Research suggests switch to rich diet can have negative effect on life expectancy

SWITCHING TO a rich diet after a restricted diet can lower life expectancy and have negative effects on health, new research by Yorkshire academics suggests.

Experts tested an existing evolutionary theory that dietary restriction – reducing a particular or total nutrient intake without causing malnutrition – triggers a survival strategy.

The theory suggests that humans and animals invest in maintaining and repairing the body in times of low food availability, to wait for when it increases again.

But the new findings from the Healthy Lifespan Institute at the University of Sheffield and Brown University in the USA, published in Science Advances, challenge the theory.

Researchers found that fruit flies fed a restricted diet and then returned to a rich diet were more likely to die and laid fewer eggs compared with flies that spent their whole life on a rich diet.

This demonstrates that, rather than waiting for food availability to increase in the future, the flies were essentially waiting to die on a restricted diet, the scientists suggest. They add that, instead of dietary restriction increasing repair and maintenance mechanisms, it could actually be an escape from the damaging effects of a rich diet.

PhD student Andrew McCracken, from the University of Sheffield, who led the study, said: “Dietary restriction is an unusual paradox which has attracted a great deal of interest within the field of ageing.

“Our results have now pointed us towards a more refined explanation of why it occurs, and have the potential to wholly shift the focus of future research.

“Our most surprising finding was that, under certain circumstances, restricted diets can also be the origin of particular types of damage to the individual.”