With obesity much on Americans' minds, an entire industry has sprung up selling diets and diet books, meal replacements and exercise programs, nutritional supplements and Internet-based coaching, all in an effort to help people lose weight. But a new study, published today, finds little evidence that commercial weight-loss programs are effective in helping people drop excess pounds. Almost no rigorous studies of the programs have been carried out, the researchers report. And federal officials say that companies are often unwilling to conduct such studies, arguing that they are in the business of treatment, not research. "In general, the industry has...