I am 19yrs. 5'4" 121 lbs. I was athletic in high school and had a bubble butt. After high school I stopped exercising and put on 15 lbs. I lost the weight quickly by dieting but now I have a little butt. Will working out perk it up or could I have lost muscle from the rapid weight loss? If my butt is not long gone what are some good exercises, also will lifting heavy weights build it up quicker? Any advice would help thanx!