Training to sit for food teaches restraint and can start early in training. With me, momma started on my gotcha day, when I was a wee pup of 7 weeks. Every time she fed me, she’d put my little fuzzy butt into a sit, say “sit”, then say “Ok” & give me a gentle pat on the shoulder, and (finally!) let me have my food. She did this over and over, every time she fed me, and it didn’t take long for me to understand. The physical pat on the shoulder reinforces the “ok” (or whatever your release word is).