FILE - In this Jan. 20, 2010, file photo, a waist is measured during an obesity prevention study at Rush University Medical Center in Chicago. The bathroom scale may show a good number but how much of that weight is fat, not muscle? New studies are adding to the evidence that the scale doesn't always tell the whole story when it comes to weight-related health risks. (AP Photo/M. Spencer Green, File)WASHINGTON (AP) — The bathroom scale may show a good number but how much of that weight is fat, not muscle? New studies are adding to the evidence that the scale doesn’t always tell the whole story when it comes to weight-related health risks.