Jack Black’s Battle of the Bulge! Comedy King Sweats to Save His Life

Jack Black is finally embracing a fitness plan — but sources warn that the Jumanji star needs to stick with the program and focus on his health to fight the possibility of an early grave!

The funnyman, 55, recently shared a video on Instagram showing him pumping iron at the gym — and tipsters tattle that’s a good thing because the colossal Kung Fu Panda cutup is crushing the scales at a tremendous 250 pounds!

“It’s about sweat equity,” Black jokingly blabs while hoisting dumbbells. “It’s about putting in the work. It’s about putting in the grind.”

Mentioning his musclebound Jumanji costar, he quips, “It’s about keeping up with the Dwayne ‘The Rock’ Johnsons of the world.”

An insider dishes, “Jack is swearing up and down this is for real this time. He wants to shed 30 to 50 pounds and maintain it with a carefully balanced, nutritious diet and workout plan laid out by professionals. People around him agree he shouldn’t do it on his own. He needs help.

“He can’t go on walking around with that much weight around his belly, so bravo to him for doing it!”

Florida-based longevity expert Dr. Gabe Mirkin, who doesn’t count Jack as a client, tells The National ENQUIRER, “He has a massive abdominal obesity. That means to me that the odds are overwhelming he’s already diabetic and already has some of the complications of diabetes.

“While the exercise program is good for him, he also needs strict dietary control and perhaps medication. Diabetes markedly increases his chance of getting a heart attack, so he really should check with a doctor immediately, if not sooner. I expect that the doctor would also put him on heart attack– preventing medication!”