Katherine Flegal et al., however, found that the mortality rate for individuals who are classified as overweight (BMI 25 to 29.9) may actually be lower than for those with an "ideal" weight (BMI 18.5 to 24.9), noting that many studies show that the lowest mortality rate is at a BMI close to 25. The specific conclusions appear to depend on what other factors are controlled for, and Flegal has accordingly alleged that the findings from the 2016 review are driven by bias toward preconceived opinions.Being overweight has been identified as a risk factor for cancer, and Walter Willett predicts that being overweight will overtake smoking as the primary cause of cancer in developed countries as cases of smoking-related cancer dwindle. Being overweight also increases the risk of oligospermia and azoospermia in men.Psychological well-being is also at risk in the overweight individual due to social discrimination. Being overweight has been shown not to increase mortality in older people: in a study of 70 to 75-year old Australians, mortality was lowest for "overweight" individuals (BMI 25 to 29.9), while a study of Koreans found that, among those initially aged 65 or more, an increase in BMI to above 25 was not associated with increased risk of death. Causes
Being overweight is generally caused by the intake of more calories (by eating) than are expended by the body (by exercise and everyday activity). Factors that may contribute to this imbalance include:

Alcoholism
Eating disorders (such as binge eating)
Genetic predisposition
Hormonal imbalances (e.g.
The units therefore are kg/m2 but BMI measures are typically used and written without units.BMI provides a significantly more accurate representation of body fat content than simply measuring a persons weight. It is only moderately correlated with both body fat percentage and body fat mass (R2 of 0.68). It does not take into account certain factors such as pregnancy or bodybuilding; however, the BMI is an accurate reflection of fat percentage in the majority of the adult population.Body volume indexThe body volume index (BVI) was devised in 2000 as a computer, rather than manual, measurement of the human body for obesity and an alternative to the BMIBVI uses 3D software to create an accurate image of a person so BVI can differentiate between people with the same BMI rating, but who have a different shape and different weight distribution. BVI measures where a persons weight and the fat are located on the body, rather than total weight or total fat content and places emphasis on the weight carried around the abdomen, commonly known as central obesity. There has been an acceptance in recent years that abdominal fat and weight around the abdomen constitute a greater health risk.Simple weighingA persons weight is measured and compared to an estimated ideal weight.