could present substantial health risks, he or she is considered to be obese. It is possible for someone to be overweight without being obese (according to the NIH and WHO, a BMI between 25 and 30 is considered to be "overweight" but not "obese"). Again, the designation of "obesity" is subject to a great deal of interpretation and many individual factors, so an individual with a BMI well below 30 may be considered to be obese depending on their particular condition, while in some cases a BMI above 30 may not actually indicate obesity (although likely still does indicate being overweight). Obesity is an excess storage of fat and can affect any mammal, such as the mouse on the left. ...

Health-related implications

While the health issues associated with obesity are well accepted within the medical community, the health implications of the overweight category are more controversial. The generally accepted view has been that overweight often shares adverse risks with obesity, relative to normal weight. Adams et al. estimate that risk of death increases by 20 to 40 percent among overweight persons.^[3]

Flegal et al. found that mortality rates for individuals who are classified as overweight (BMI 25 to 30) may actually be lower than for those with an "ideal" weight (BMI 18.5 to 25)^[4]--however, this study has been widely discredited and regarded as fatally flawed by researchers from Harvard School of Public Health, Harvard Medical School, American Cancer Society, and even the CDC agency itself, which has backtracked on the findings from the Flegal report. A detailed discussion of methodological limitations of the study is available in an article from Harvard School of Public Health.

Psychological well-being is also at risk in the overweight individual. Prejudice against the overweight is one of the last legally and socially acceptable forms of discrimination. This may affect their ability to find a mate or employment. The receipt of overt remarks from childhood into old age also shape the personality of the overweight individual, either making him/her more resolute and obstinate or too willing to please others.

Causes

Being overweight is generally caused by the intake of more calories (by eating) than are expended by the body (by exercise and everyday living). Factors which may contribute to this imbalance include:

• Limited exercise and sedentary lifestyle
• Overeating
• Poor nutrition
• Genetic predisposition
• A high glycemic index diet (i.e. a diet that consists of meals that give high postprandial blood sugar) ^{[citation needed]} (see | talk page)
• Hormone imbalances (e.g. hypothyroidism)
• Metabolic disorders, which could be caused by repeated attempts to lose weight by Weight cycling,
• An eating disorder (such as binge eating disorder)
• Alcoholism
• Stress
• Insufficient sleep
• Psychotropic medications
• Smoking cessation and other stimulant withdrawal

The amount of body fat is regulated to some extent subconsciously by the brain (by controlling caloric intake through appetite and food preferences). Although the exact mechanisms by which this occurs are not entirely known, one common theory suggests that each person may possess an inherent "set point" weight which the brain attempts to maintain, and that this set point may vary for each individual depending on a variety of factors including genetic predisposition, environment, and past experience. Overeating is a behavior that, while generally not a medical problem, in some cases is a symptom of binge eating disorder or bulimia. ... DNA, the molecular basis for inheritance. ... Glycemic index (also glycaemic index, GI) is a ranking system for carbohydrates based on their effect on blood glucose levels. ... This article or section does not cite its references or sources. ... This article or section does not cite its references or sources. ... It has been suggested that Binge eating be merged into this article or section. ... Alcoholism is the consumption of, or preoccupation with, alcoholic beverages to the extent that this behavior interferes with the drinkers normal personal, family, social, or work life, and may lead to physical or mental harm. ... In medical terms, stress is the disruption of homeostasis through physical or psychological stimuli. ... For other uses, see Sleep (disambiguation). ... A No Smoking sign Smoking cessation (commonly known as quitting, or kicking the habit) is the effort to stop smoking tobacco products. ... Stimulants are drugs that temporarily increase alertness and wakefulness. ...

This leads to the conclusion that some individuals may be predisposed to naturally maintaining different body weights than others, and thus it may be easier for some people to avoid being overweight, while others may find it much more difficult. It also suggests, however, that an individual's set point may be changeable with appropriate environment and conditioning.

Treatment

A large number of people undergo some form of treatment to attempt to reduce their weight, usually either in an attempt to improve their health, to improve their lifestyle, or for cosmetic reasons. The generally recommended treatment for being overweight is a modified or controlled diet in conjunction with increased exercise. For those who are obese rather than overweight, more intensive therapies such as drugs or surgery are sometimes used (see Obesity). Measuring body weight on a scale Dieting is the practice of ingesting food in a regulated fashion to achieve a particular objective. ... The term Exercise can refer to: Physical exercise such as running or strength training Exercise (options), the financial term for enacting and terminating a contract Category: ...

Studies suggest that reducing calorie intake by itself (dieting) may have short-term effects but does not lead to long-term weight loss, and can often result in gaining back all of the lost weight and more in the longer term. For this reason, it is generally recommended that weight-loss diets not be attempted on their own but instead in combination with increased exercise and long-term planning and weight management.

The health benefits of weight loss are also somewhat unclear. While it is generally accepted that for significantly obese patients, losing weight can reduce health risks and improve quality of life, there is some evidence to suggest that for merely overweight patients, the health effects of attempting to lose weight may actually be more detrimental than simply remaining overweight^[5]. Moreover, for all individuals, repeatedly losing weight and then gaining it back ("yo-yo dieting"), is believed to do more harm than good and can be the cause of significant additional health problems. This is caused by the loss of more muscle than fat. This article or section does not cite its references or sources. ...

There is no healthy, short-term solution for solving obesity, or being overweight. Changes in lifestyle, such as more exercise or dieting, must be permanent changes.

See also

• BBW
• Body image
• Obesity
• Underweight

Rubens Venus at the Mirror BBW, an initialism for Big Beautiful Woman, denotes an attractive, self-confident woman of size. BBWs are also the focus of a subculture with interests centered on the acceptance, support, and admiration of obese women. ... Body image is a persons perception of his or her own physical appearance. ... This article or section is in need of attention from an expert on the subject. ...

References

JAMA, published continuously since in 1883, is an international peer-reviewed general medical journal published 48 times per year. ... The New England Journal of Medicine (NEJM) is a peer-reviewed medical journal published by the Massachusetts Medical Society. ... JAMA, published continuously since in 1883, is an international peer-reviewed general medical journal published 48 times per year. ... The Public Library of Science (PLoS) is a nonprofit open access scientific publishing project aimed at creating a library of scientific journals and other scientific literature under an open content license. ...

External links

• Obesity Epidemic: U.S. Temporal Trends 1985-2004
• Ranking of Most Overweight Countries in the World 2005
• World Health Organization fact sheet on obesity and overweight