June 30 (Reuters) - The U.S. Food and Drug Administration said on Monday it is revising the labeling of all extended-release stimulants used to treat attention-deficit hyperactivity disorder to include warnings about the risk of weight loss and other side effects in patients under six years old. The FDA said that it is requiring a "limitation of use" section in the prescribing information of all extended-release stimulants to include a statement on higher rates of adverse reactions in children younger than six years.