3 Mistakes You're Making at the Gym

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You have unrealistic expectations

Don't be a slave to the scale, and don't expect to see aesthetic results for the first month, says Bah. "If you're training correctly and incorporating weights and cardio, you may actually see the scale go up at first because you're adding lean muscle mass," he says.

So instead of vowing to lose 15 pounds, set a more concrete and attainable goal—like participating in a breast cancer walk or running a half-marathon, says celebrity trainer Jennifer Cohen. You'll slowly start to see your body change as you work to meet your goals.

Next: You haven't changed your diet