> I’ve never believed this — only because my weight is so consistent and my eating is not.

That's only one side of the equation.

It is a basically proven fact (and largely implied by physics) that `calorie intake - expenditure = net weight change`. That is pretty much beyond dispute.

It is also true that some things affect expenditure, and it seems likely that most people have a "set point" that your body attempts to return to. This is also almost certainly changeable, as people have managed to change it in the past. (And this is less surely true than other things known.)

So yes, it's entirely possible to eat "inconsistently" and not have net weight change, your body is probably subconciously causing you to eat less after you eat large meals, and vice versa. Or possibly causing you to expend more energy after large meals.