Scientists in Finland believe that a special formula added to food could increase the lifespan of obese people.

Researchers at the University of Helsinki found that a formula of plant sterols and mineral nutrients extended the lives of obese rats by 60% when it was added to fatty food, reported BBC News Online.

The researchers believe the formula, named MultiBene, works by reducing cholesterol and blood pressure levels.

However, lead researcher Professor Heikki Karppanen said that the lifespan increase was likely to be less in humans - perhaps around 20%.

"MultiBene could in theory be added to nearly any food and even drinks and if it was I am confident we would see a similar affect. But the problem with industrialised food is that this is probably not possible to add MultiBene when food is produced on such a mass scale. I suppose in the end people should just change their diets," Karppanen was quoted as saying.

Professor Anthony Barnett, head of the diabetes and obesity group at the University of Birmingham, UK, said studies on rats do not always have the same effects on humans.

"In reality a person will have to eat such large quantities to have any significant effect. And really there is not substitute for exercise and healthy eating.

"To get a 20% increase in life expectancy an obese person would have to lose 10kg in weight and keep it off for five years," Barnett was quoted by the BBC as saying.