Q. When I lose weight, my butt doesn't decrease in length—it gets flatter and sags. What exercises would give it a lift?
A. When women diet and do cardio without strength training, they will almost always lose muscle along with fat. That is why instead of getting shorter, your butt gets flatter and the shape disappears. I am assuming you are not involved in any strength-based workout—or, if you are, the exercises are not targeting the glute complex. Strength training, particularly for the lower body, is critical for maintaining the hardness, shape, and mass of your buttock muscles. The best resistance exercises for the glute complex are the hardest ones: variations of squats, step-ups on a bench using weights, lunges done through a full range of motion, and different dead-lifts. Even leg presses on machines will help.