The rates of American adults with obesity have continued to increase over the past decade according to researchers from the Centers for Disease Control and Prevention (CDC). In the years between 2007-2008 and 2015-2016, the report says the rates of obesity rose significantly among adults, from 33.7% to 39.6%. Rates of severe obesity increased during this time from 5.7% to 7.7%. The report was published online March 23, 2018 as a research letter in the Journal of the American Medical Association.
The report defines obesity as having a body mass index (BMI) of 30 or greater and defines severe obesity as having a BMI of 40 or greater. For example, an adult who is 5’ 9” tall and weighs 203 pounds has a BMI of 30. An adult who is 5’ 9” tall and weighs 271 pounds has a BMI of 40. A healthy weight for this height, according to the CDC, is between 125 and 168 pounds.
The report shows an overall trend toward a slight increase in obesity rates among youth ages 2 to 19, but this increase is not steep enough to be statistically significant. Rates of obesity among youth rose from 16.8% during 2007-2008 to 18.5% during 2015-2016. For youth, the researchers defined obesity as a BMI in the 95th percentile or above. They defined severe obesity as a BMI of at least 120% of the 95th percentile. BMI is calculated differently for children than it is for adults. For example, a 10-year-old boy of average height (4’ 8”) who weighs 102 pounds would fall into the 95th percentile for BMI, and would fit the definition for obesity.
The researchers made their calculations using data from 27,449 adults and 16,875 youth enrolled in the National Health and Nutrition Examination Survey.
Obesity and cancer
People with obesity are at higher risk than people of healthy weight to develop many serious diseases and health conditions, including heart disease, stroke, type 2 diabetes, and certain cancers.
Being overweight is clearly linked with cancers of the breast (in women past menopause), colon and rectum, endometrium, esophagus, kidney, and pancreas. There is also evidence that excess weight may contribute to cancers of the gallbladder, liver, cervix, and ovary, as well as non-Hodgkin lymphoma, multiple myeloma, and aggressive forms of prostate cancer. Excess body weight is thought to be responsible for about 8% of all cancers in the United States, as well as about 7% of all cancer deaths.
If you are overweight, consider making some lifestyle changes. Studies show that even a small weight loss – 10% of your current weight – lowers the risk of several diseases.
The American Cancer Society recommends that people try to get to and stay at a healthy weight throughout life by eating a healthy diet and getting enough physical activity. A healthy diet includes lots of vegetables and fruits, whole grains, beans, and lower calorie beverages while limiting high-calorie foods, between-meal snacks, and added sugars.
The American Cancer Society also recommends that adults get at least 150 minutes of moderate intensity or 75 minutes of vigorous intensity activity each week (or a combination of these), preferably spread throughout the week. Children and teens should get at least 1 hour of moderate or vigorous intensity activity each day, with vigorous activity on at least 3 days each week. Moderate activity is about the level of a brisk walk, while vigorous activity increases your breathing and heart rate, and makes you sweat.
It's also important to limit the amount of time during the day you spend sitting or lying down. Long hours of sedentary behavior have been linked to diabetes, heart disease, some types of cancer, and shorter life.
American Cancer Society research
The American Cancer Society (ACS) is currently funding almost $12 million worth of grants for obesity-related research in labs at research centers across the US. The studies are wide ranging, including how chemical processes in the body lead to obesity, the impact of obesity on cancer risk, progression, and survival, and ways to encourage lifestyle behaviors known to reduce obesity in adults and children.
In addition, ACS researchers are conducting their own studies about excess body weight and the links to cancer. Many of these studies rely on data from the Cancer Prevention Study II, a study of approximately 1.2 million American men and women which began in 1982. ACS researchers also collaborate on other studies here in the US and around the globe to find out more about the factors that lead to excess weight gain and which cancer types are linked to excess weight.