The most extreme cases of obesity cut a person’s lifespan more than cigarettes, a new study shows.
The analysis, published in the journal PLOS Medicine, is the largest-ever study of the effect of extreme obesity on mortality.
It found people who are extremely obese – with a body mass index (BMI) of 40 or higher – die 6.5 to 13.7 years earlier than peers with a healthy weight.
The study was based on data from 20 large studies of people in the United States, Sweden and Australia.
It 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.
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, by scientists at the National Cancer Institute, did not calculate whether less extreme obesity shortens life, and the researchers could not say whether the results would hold for poorer, non-Western populations.
Because extreme obesity was so rare in the past, it was not possible to calculate its effect on mortality until now.
Dr Lee Kaplan, director of the weight centre at Massachusetts General Hospital in Boston, says the new calculation is unlikely to cause people with extreme obesity to shed pounds.
“That presupposes that the main reason people don’t lose weight is lack of willpower, and I’d argue that’s not the case,” he said.
“But it could have a beneficial effect if it galvanises society to change in ways that stop promoting obesity and to develop aggressive treatments for extreme obesity.”
The study comes as rates of obesity have soared. Worldwide, nearly 30 per cent of people, or 2.1 billion, are either obese or overweight.
In the US, 36 per cent of adults are obese, according to the National Centre for Health Statistics.
In Australia 28 per cent of people are considered obese and over 60 per cent are considered overweight.
“Overweight” is defined as having a body mass index (BMI) of 25.0 to 29.9, while “obesity” means a BMI of 30 or higher
Reuters