Mr. Olajide, 45, was born in Liverpool, and came up in the ring in Vancouver, until his contract was purchased by Madison Square Garden in 1986. In a title fight against Tommy Hearns in 1990, he suffered irreparable damage to his right eye, and now wears a stylish custom-made silver patch over it. He has become the go-to guy for getting stars a nice boxer’s physique in record time. He worked with Will Smith for Ali, and Josh Hartnett and Aaron Eckhart for The Black Dahlia.

But recently, models and their agents have also zeroed in on Mr. Olajide’s workout regimen to “sleek-ify” their bods before a big cover shoot. “Adriana started coming in for the GQ cover, Karolina is doing some magazines and had a G.I. Joe movie, and Doutzen has a Calvin campaign coming up, I think,” Mr. Olajide said.

The boxer and his partner, former ballet dancer, Leila Fazel, are just about to release a new workout video called CTBS, which stands for Cut the Bullshit. On a recent Monday, the Transom tried to make it through one of their hourlong Aero-3 classes, also a favorite of the models; it involves a lot of punching, jumping rope, squatting, push-ups and weights.

“I think they like it because it doesn’t bulk the body,” Mr. Olajide said. “It definitely lifts the ass and narrows the waist.

“Karolina hits hard,” he shared. “Doutzen loves the jump rope, she used to speed-skate. Adriana loves the mitts and the speed bag.”

Movie mogul Harvey Weinstein is also a client of the gym, Mr. Olajide said. “He’s not a ropes guy … but put it this way, you don’t want to get hit by him.”

Reps for the models and Mr. Weinstein did not return calls.