Being overweight or underweight could reduce someone’s life expectancy by four years, a study has found.
The report, published in the Lancet Diabetes and Endocrinology, involved nearly two million people who were registered with doctors in the UK.
Researchers found that from the age of 40, people at the higher end of the healthy body mass index (BMI) range – between 18.5 and 25 – had the lowest risk of dying from disease.
Those at the top and bottom ends of the BMI range risked having shorter lives.
Life expectancy for obese men and women was 4.2 and 3.5 years shorter, respectively, than people in the entire healthy BMI weight range.
The difference for underweight men and women was 4.3 years for men and 4.5 years for women.
BMI was associated with cancer, cardiovascular diseases and respiratory diseases.
However, report author Dr Krishnan Bhaskaran said not everybody in the healthy category is at the lowest risk of disease.
“For most causes of death we found that there was an ‘optimal’ BMI level, with risk of death increasing both below and above that level,” he told the BBC. “At BMIs below 21, we observed more deaths from most causes, compared with the optimum BMI levels. However, this might partly reflect the fact that low body weight can be a marker of underlying ill-health.”
Dr Katarina Kos, senior lecturer in Diabetes and Obesity at the University of Exeter, added that overweight people who could lower their BMI may reap the health benefits.
“We know from the diabetes remission data how low-calorie diets and weight loss can improve diabetes, for example,” she said. “And we know weight loss can also help in improving risk so that would also then improve mortality rates.”