Some people through the desire to wear corsets very tightly or the want to reduce their waist line will wear corset very tightly for extended periods of time in a process known as waist training or tight lacing. This process can actually permanently alter you waist line which is an obviously attractive proposition but there are health implications. lets start with the positives. Firstly tight lacing can reduce the size of your stomach which in turn surprises your appetite, this is pretty good plus. Secondly the process will reduce your waistline. If you do this in moderation and know when to stop this can be a fruitful process. 1-2" from your waistline will look natural and the experience may only take 3-4 weeks. If you try past further reduction form here you are asking for trouble.
First and foremost this type of waist reduction is not the same as when you exercise and diet appropriately to lose body fat, exercise and good diet will increase muscle mass and give a uniformed and well proportioned, honed look. very desirable. Too much waist training will actually give a more circus freakish sort of look as you are not working any other regions of you body during the process, just your waistline is going to appear skinnier but without definition.
In fact while you are wearing your corset this tightly the garment is doing a lot of work for your stomach and back muscles. They are actually wasting away through atrophy. You will also have health problems with this type of reduction. Internal organs will now start to be displaced as they are all forced upwards by the pressure of the corset. This usually result in pressure on the bottom of the lungs which will begin to shrink through time lowering you lung capacity.
If you are realistic in your goals for waist training and complement you 1-2" waist reduction with back and stomach strengthening exercises then it is an easily achieved comfortable process, but do not attempt to go over this sort of reduction without seeking advice from a medical professional.