Americans are being urged to cut back on salt, sugar and fatty meats and to eat more fish and whole grains. The recommendations are part of new dietary guidelines issued January 31 by the U.S. government, and are designed to help the majority of Americans who are overweight or obese.  The World Health Organization says obesity is really a global problem, and nutrition experts say these guidelines are flexible enough to reflect international cultural and religious differences.  Melinda Smith reports.