"Gary Taubes article says that American medical establishment may have caused nation's obesity epidemic by recommending low-fat, high-carbohydrate diet for last 25 years and that Dr Robert Atkins may well have been right all along in telling Americans that they can lose weight by eating all the fatty foods they want and skipping carbohydrates; says Americans' total calorie intake has risen considerably under government-recommended diet because of way carbohydrates affect blood sugar and insulin and thus appetite; notes research indicating that ketosis, hunger-reducing mechanism in Atkins diet, is safe, that Atkins-like diets can be more effective at weight reduction than low-fat diets and that they may even be better for the heart; welcomes NIH's belated decision to finance comparative studies of popular diets; photos (L)"
