The 52-year-old, Bolton-born comedian and TV presenter shared before and after photos on Instagram after completing the 75 Hard Challenge, a 75-day fitness programme.
In the photos, Paddy looked noticeably slimmer and more toned, prompting some followers to question whether the images had been digitally altered.
Speaking on BBC Radio 2’s The Scott Mills Breakfast Show, he said: “The most hilarious thing was people saying my before photo was AI.
“Surely it’s the after which you AI?
“The AI is when you’re painting on abs.”
He explained that boredom was the main reason he started the challenge.
The 75 Hard Challenge, created by US entrepreneur Andy Frisella, includes two 45-minute workouts each day (one of which must be outdoors), drinking 4.5 litres of water daily, following a diet, not consuming alcohol, and reading 10 pages of a non-fiction book.
Paddy said he took the ‘before’ photo after a period of indulgence.
He said: “I thought ‘right, I’m going to eat what I want and not do anything’, I wanted to go ground zero and work my way up again.
“That was my idea about it when I took that picture.
“I look back at it, I was like ‘my god, I have gone for it there’.”
In his Instagram post to 2.2 million followers, he admitted being surprised at how much weight he had gained.
Paddy said: “I still can’t believe how much I’d let myself go.
“That before pic is the result of just under two months of binge eating – beer, cakes, and biscuits.
“The effect it had on my body, and more importantly my mind, was staggering.”
He plans to share a full 75-day picture time-lapse next week.
He said: “It really is amazing what can be achieved in such a short period of time… if you’ve got the willpower.
“I thoroughly enjoyed taking on the Hard 75 challenge, and now I’m on the lookout for the next one.
“Challenges like Hard 75 aren’t for everyone, but if you’ve got even an ounce of willpower, why not give something a whirl?”
He also joked: “PS the tan helps.”
Paddy did not disclose the amount of weight he lost.
The presenter also reflected on his ultra-endurance cycling challenge for BBC’s Children In Need in 2024, during which he cycled across three nations and eight counties.
He said: “When I did the Children In Need challenge, it was so physically exertive that I used to kind of think ‘how did I manage that?’ and ‘how did I do that challenge?’
“I thought, ‘I’d love to do something again really out of my comfort zone’ – and that’s what I did.
“I had a bit of free time, I had about a month and a half, and I thought ‘I’m going to do it’.”
He offered advice to anyone considering a similar challenge.
Paddy said: “The best advice if you’re doing a challenge like that is don’t do too much straight away.
“It’s just about getting yourself out and doing it.”
The full interview with Paddy can be heard on Wednesday’s edition of The Scott Mills Breakfast Show.