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Extreme Obesity May Shorten Life Expectancy Up To 14 Years

Posted:  Thursday, July 10, 2014

Scientist have warned that young people who are obese could be storing up for ill health as well as shortening their lives by 14 years. Deadly impact of a poor diet and lack of exercise has been quantified for the first time in the hope it will push people into losing weight.

Adults with extreme obesity have increased risks of dying at a young age from cancer and many other causes including heart disease, stroke, diabetes, and kidney and liver diseases, according to results of an analysis of data pooled from 20 large studies of people from three countries. The study, led by researchers from the National Cancer Institute, part of the National Institutes of Health, found that people with class extreme obesity had a dramatic reduction in life expectancy compared with people of normal weight.

"While once a relatively uncommon condition, the prevalence of class III, or extreme, obesity is on the rise. In the United States, for example, six percent of adults are now classified as extremely obese, which, for a person of average height, is more than 100 pounds over the recommended range for normal weight," said Cari Kitahara, Ph.D., Division of Cancer Epidemiology and Genetics, NCI, and lead author of the study. "Prior to our study, little had been known about the risk of premature death associated with extreme obesity."

In the study, researchers classified participants according to their body mass index (BMI), which is a measure of total body fat and is calculated by dividing a person's weight in kilograms by their height in meters squared. BMI classifications (kilogram/meter-squared) are:

• Normal weight: 18.5-24.9

• Overweight: 25.0- 29.9

• Class I obesity: 30.0-34.9

• Class II obesity: 35.0-39.9

• Class III obesity: 40.0 or higher

The more an individual weighs and the younger their age, the greater the effect on their health, as they have many years ahead of them during which the increased health risks associated with obesity can negatively impact their lives.

They found that overweight individuals (BMI 25 to < 30 kg/m2) were estimated to lose up to three years of life, depending on their age and gender.

For obese individuals (30 to < 35 kg/m2) the years lost were between 1 and six years and the very obese (35 kg/m2 or more) were estimated to lose up to eight years. Young people, between 20 and 39 were worst affected.

BMI is calculated by dividing weight in kilograms, by height in metres, then dividing by height again.

The accuracy of the study findings is limited by the use of mostly self-reported height and weight measurements and by the use of BMI as the sole measure of obesity. Nevertheless, the researchers noted, the results highlight the need to develop more effective interventions to combat the growing public health problem of extreme obesity.

"Given our findings, it appears that class III obesity is increasing and may soon emerge as a major cause of early death in this and other countries worldwide," said Patricia Hartge, Sc.D., Division of Cancer Epidemiology and Genetics, and senior author of the study.