The Benefits of Peptides for Muscle Growth and Fat Loss Theres a lot of confusion around peptides and muscle., Heres how I actually think about it., Most peptides dont build muscle directly., They improve the systems that allow muscle to grow., First, IGF 1 LR3 PRAMAH THE HAVEN IGF 1 LR3 does not promote growth in late gestation growth restricted fetal sheep American Journal of Physiology Endocrinology and Metabolism American Physiological Society