I don't think I've ever seen a prix fixe/chef's selection menu that wasn't going to leave me absolutely stuffed. If you go somewhere and order a la carte and plan to spend "normal" nice restaurant prices (say, $30-40) sure you'll get a smaller size. But if you're spending like $70+, you'll almost always leave full. The one actually starred restaurant I went to, I skipped lunch and could still barely walk home it was so much food. 6-12 courses add up, even if they're small.