AG, my lighter version of Alfredo sauce is something I made up as I cooked it, and it turned out pretty good.
I sautéed the shrimp in olive oil with a half tablespoon of butter, then removed the shrimp. I added a small amount of white wine (1/2 cup) and reduced that down, then added milk instead of cream, and simmered that a while to reduce it down a bit. To that I added 3 cloves of garlic finely chopped, S and P, and about a 1/4 cup of Parmesan cheese to thicken the sauce. I finished off the pasta for the last minute or two of the cooking time in the sauce, and then added the shrimp back for a minute to warm it up a bit.
I think if I had some condensed skim milk it would have been a good thing to try, but I didn't have any. Of course you could add more butter if you wanted to if you're not trying to loose or maintain weight.
I'm sure this still has enough calories.