Obesity may shorten a person's life expectancy by up to eight years and deprive them of almost two decades of healthy life, a new study has found.

According to Canadian scientists, obesity-related type 2 diabetes and cardiovascular disease are to blame.

They created a disease-stimulation model to estimate the risk of developing diabetes and cardiovascular disease in adults of different weights. They then assessed the role weight played in relation to years of life lost in adults aged between 20 and 79.

"Our computer modelling study shows that obesity is associated with an increased risk of developing cardiovascular disease (including heart disease and stroke) and diabetes that will, on average, dramatically reduce an individual's life expectancy and the healthy life years free from living with these chronic illnesses compared with people of normal weight," explained the study's lead author, Dr Steven Grover, of McGill University and McGill University Health Centre in Montreal.

The scientists found that people who were overweight, i.e. with a body mass index (BMI) of 25 to 29.9, were estimated to lose up to three years of life expectancy, depending on their gender and age.

Obese people with a BMI of 30-34.9 lost up to six years of life expectancy, while very obese people with a BMI of 35 or more, lost up to eight years.

This effect was greatest among younger people.

However, the scientists emphasised that excess weight does not just reduce life expectancy. It also reduces healthy life years, which they defined as years free of obesity-related diabetes and cardiovascular disease.

The study found that people who are overweight or obese lose up to four times as many healthy life years as people of a normal weight. The highest loss in healthy life years was found in young adults aged between 20 and 29 who were very obese. They lost up to 19 healthy life years.

"The pattern is clear. 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," Dr Grover commented.

He added that these calculations will hopefully help obese people and their doctors ‘to better appreciate the scale of the problem and the substantial benefits of a healthier lifestyle, including changes to diet and regular physical activity'.

Details of these findings are published in the journal, The Lancet Diabetes & Endocrinology.

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