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At the gym: Balance

Your abs get used to routine, Fisher explains. Vary your exercises every time you hit the gym. (Throw in a new move or two, or try your usual ones on a stability ball.) You can also switch up your entire routine every month to keep your stomach guessing—and shrinking.

To make your core work to stabilize your body (which strengthens abs), do moves one arm or leg at a time. A strong core helps you stay injury-free and gives you a pulled-in tummy, Fisher says.

Tight hip flexors can lead to an imbalance that makes your spine arch and pelvis tilt out, emphasizing your belly, says Susan Paul, training-program director at the Track Shack Foundation.

To loosen hip flexors: Kneel on one knee, other leg bent, foot on floor; press pelvis forward until you feel a stretch down the front thigh of kneeling leg. 

Next: At the bar