The Federal Trade Commission, which works with the FDA to investigate deceptive advertising, said weight-loss programs, particularly those that rely on supplements, are a $25 billion industry that "all too often" makes false or unproven health claims. The FTC said it has filed more than 120 cases challenging supplement advertising in the past decade.

Here are seven questionable weight loss claims — featured in the Federal Trade Commission's Gut Check — that experts say simply cannot be true:

• Causes weight loss of 2 pounds or more a week for a month with no dieting or exercise

• Causes substantial weight loss no matter what or how much one eats

• Causes permanent weight loss, even after the product is discontinued

• Blocks the absorption of fat or calories to provide substantial weight loss

• Safely allows weight loss of more than 3 pounds a week for more than four weeks

• Enables all users to lose substantial weight

• Ties weight loss to wearing a product on the body or rubbing it into the skin