Obesity can cut life short by causing strokes and other illnesses, but a new study quantifies the toll: The most extreme cases cut a person’s life span more than smoking cigarettes.
The analysis is the largest ever of extreme obesity’s effect on mortality. It found that people who are extremely obese (for someone of average height, carrying an extra 100 pounds or more) die 6.5 to 13.7 years earlier than peers at healthy weights.
The study, based on data from 20 large studies of people in the United States, Sweden and Australia, comes as rates of obesity have soared. Worldwide, nearly 30 percent of people, or 2.1 billion, are either obese or overweight; in the U.S., that rate is 69 percent, according to Centers for Disease Control and Prevention data from 2012.
About 36 percent of U.S. adults are obese, National Center for Health Statistics data shows. The incidence of BMIs of 40 or higher has more than quadrupled since the mid-1980s, and about one in six U.S. adults is extremely obese.
Overweight is defined as having a BMI, or weight in kilograms divided by the square of height in meters, of 25.0 to 29.9. At the low end, that is 150 pounds for someone 5 feet 5 inches tall. Obesity means a BMI of 30 or higher (180 pounds at 5 feet 5 inches tall). Extreme obesity is a BMI of 40 or higher, or 241 pounds at that height.
People with a BMI of 40 to 44.9 lost an average of 6.5 years of life. Those with a BMI of 45 to 49.9 lost 8.9 years, while BMIs of 50 to 54.9 cut 9.8 years and 55 to 59.9 cut 13.7 years. Among people with a healthy weight, those who smoked lost about 8.9 years.
The study included data on 9,564 adults with extreme obesity and 304,011 of normal weight.
The overall risk of dying at any given time rose continuously with increasing BMI within the extremely obese group, mostly due to heart disease, cancer and diabetes.
The study, by scientists at the National Cancer Institute, did not calculate whether less extreme obesity shortens life.