(NaturalNews) Severe obesity shortens a person's expected lifespan by 10 years, comparable to the effect of a lifetime spent smoking, according to a study conducted by researchers from Oxford University's Clinical Trial Service Unit and published in the journal The Lancet.
"This is the latest and most convincing demonstration of the close relationship between being overweight and poor heart health, and confirms that smoking is harmful regardless of your weight," said Peter Weissberg of the British Heart Foundation.
Researchers compared lifestyle and mortality data for nearly one million people worldwide, and found that every increase in body mass index (BMI) over 25 significantly decreased life expectancy.
BMI is a commonly used measure of obesity, calculated by dividing a person's weight in kilograms by the square of their height in meters. A range of 20-25 is considered normal, 25-30 is considered overweight, 30-40 is considered obese, and 40-50 is considered severely obese.
In the current study, moderate obesity reduced life expectancy by an average of three years, while severe obesity reduced it by 10.
"Excess weight shortens human lifespan," concluded lead researcher Gary Whitlock.
Health experts warn that it is easier to avoid gaining extra weight than it is to lose it later on.
"Being obese not only shortens life, it also leads to chronic ill-health -- diabetes, high blood pressure, gallstones, back and joint troubles," said Alan Maryon-Davis, president of the U.K. Faculty of Public Health. "My advice is don't let it creep up on you. Cut down the fat in your food and use every opportunity to be more physical."
The researchers estimated that excess weight is responsible for up to one in 16 cancer deaths and one in four deaths from heart attack or stroke among middle-aged residents of the United Kingdom. Approximately 2 percent of U.K. residents are categorized as severely obese.