Getting some form of physical exercise is still important when dealing with IBS. Exercise promotes blood flow & helps remove toxins from the body. Movement also will help the gut remove gas, reducing bloating.
IBS can cause fatigue which may hamper your ability to do strenuous exercise. However, you may still be able to do low or no impact exercises. If you are not maintain your weight, then I would not recommenced exercising as this will only make you lose more weight. You may want to consult your doctor before engaging in any sort of exercise regimen.