The single biggest factor that prompts people into overeating is portion size, and when more and more meals are eaten outside of the home, it is restaurant portion size that can cause a problem. Not only are the portions often huge, but they set a benchmark that distorts what people perceive as an appropriate amount of food.
An obesity researcher at Penn State University had 300 chefs from fine and casual dining restaurants take a survey that asked what things influence what size they make their portions. 4 out or 5 served more than the recommended portion sizes. 70% said that presentation was the biggest concern, getting a "wow" factor into the dining experience that might cause a customer to return. Value and portion size are often connected in the minds of the consumers, so larger servings come into play more than the actual plating. 65% said that cost influenced how much food they served, and 52% cited "expectations, which was primarily true of chain-restaurants and categories (like steakhouses, for example) that are known for being generous. Only 16% considered calories.
Chefs are not necessarily dieticians and their job is not to tell you what to eat or how much of you plate to clean before taking the rest home. It does make you wonder, however, if our priorities and theirs are in the right place when a 1-pound "serving" of pasta starts to look normal.