Low-Calorie Protein Sources?

shrimp, scallops, fish, poultry, lean cuts of pork, lean cuts of beef.

Canned chunk light tuna is 90 calories for 5oz.

If you want a really thorough source of information, check out this spreadsheet:
https://community.myfitnesspal.com/en/discussion/10247171/carbs-and-fats-are-cheap-heres-a-guide-to-getting-your-proteins-worth-fiber-also#latest

Seafood, egg whites, beans, Greek yogurt, lentils, tempeh.

I like to get some fiber with my protein so that I can got two birds with one stone. I will use chick peas instead of ground beef in pasta sauce. I also like marinated chick peas. For an animal source my preferences are 97%lean turkey, and tuna packed in water. Tuna keeps my full and has a whole host of other nutrition.

Chicken or eggs
Egg whites! Cook in a muffin pan with veggies for breakfast

Chickpeas, beans, tofu

i love built bars!

https://builtbar.com?baapp=SCRIPTSANDSPOONS

Shrimp is on my plate at least 2 times per week. At 25g per hundred and only 100 calories, it is hard to beat with anything good.

I typically saute the shrimp in Pam with crushed red pepper flakes, but, when calories are available a pat of butter is also good.