Restaurant portion sizes are often much larger than the serving sizes in the U.S. Department of Agriculture's Food Guide Pyramid. For example, officially, one serving of bagels is equal to about 2 ounces, but just try to find a restaurant bagel under 4 ounces. One official serving of salad dressing is 2 tablespoons, but restaurants typically put about twice as much on your otherwise perfectly healthful salad. Unfortunately, most Americans just don't get it. Don't place all the blame on the food industry, though.
Restaurants only sell what consumers want.
If consumers think value-sized bargains are more important than portion control, then restaurants will continue serving them. Order one main dish and split it between two people. Ask for toppings and dressings to be served on the side. Leaving food on your plate isn't a crime. Order smaller sandwiches or kids' meals.