In an interview with The Daily Mirror newspaper, the television presenter, who's spoken openly about his Christian faith, also said he admired many older actresses who hadn't had cosmetic work done, and that "beauty comes from within".
Queen Elizabeth II reportedly thanked the 66-year-old for "giving a lot of ladies a lot of pleasure" when she gave him his MBE in 2000.
Speaking about his body, he said: "I'd rather leave the way I'm going to age in the hands of God rather than have someone inject me with some kind of fungoid or bacterium.
"It's not that my body is a temple - it's more like a shed - but I do think people should just wait and see what's going to happen.
"I look at all these old actresses who haven't had any work... and I think they look beautiful. Beauty comes from within. It's not about tautness of skin. I want my face to move and for my wife to know what kind of mood I'm in when I come home from work."
In the interview, Alan Titchmarsh also stated his position on assisted dying. He said: "It's an extraordinarily thorny issue, but I do believe in the sanctity of life.
"Whilst I am hugely sympathetic to pain, I do have a problem with assisted dying.
"I would certainly look at palliative care first. It is not something I would want to make a pronouncement on but do I think life is sacred."