Fat's the way to do it for a longer life

BEING overweight or mildly obese means you will live longer on average than people who are slim or skinny, according to the astonishing conclusion of a team of statistics experts.

A person who is overweight can expect to live two and a half months longer than someone of 'ideal' weight and 15 months longer than an underweight person, concludes the study of the relationship between body mass index (BMI) and longevity.

The research, by actuarial mathematicians at Heriot-Watt University in Edinburgh, appears to overturn the widespread assumption that the fat face an early grave. And in the age of size-zero models, it also highlights the dangers of being underweight.

The scientists confirmed a link between being overweight and increased incidence of long-term ill health, although the difference is perhaps not as dramatic as many might expect. Almost 55% of 70-year-old men of normal weight suffer high blood pressure, compared with 65% of men of the same age who are morbidly obese.

An examination of the link between smoking and life expectancy by the same team confirmed it is well worth kicking the habit at any stage.

Giving up aged 30 will buy you at least an extra five years on average, and even 70-year-olds who quit will enjoy an extra year.

The Scottish Faculty of Actuaries commissioned the new research, which included examining databases in the UK and from the world-famous Framingham Heart Study, named after a Massachusetts community whose 10,000 inhabitants share their health data in return for free medical care.

The Scottish team concluded that:

&149 A 20-year-old man who is overweight or mildly obese on the BMI scale (25-40) will live on average to 78.8 years; an underweight counterpart (less than 18.5) will live to 77.5.

• A 20-year-old woman who is overweight or mildly obese can expect to live to 82.5, while the underweight will typically die at 81.8.

• While the overweight live longer, they are more likely than lighter people to suffer from diabetes and high blood pressure. They are also more likely to get strokes and heart attacks.

• In relation to smoking, a male can add 5.7 years to his life by stopping smoking at 30, while a female who quits at the same time will gain another 5.4 years.

• If the average man holds off until he is 40 before stopping the habit, he will get another 5.1 years, compared with what would happen if he continued smoking. For women the difference at 40 is 4.7 years.

• Non-smokers can typically expect their GP to tell them that they have a potentially life-threatening illness at 73.3 for males and 78.2 for females.

&149 Smokers on average should expect bad medical news from the family doctor at 65.8 years for a man and 71.4 years for a woman.

Howard Waters, professor of actuarial mathematics at Heriot-Watt University, said: "What the study makes clear is that obesity in itself – at least as it is measured by the BMI – is not as much of an indicator of life expectancy as many other factors, such as smoking.

"It causes things such as diabetes and hypertension. These things in themselves do not actually kill, although they can contribute to other conditions that will kill, such as heart disease.

"However, it's not simple. Obesity and its effects will still need to be treated, in far more people, and the costs will be very considerable."

Dr Laurence Gruer, director of public health science with Health Scotland, said: "It's true that being very underweight is very bad for you; one reason being that it's often associated with smoking, and it tends to be an indicator of serious conditions such as anorexia. And being severely underweight can compromise the body's ability to fight infection.

"But even though many of the conditions associated with obesity are treatable, the best way to live an enjoyable life is to aim for a healthy weight. We are learning more and more about obesity and its effects, such as the link between obesity and dementia and with certain cancers. And we are even seeing patients needing ankle transplants because of the strain of the weight on their bodies."

Caroline Toshack, a former actuary turned personal trainer and director of Living Breathing Fitness, said: "This study is interesting, but it wouldn't change my advice to a client. They do need to exercise and eat sensibly, and get their weight to a healthy level.

"The data on underweight people is interesting. Underweight people might be slim, but that doesn't mean they are at all healthy. You can be underweight but it can be all fat, which does you no good at all."

One leading expert criticised the conclusions of the study. Michael Lean, professor of human nutrition at the University of Glasgow, said: "You have to be very careful in the way you use this kind of data. Many of these statistics come from an age when far fewer people were obese than they are today and they were not as overweight at so early an age as today.

"Also, the BMI has its limitations – measuring the hip-to-waist ratio is much more relevant than just weight. It's simply not the case that obesity is healthy."