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Compelling evidence indicates that prevention of obesity reduces the risk for several types of cancer, such as colon, postmenopausal breast, uterine, esophageal, and renal cell cancers. It is estimated that 20 to 30 percent of these cancerssome of the most common cancers in the United Statesmay be related to being overweight or lack of physical activity.
During the past two decades, an extensive body of research has also begun to identify an association between obesity and worse prognosis and outcomes among some cancer patients, particularly those with breast, prostate, and colon cancer.
Percentage of adults (aged 20 and older) who are at a healthy weight, overweight, or obese.
These weight groups are defined by a measurement called body mass index (BMI). BMI is found by dividing weight (in kilograms) by height (in meters) squared. Category definitions used here are:
Note: Data from 1971–1974 and 1976–1980 are for ages 20–74, but the age difference does not appear to affect the prevalence, as seen from later survey years where data are plotted for both age groupings (20–74 and 20+). Trends are evaluated only for 1991 and forward, with data for ages 20+.
Healthy weight: Falling
Note: These trends do not indicate that individuals are moving from healthy weight to obesity. Rather, the observed trends stem from a similar number of persons moving from healthy weight to overweight and from overweight to obese. Flegal et al. (2012) have suggested a leveling off of the increase in obesity, particularly for females, but this is not indicated by the overall trend analysis conducted here.
Among adults aged 20 and older in 2009–2010:
Values do not add to 100 percent because underweight (BMI less than 18.5) is not included.
When data after 1999 are examined by gender, it appears that the increases in obesity among women have leveled off, while the prevalence for men is still rising. Among women, obesity prevalence has increased for non-Hispanic black and Mexican American women but not for non-Hispanic white women. For both women and men, the 2009–2010 estimates are not statistically different from the prevalence for 2003–2008.
Increase to 33.9 percent the proportion of adults who are at a healthy weight.
Decrease to 30.6 percent the proportion of obese adults.
Overweight and obesity are most common among black and Mexican American women. The same patterns are seen for children and teens in these groups.
Overweight children are more likely to become overweight adults and to suffer from associated illnesses and premature death. As with adults, the trend toward excess weight among children has greatly increased in recent years.
Daily physical activity, balanced with appropriate calorie intake, is one of the most effective ways to avoid weight gain. Lack of activity is believed to contribute to the increase in overweight among U.S. youth and adults.
Increased TV watching and similar sedentary activity is linked with excess weight and weight-related chronic disease.
See Physical Activity for trends in physical activity.