A Question we get asked every day here Purefit Galway: Will my legs get big from spinning? If your are genetically predisposed to have large thighs then there is not much you can do about it but Spinning is a great way to keep your thighs and the rest of you from getting fat. If you are in a calorie deficit you will not 'bulk up' no matter what kind of exercise you do. But no, spinning should not add bulk to your thighs, especially if you are eating at a deficit. Even if somehow you do manage to build the muscle there, if you lose the 10 pounds you'd likely have less fat on them, so they'd be smaller and more muscular looking. Plus, it's not like they'll get big over night, it takes a long time to build muscle.   At first they may retain some water and seem bigger, but once it lets go they'll pretty much feel back to normal. After I work my legs my jeans are always a bit tighter, but usually by the next day they're fine. So don't eat too much to feed the muscle. It takes a very high protein diet and hours in a gym lifting seriously heavy weights to get bulky. You would have to give up your job and work at those legs full time to build them.