Whatever you say probably won’t change someone’s mind honestly. Even here in the forums people still cling to CICO. “If I ate to satiety, I’d be able to eat forever.” This is fat to satiety, not protein which is the example food the other person usually gives, a high protein one.
When I try to explain it, I don’t explain CICO. I explain insulin in basic terms as well as how the body uses fuel. It gets a little long but includes examples.
The first thing your body burns off above all else is alcohol because it’s toxic in high amounts, the next is glucose for similar reasons. If you look at a SAD fancy breakfast, you’ll have a mimosa or champagne, pancakes with syrup, orange juice, toast, hash browns, eggs, bacon. Your body has to go through the alcohol first, sugar second. So, it’s working through this glucose and the bacon and eggs are waiting their turn but, before you get to them BAM lunch time. You eat a sandwich, chips, and a coke. More carbs to work through. Eventually the fattier foods will break down and be shuttled right to storage because carbs are first. So, working along and here’s dinner. Steak, mashed potatoes, flour gravy, maybe you eat a side of broccoli to be “healthy.” More carbs to work through, more food to store from before that you never got to. It’ll store anything extra because it has to until it can get to it. If we spend all day eating carbs, carbs, carbs we never get through them. Our blood glucose stays high. If blood glucose is high, so is insulin. If insulin is high, so is fat storage.
I actually just went through this with my own mom. She secretly went keto a month ago but still refuses to eat more. So now she has low energy and hunger problems.