I actually DID notice this. Initially, I started Primal with conventional meat. When I was able to budget in better meat, I switched over to the TJ's grass fed ground beef (5.99/lb) and ribeye steaks (10.99/lb). I didn't notice that I was eating less until it dawned on me I was spending almost the exact same amount per week on groceries as when I was eating conventional. That's when I started tracking the quantity of food I eat, and it's about 1/2 of what I ate on conventional. My thoughts were that my body is better nourished now and doesn't signal me to eat more to get the same level of nutrients.
"You can always do more than you think you can !" Sensei Scash