OVERWEIGHT

Overweight is generally defined as having more body fat (adipose tissue) than is optimally healthy. Being overweight is a common condition, especially where food supplies are plentiful and lifestyles are sedentary. As much as 64% of the United States adult population is considered either overweight or obese, and this percentage has increased over the last four decadesA series of graphics from the Centers for Disease Control and Prevention (CDC) shows the trend in which the prevalence of obesity has increased in the U.S. during the past three decades: Obesity Epidemic: U.S. Temporal Trends 1985-2004 Excess weight has reached epidemic proportions globally, with more than 1 billion adults being either overweight or obese. Increases have been observed across all age groups.
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 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.

Health-related implications

Animals can suffer from obesity as well. This German Shepherd dog is noticeably overweight.
While the negative health outcomes associated with obesity are accepted within the medical community, the health implications of the overweight category are more controversial. The generally accepted view is that being overweight causes similar health problems as obesity just to a lesser degree. Adams et al. estimated that the risk of death increases by 20 to 40 percent among overweight persons. and the Framingham Heart Study found that being overweight at age 40yrs reduced your life expectancy by three years.Flegal et al., however, found that the mortality rate 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.
Being overweight has been identified as a cause of cancer, and is projected to overtake smoking as the primary cause of cancer in developed countries as cases of cancer linked to smoking dwindle.
Psychological well-being is also at risk in the overweight individual. Discrimination against fat persons is common socially and legally. This may affect their ability to find a mate or employment.

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 physical exercise and sedentary lifestyle
Overeating
Poor nutrition
Genetic predisposition
Hormonal imbalances (e.g. hypothyroidism)
Metabolic disorders, which could be caused by repeated attempts to lose weight by weight cycling,
Eating disorders (such as binge eating)
Alcoholism
Stress
Insufficient or poor-quality sleep
Psychotropic medication (e.g. olanzapine)
Smoking cessation and other stimulant withdrawal



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 physical exercise. For those who are obese rather than overweight, more intensive therapies such as anti-obesity drugs and/or bariatric surgery are sometimes used.
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. Moreover, for all individuals, repeatedly losing weight and then gaining it back (weight cycling or "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.
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.