"My whole family is obese and stuff and that was my goal, not to die that way," Tyson told digital radio station SiriusXM.
"I didn't want to die that way. And I respect them and love them, don't judge them, I just didn't want to live my life like that. I didn't want to restrict my life.
"You are what you eat. I don't eat bread, I don't eat nothing like carbs, like potatoes. I don't eat nothing that puts on weight, nothing that has a calorie.
"I eat the things with the least calories possible. Blueberries, fish or something that's very rare.
"Lately it's a plant-based diet and I may eat some fish or chicken every month or two. But other than that just plant-based, fruit, and all that stuff. And hard cardio."
It comes after the American boxing legend hinted his return to the sport.
He first sparked chatter about a potential comeback after wowing fans in a ferocious sparring session in a video that went viral.
Tyson, who hasn't entered the ring as a professional in 15 years, has posted another impressive sparring video on social media before saying "I'm back".
"Can you imagine me and him going in the ring together as arch enemies, doing it for the humanity of people, for people less fortunate than ourselves. What would that be like?
"That's something that's never been done by any entertainer or any sports figure in the history of sports."
Tyson says his focus at this moment in time is to enjoy sparring again but he insists "anything's possible".
"Hey look I'm just having fun, looking good, showing off my new bod and stuff," he said.
"Anything's possible, My ego is starting to get elated and stuff that I'm capable of doing things but we'll see right. The future's got a lot of things on hold for us.
"There's a lot of people out there that need help and something like that [an exhibition fight] could help a lot of people that need help. That's basically what I've embarked on, a life of charity and gratitude."
