The opera singer - who was last night's Britain's Got Talent runner-up with singing partner Charlotte Jaconelli - said that he will not change his habits if asked to by record producers.
"I wouldn't change for no-one - take me or leave me," he told The Sun.
"Diets aren't my style. If Simon said I had to change my image I'd say, 'No, thank you'. If he said I had to slim, I'd say, 'No. It's a good offer but I am who I am'."
He added: "If there's any negativity I'll take it in my stride. I have good friends and family and I'm a lot happier than I was back then - happier than I've ever been."
Simon Cowell is rumoured to be offering Jonathan & Charlotte a £1 million record deal following their appearance on the show.
Antoine's mother recently revealed that her son had become a recluse after he was bullied at school.
Watch Jonathan & Charlotte's final performance below: