Health's burger has about half the calories, a third of the total fat, and less than half of the saturated fat of a comparable restaurant burger--with the same muscle-building protein and delicious taste. How do we do it? We started with the best lower-fat meat choices, either ground sirloin (15 percent fat) or extralean ground beef (a mixture of different cuts), which varies between 9 and 15 percent fat. A healthy portion size is about a half-cup of meat. For more flavor, we spiked the burger with Spanish onion and Worcestershire sauce.