Calories in, calories out. That has turned out to be basically accurate, according to numerous nutritional studies, although nutritionists can tell you a million ways that you may be influencing calories out that were not aware of.
Tirzepatide has been tested to see if it increases metabolism. Tirzepatide has little effect on overall metabolism.
People are poor historians of their dietary habits. (I exempt serious body builders from that generality. They have to be precise in what they eat since they're constantly intentionally going up or down in weight.) I believe it feels like he's eating the same amount of food. He's being a normal human by thinking so.
I recently had to stop retatrutide due to possible liver problems. I'll likely start again soon. On the tirzepatide alone, I don't feel like I'm eating too much. However, my weight keeps increasing. The FEELZ test for how much we're eating is usually a poor indicator. Keeping dietary records, is strictly followed and accurately done, reveals valuable information but it's unusual for a person to consistently and strictly track all food and exercise.
Apparently, reta causes a slight increase in metabolism. Mazdutide also causes an increase in metabolism.