There are two books which will help you. One is Perfect Digestion by Deepak Chopra. And another is Yoga for Digestive Disorders by the Bihar School of Yoga. The latter is particularly helpful because it gives individual attention to specific digestive problems, including overactive metabolism which prevents weight gain -- very detailed about food items to be taken or avoided. You may find it at Landmark bookshops or place an order or order from the ashram directly.