The Big Lebowski star is known for his heavy frame, but he has been steadily shedding the extra weight in recent months, and reports suggest he is now 100 pounds (45.36 kilograms) lighter.

John, 63, admits he doesn't know if the claims are accurate, but he's happy to finally be able to shop for clothes in regular stores, instead of heading to specialist big and tall outlets.

"I have no idea how much I lost; I didn't weigh myself," he told U.S. breakfast show Today. "I just... clothes fit nice (sic) and I can go to nice clothing stores and buy too much stuff!"

However, John, who is no stranger to yo-yo dieting, isn't promising to maintain his healthy new lifestyle forever.

"Just wait another six months and I'll be back to normal!" he joked. "That's the way it goes!"

John may not be keeping tabs on his weightloss journey, but his trainer, MACkie Shilstone, previously revealed the actor's slimline new look had been a long time in the making.

"This didn't happen overnight - it's been an ongoing process," the fitness guru told People magazine in November (15).

MACkie introduced John to a more Mediterranean-style diet, heavy in fish, fruit and vegetables, and encouraged him to work out six days a week, helping to trim the extra fat over a couple of years.

"There needs to be strategic planning," MACkie explained. "This time, he really wanted to do it."

John, who quit drinking in 2007, has also been open about his weightloss struggles, and after pushing 400 pounds (181.4 kilograms) in 2011, he decided he really needed to make a significant lifestyle change.

"I decided to stop stuffing food into my mouth every five minutes," the former Roseanne star told U.S. shockjock Howard Stern of his new diet earlier this week (begs07Mar16). "Turns out I was just eating all the time. Anytime I had my hands open or free, I shoved something in my mouth. It's all crap."

"It's been a year and half, I did it slowly," he continued of his latest lifestyle revamp. "I used to go on these diets, take three months and lose about 60-70 pounds, feel great, and reward myself with crapola (candy). Twinkies (sugary cake bars) look good."