If I had said we were testing the effects if Mr. Body changed from a 2,000 calorie diet to a 2,500 calorie diet, would you be saying "Mr. Body now feels full and bloated, so he decides to switch back to 2,000 calories a day"? No, we'd be talking about the biological adjustments in what get burned and what gets stored, and that he would be gaining about a pound of body fat a week.
If I had said we were testing the effects if Mr. Body changed from a 2,000 calorie diet to a 1,500 calorie diet, would you be saying "Mr. Body feels hungry, so he decides to switch back to 2,000 calories a day?" No again, we'd be talking about the biological adjustments in what gets burned and stored, and that he would be losing about a pound of body fat a week.
If we wanted to compare Mr. Body eating his 900/700/400 CFP diet with his twin, Mr. Body Double, who eats a 600/1000/400 CFP diet, would you be saying "Mr. Body Double feels greasy, so he gives some of his Crisco to his dog, Mr. Dog, under the table and sneaks a Snickers bar at night"? No again.
If we wanted to discuss Mr. Body going full-on vegan, would you be saying "Yup, he's vegan, But once a week he runs through the McDonalds drive in because Big Mac attack."? Once more, no.
Yes, when people decide to eat more, many revert back to their old portions.
Yes, when people decide to eat less, many revert back to their old portions.
Yes, when people change diet proportions, many revert back to original patterns.
Yes, when people eliminate some foods, many cheat or slip back.
He feels hungry. Fine. That's an effect. Then measure the effect. Have Mr. Body report his hunger levels while we're monitoring his blood glucose and taking his weight.
IF the question is "Will Mr. Body stick with eating 900/700/400 C/F/P when receiving additional insulin?", then dietary modifications due to hunger is an acceptable things to allow and monitor.
But when our question was "What happens to Mr. Body, eating 900/700/400 C/F/P, when he receives extra insulin", the hunger stops at hunger.
Answering "Mr. Body eats a snack" means we are now answering the question "What happens to Mr. Body, eating 1000/700/400 C/F/P and receiving added insulin."