Billy Bob Thornton is sharing his health challenges and how they led to his extreme diet.

During a recent appearance on the “Howie Mandel Does Stuff” podcast, the 70-year-old actor revealed the lifelong health battle that has influenced his strange snacking choices.

“My diet’s very restricted. Well, I’m allergic to wheat, dairy. I have type AB negative blood, which is the rarest type in the world. It’s like less than 1% of the population of the world has it,” he explained. “It means you have less digestive enzymes. That’s one of the things that goes along with it. But I just grew up with a lot of allergies.”

He went on to list some of the dietary restrictions that come with his condition, saying he can’t eat dairy, wheat or shellfish, as well as meat, including “pork or beef or any of that stuff.”

The “Bad Santa” actor has gotten a handle on his health and nutrition, noting for breakfast that morning he had a bowl of blueberries, and that he planned to indulge in “some gluten-free chips with some dairy-free cream cheese” when he got home.

“When I was a kid, you know, I grew up in Arkansas and East Texas and I ate everything,” he said. “I just assumed everybody felt like s—t after they ate. I didn’t know.”

His many dietary restrictions have led to some adventurous snacking. During the interview, he discussed being in the green room before a “Landman” Q&A event and not seeing anything that was safe for him to eat.

While looking at a plate of deli meats, cheeses and crackers, Thornton found some grapes he could munch on, and after thinking, “OK, so I’ll be bored as hell with this,” he found an unlikely item to pair it with.

“I dipped this grape in the Dijon mustard,” he said. “It had It was one of the best things I ever had in my lifetime. So now it’s become a thing for me.”

As a younger actor, Thornton was known for undergoing drastic body transformations for his roles, but during an interview on “Late Night with Seth Meyers,” in January, he shared he won’t do it anymore “because it does not feel good.”

He recalled gaining 60 pounds for roles in “Tombstone” and “U Turn” in the late 1990s, and then later did a movie called “Pushing Tin” for which he “got down to 128.”

“It’s funny — if I ever see a picture of those days, because this is back … when you’re a younger actor, you’re like, ‘Well, I’m going to gain 75 pounds for this, and the next time I’m going to do this,’ and whatever, ‘I’ll cut my own cheek,’ you know, that kind of thing,” he said with a laugh. “After a while, as you get older, you stop doing that stuff.”

Thornton is currently starring in the popular Paramount + show “Landman” alongside Ali Larter, Demi Moore and Sam Elliot.

The show focuses on roughnecks and billionaires in West Texas who are trying to get rich as the oil industry continues to take over the state.

“I think the thing that I learned that I wasn’t quite aware of before — because I knew some about the oil business — but I knew people more on the sort of suit side of it, you know, in Texas,” he told Fox News Digital in November 2025. “One of the things that surprised me was how many people who had had broken lives are working in the oil fields. Got ex-cons and all kinds of things working out there because they can make from $120,000 to $180,000 a year to take care of their families when they try to straighten their lives out.”