But the 54-year-old says some- times he “forgets” to be careful and is left in pain afterwards.
The illness, which is very common especially in older people, is the inflammation or infection of balloon-like sacs (diverticula) in the large intestine, leading to abdominal pain, tenderness, and fever.
Medical experts say the most common cause is a lack of dietary fibre.
Speaking alongside fellow presenter John Torode during filming of MasterChef: The Professionals, Gregg said that he was diagnosed last year.
“At that point they can burst your intestine,” he said.
“I was almost doubled up in pain when I found out a year ago.”
Explaining how he’d just experienced another painful episode, he added: “When they’re irritated already, what you’ve got to watch is alcohol and spicy food. We were eating chilis yesterday! And before that I had a skinful of beer in Dublin – and it was already playing up.”
He said a new healthy gym regime helped him to feel fitter than he had in years and he’d taken his eye off the ball.
“I forgot, because I’d been so well. But yesterday I was ill. So now you know what it is I’ve got. I’m turning into one of those old people who has things wrong with them.”
Six years ago Gregg lost three stone after being told his cholesterol level was life-threateningly high.
In 2013 he revealed: “A doctor checked my cholesterol. At 13.5, it was sky high. He told me to do something or I was looking at a massive heart attack.”
Gregg’s fourth wife Anne-Marie, 33, is expecting a baby boy this month.
Her parents are moving in to their home in Kent to help care for the new arrival, who will be named Sid.
●MasterChef: The Professionals is on BBC Two later this year.