Make your sauce CHUNKY with LOTS of veggies( tomatoes, onion, mushrooms, spinach, squash etc) It should be like a stew..Don't let it get "runny" . Boil 1oz whole grain pasta per person and when done- use kitchen shears to snip into small pieces. Mix into sauce and divide into servings. The veggies make up for the lower amount of pasta. And because it isn't a mound under the sauce- no one can gage how much( or little) pasta they actually have.!
Using the whole grain pasta will add fiber so that you feel fuller than you would from reg pasta as well. My Italian hubby hasn't noticed that he is only eating 1oz of pasta per meal in a YEAR! ( he used to have 6-8oz by himself!)