It depends if you have insulin resistance. You could start out with a low-carb diet (be ready for zero energy in the beginning) and see how it affects you. There is also a diet called the Insulin Resistance diet and my personal favorite is the GI (Glycemic Index) Diet (there is a good book for this). I mainly got on it to lose a little belly cushioning. I am one of the thin PCOSers, with a BMI of 22, but I have more cushion around the middle than I would like to. After stopping BCP I gained about 10lbs and I'm pretty sure it was straight around the middle, lol.