What is the best advice for building lean muscle mass? I’ve lost a lot of fat weight over the past couple of years, but I’m really struggling to put on muscle mass and definition. I’m an 18yr old 5’10 female, weighing about 135lbs. I’ve talked to a nutritionist, and trainers about this, and nothing has worked so far. I’m also Majoring in Exercise and Fitness Science, and have yet to learn about what would help ME. Thanks!