Solved: Why many people overeat?

An international team, led by Yale School of Medicine, has found that "free radicals" -- molecules tied to ageing and tissue damage -- are crucial to suppressing appetite, the 'Daily Express' reported.

In fact, in its study of brain circuits that control hunger, the researchers have found that elevating free radical levels suppressed appetite in obese mice by activating satiety promoting melanocortin neurons.

However, free radicals are also thought to drive the ageing process, they say.

Lead author Prof Tamas Horvath said: "It's a Catch-22. On one hand, you must have these critical signalling molecules to stop eating. On the other hand if exposed to them chronically, free radicals damage cells and promote ageing."

The team said the crucial role of free radicals in promoting satiety, as well as degenerative processes linked to ageing, may explain why it has been difficult to develop therapeutic strategies for obesity without major side effects.

Current studies are addressing whether satiety could be promoted without sustained elevation of free radicals in the brain and periphery.

The latest findings have been published in the 'Nature Medicine' journal.