Jillian Michaels Reveals How to Burn More Calories in Less Time at the Gym

Jillian recommends metabolic circuit training, which is performing exercises in succession with no rest in between moves. If you really need a rest, she said you can take a one-minute maximum break in between circuits. She also said to add a HIIT interval into each circuit.

Some examples of good exercises for metabolic circuit training include mountain climbers, burpees, and jumping rope.

Multiple muscle group movements, or compound exercises, are exercises that incorporate multiple muscle groups at the same time.

"Exercises that incorporate multiple muscle groups at the same time not only burn more calories because they are requiring more effort and energy to perform, but because they work different muscles at the same time, they kill two birds with one stone: You don't have to be in the gym as long," she said,

"Interval training is always going to be extremely efficient because it gets the work done faster," Jillian explained. "You tax your body at 100 percent so it requires less time in the gym overall. Plus, it amps your calorie burn during the workout as well as your EPOC, or afterburn. And it accelerates how quickly you get fitter because of the intensified stress adaptation response."