I used to, rigidly. I do so now, far less formally.
If I'm going to stick to LCHF or keto, only about 20-25% of my food intake should be from protein. So much for eating the entire package of bacon :wink2: I used to measure portions with a kitchen scale.
Over time, however, my eating has become so standardized that I don't feel the need to weigh out the two eggs I have for breakfast every morning. Maybe I'll make 3 eggs if they're "medium" instead of "extra large" or I'll add or skimp a bit on the meat I add to my lunch salad.
I still buy by portions (16 oz package with four items is 4 oz per item) and I can eyeball portion sizes pretty well. So I'm monitoring it but I no longer weigh it out .