By Seamus Duff Gregg Wallace says he is trying to achieve the physique of a man four decades younger than he is – but admits he has suffered in the process. In recent years, the 57-year-old father-of-three has astonished fans by dropping five stone and going from a portly TV cooking show judge to a muscular fitness fanatic. But it seems Gregg cannot get enough of getting in shape – and has vowed to get himself into the shop of a man in his 20s. Gregg has often discussed the secrets to his incredible body transformation – explaining that he strikes a balance of exercising hard and eating health…