Being extremely obese cuts a person's lifespan more than cigarettes

It's already common knowledge that obesity can cut life short by causing strokes, but a new study quantifies the toll: the most extreme cases cut a person's lifespan more than cigarettes.

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 per cent of people, or 2.1 billion, are either obese or overweight.

"Overweight" is defined as having a body mass index, or weight in kilograms divided by the square of height in meters, of 25 to 29.9. At the low end, that is 68 kilograms for someone 1.65 meters (5 feet 5 inches) tall.

"Our findings do not support the popular notion that the increase of obesity in the United States can be attributed primarily to sustained increase over time in the average daily caloric intake of Americans," lead investigator Dr. Uri Ladabaum, an associate professor of medicine at Stanford University School of Medicine, said in a journal news release.

"Although the overall trends in obesity in the United States are well appreciated and obesity prevalence may be stabilizing, our analyses highlight troublesome trends in younger adults, in women, and in abdominal obesity prevalence, as well as persistent racial/ethnic disparities," Ladabaum added.

Pamela Powers Hannley, journal managing editor, wrote in an accompanying commentary: "If we as a country truly want to take control of our health and our health care costs, [this study] should be our clarion call. From encouraging communities to provide safe places for physical activity to ensuring ample supply of healthy food to empowering Americans to take control of their health, we must launch a concerted comprehensive effort to control obesity."

The analysis, published in the journal PLOS Medicine, is the largest-ever study of the effect of extreme obesity on mortality.