There is no documented scientific evidence that colonic irrigation helps with weight loss.  It is based on the dubious theory that fecal material accumulates in the colon and releases toxins to cause ill health.  Colonic irrigation is denounced by several professional organizations, state health departments, and the National Council Against Health Fraud.  The procedure had resulted in serious infections, bowel perforations and even death.  It can interferes with natural elimination and may lead to the overuse of laxatives.  But for a different point of view, read about colonics from the Guide to Alternative Medicine at About.com.