Practicing Pilates equipment can help thin arms. Pilates is a comprehensive form of exercise, emphasizing the core strength and stability of the body. By using instruments, such as barbells, dumbbells or elastic belt, the difficulty and effect of training can be increased. Pilates gymnastics can exercise arm muscles, including biceps, triceps and shoulder muscles, thus helping to slim down and shape arm lines. But if you want to lose weight, you need to combine proper aerobic exercise and diet control to reduce fat in an all-round way.