I'm 5'7 190, and bought the XL. I have it on the first set of hooks and it def sucks everything in as you're  hooking the clasps. You do feel a change in your breathing when its finally on. But I've noticed its your body getting used to the form of the waist trainer. Going to try it out this week while at work to see how I do. Excited to see if their are results. It Makes a difference under your clothes! You immediately look more shapley and fit.