This seems like a huge premature optimisation. Reduced-calorie diets result in clinically meaningful weight loss regardless of which macronutrients they emphasise [1]. For someone who wants to lose weight or maintain their current weight, eating a calorie controlled diet is the first (and often only) thing they need to do.
Eating a calorie-controlled diet is primarily a psychological challenge. They should therefore eat with whatever frequency and quantity they personally find makes sticking to a calorie-controlled diet easiest, whether that's eating 2 meals a day at 07:00 and 13:00, or eating 5 meals a day, or eating 1 meal a day at 21:00, or whatever works for them.