Many patients who are seen by gastroenterologists are overweight or obese. Moreover, gastroenterologists often are consulted to help manage obesity-related gastrointestinal diseases or gastrointestinal complications of weight loss therapy. Therefore, it is important for gastroenterologists to understand the key clinical issues associated with obesity that are discussed in this issue. In addition, gastroenterologists can provide a valuable clinical service by becoming actively involved in helping their obese patients lose weight.