I did an experiment. His serving size of pasta is 1/2 cup. I cooked spaghetti and measured 1/2 cup. With sauce, it makes an infant serving. I guess you would not gain weight if you ate that small of a portion. It's just a bit misleading to call it a portion. Look at your one half cup measure and you will see, without even putting cooked spaghetti in it. You could probably eat one half cup of anything, even cake, and not gain weight. However, go to any spaghetti restaurant - you will get one and a half cups of cooked pasta plus sauce. You could eat the one half cup and stay way under the 30 grams carbs cut-off point. But realistically who does that?