Washington: A study of 33,000 adults has discovered that putting on a few pounds could actually lengthen your life. According to research published in the American Journal of Public Health most adults may be healthy with an extra half stone than that recommended under the current Body Mass Index(BMI) measuring system.

BMI is calculated by dividing a patient’s weight in kilograms by their height in metres squared. A rating below 18 is regarded as underweight, while above 25 is overweight and a mass index over 30 is regarded as obese.

But while many doctors use the index as a general guideline to good health, the US researchers have found that the average person classified as overweight in the UK actually lives longer.

Changing the current recommended BMI to 26 for men would allow the average male to carry 24lb more than is currently recommended. Women could quite happily tip the scales at half a stone more than suggested.

The study also found that adults with BMIs as high as 35 have the same life expectancy as skinny people who have BMIs of 20.

According to the research, only those with BMIs over 35, equivalent to 17st 6lb for a 5ft 10in man and 15st for a 5ft 5in women, face a marked reduction in life expectancy.

Researcher Dr Jerome Gronniger, of the US Congressional Budget Office, said: ‘This work does not support the idea that reducing weight alone would result in any large mortality risk reduction for most of the population.’