For Asians, overweight is a BMI between 23 and 29.9 and obesity for all groups is a BMI of 30 or more. BMI, however, does not account extremes of muscle mass, some rare genetic factors, the very young, and a few other individual variations. Thus it is possible for an individuals with a BMI of less than 25 to have excess body fat, while others may have a BMI that is significantly higher without falling into this category. Some of the above methods for determining body fat are more accurate than BMI but are less convenient to measure. If an individual is overweight and has excess body fat it can create or lead to health risks. Reports are surfacing, however, that being mildly overweight to slightly obese – BMI being between 24 and 31.9 – may be actually beneficial and that people with a BMI between 24 and 31.9 could actually live longer than normal weight or underweight persons. Health effects
While some negative health outcomes associated with obesity are accepted within the medical community, the health implications of the overweight category are more controversial. A 2016 review estimated that the risk of death increases by seven percent among overweight people with a BMI of 25 to 27.5 and 20 percent among overweight people with a BMI of 27.5 to 30.
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.