How are you sure it is your primitive brain talking and not your prefrontal?

So I am trying to push myself to get to the other side of my weight loss goal. Sticking to my plan will get me there, I know this for sure. It is when I don’t plan or eat off plan that my weight loss stalls. Anyway, I am continually working with intermittent fasting in the morning to hopefully give me an edge. Long about 9-10:30 my stomach starts to growl, I get this feeling in my mouth of wanting to eat and I start coming up with reasons why I should eat. “My stomach is growling, I feel like I want to eat in the back of my throat but it isn’t time. Just eat something to get you over the hump.” Is it my primitive brain or my prefrontal? Maybe it is reasonable to eat if my stomach is growling and I feel hungry? Should I assume it is my primitive brain since this would not be consistent with what I have planned for myself? I know I can make the time to lunch I have done it before but am I forcing the issue and white knuckling it so to speak?