Earlier quoted context omitted.
Eat less calories than you use each day. (fullstop!) While true, that statement is useless. It doesn't take into account the effect insulin has on the ability one has to actually take in those fewer calories. It also doesn't take into account metabolic pathways that allow one to eat more of certain kinds of foods than others. The scientific literature is pretty clear (once you filter out the government propaganda tha…
You're still making it way too complicated. If I put 10 gallons into my tank every day, but use 11 gallons daily.. I'm "using up" gas. That's all that matters. Of course, there are many, many, many tweaks to be made, but for the majority of people, who need to lose a massive amount of weight, if they eat less calories than they use, they will lose weight. End.
Maybe it just is that complicated (not that I view the above as complicated, I just don't view it as simple as you make it).
> If I put 10 gallons into my tank every day, but use 11 gallons daily.. I'm "using up" gas. That's all that matters.
Imagine an engine that behaves differently depending on the type of fuel is put in it. One type of fuel causes the engine to move slower and burn less gas per unit time. So you may continue to put in your 10 gallons a day with this new fuel, but you'll notice a surplus building up because it only burns say 5 gallons a day because of this change. The output you get from the engine varies depending on what is put in it.
That's what the parent was describing. Calories in and calories out are not independent variables despite how they are treated in some research and most popular media. The type and amount of "calories in" affect your energy level (calories out) and hunger level (ability to limit your caloric intake).