Being fat is a damaging to health as smoking

The effect is the equivalent to smoking ten cigarettes a day, according to a Swedish study.

Researchers followed 46 000 men from the age of 18 for 38 years. Being obese, or smoking ten a day, doubled the risk of premature death. The study was published in the British Medical Journal.

Being overweight, seriously underweight or smoking 10 or less raised it by 30% - and interestingly the fat non-smoker ran the same risk as the fat smoker.

Those who were underweight - with a Body Mass Index (BMI) of less than 18.5 - had no increased risk of dying early, regardless of whether they smoked or not. But the team from the Karolinska Institute in Sweden found that those who were seriously underweight - with a BMI of 17 or less - ran the same risk as those who were overweight.

They looked at 45 920 men born between 1949 and 1951 who were military conscripts. In this period as few as 3% of Swedish men were exempt from military service.

Nearly 3000 of the participants died - with the incidence of death lowest in the normal weight category.