Hi RCH...I assume, maybe incorrectly, that your IBS symptoms are diarrheic prone vs constipation prone.If you can isolate and avoid all foods and additives and other (psychological) events which provoke the intestinal release of mediators, your symptoms will subside, digestion will improve, and nutrient utilization as well.This may, however, be accompanied by a temporary weight loss as many patients are carrying around a few pounds of water weight as a consequence.Once you have achieved symptomatic remission, a dietician can show you how to consume 300-500 more calories a day than your present baseline and thus gain about a pound a week.The caveat is that you have some normal base weight sort of genetically-programmed into your body, so passive caloric manipulation will usually only allow a person to alter their weight about +/- 10% around that normal weight...then the body starts to make adjustments to prevent further gain or loss depdning upopn which way you are going. Hence the program of weight gain or loss can become more arduous as one has to alter ones level of activity under supervision in such a fashion as will allow for the addition of more body mass....or less as the case may be.To better understand, if my guess is correct about your symptoms, your options in how to first get the ssmptoms you have under control these books think you will find helpful:IBS: A DOCTORS PLAN FOR CHRONIC DIGESTIVE TROUBLESBy Gerard Guillory, M.D.; Vanessa Ameen, M.D.; Paul Donovan, M.D.; Jack Martin, Ph.D. http://www.amazon.com/exec/obidos/ASIN/088...3369143-6824157 "FOOD ALLERGIES AND FOOD INTOLERANCE: THE COMPLETE GUIDE TO THEIR IDENTIFICTION AND TREATMENT", Professor Jonathan Brostoff , M.D.. Allergy, Immunology and Environmental Medicine, Kings' College, London http://www.amazon.com/exec/obidos/ASIN/089...6487508-3420903 MNL