No Gym? No Problem! This Is the Perfect At-Home Workout to Bust Through Belly Fat

These are like sit-ups, only way worse (but in a good, ab-defining way). "This exercise is great because it really works your whole core," Ferraro said. "You hold a medicine ball at your chest. When you sit back reach behind your head with the ball, and feel that stretch. When you sit up, press the ball to the ceiling. This mimics the motion of a punch, and also helps tone the arms!" He recommended doing three sets of 10 to 15 reps.

Ah, HIIT. You've seen these four letters time and time again in your quest for a flatter stomach — and if you haven't tried it yet, you should add it to your routine. "High-intensity cardiovascular activity is one of the most effective ways to rid your body of belly fat," Diamond said. "Several studies have shown that HIIT is very effective in reducing overall abdominal fat! This is done by alternating short bouts of all-out effort with short bouts of recovery." She recommended doing 30 to 45 minutes of HIIT three times a week. Need ideas? Try this at-home HIIT workout.

"OK, so we all dread these," Lagree said, "but I promise you, they work." But in order for mountain climbers to work properly, you need to have good form. "To begin, position your body in plank. Pull your right knee into your chest. As the knee draws to the chest, pull your abs in even tighter to be sure your body doesn't stray from the plank position. Then, quickly switch and pull your left knee in." Keep repeating. Lagree recommended working up to three one-minute intervals with quick rests in between.

Again, form is key for these to work. "A common misconception is that mountain climbers have to be done fast. Rather, whatever your speed, be aware of your body positioning and core stabilizers," Lagree said.

Bad news: according to Ferraro, your lower abs are the trickiest place to get definition. The solution: "Getting a good dose of classic left lifts in will help you whip them into shape," he said. "Lay at the base of your bed, and grab the post. Slowly lower your legs to the floor, keep them locked out straight, and do not let your heels touch the floor. These burn baby!" He recommended doing three sets of 10 to 15 reps.

Russian twists are great for targeting your obliques. To start, sit up straight on the floor with your knees bent and heels about a foot away from your body," Lagree explained. "Then, slightly lean back without rounding your spine. This part is particularly important (and yes — it's going to be hard!) but don't let it curve or the exercise won't work. Hold a weight with both hands in front of you. Then while pulling your belly button to your spine, twist slowly to one side. Hold for three seconds and inhale, then rotate to the other side." He recommended working up to 16 full rotations (left and right is one rotation).