This is well-intentioned but I think it oversimplifies in ways that can actually be harmful. "Just get used to being hungry" is rough advice to give people - chronic hunger is one of the main reasons diets fail, and framing weight loss as a willpower contest against hunger ignores that satiety is heavily influenced by _what_ you eat, not just how much. A 400 kcal meal of protein, fat, and fiber will keep you full for hours; 400 kcal of simple carbs will leave you hungry again in 45 minutes, in part because of the insulin and blood glucose dynamics involved.
The calories in/out model isn't wrong exactly, but it's so reductionist that it becomes misleading in practice. It omits hormonal responses (insulin, leptin, ghrelin), the thermic effect differences between macronutrients (your body burns 20-30% of protein calories just processing them vs 0-5% for fat), gut microbiome composition, sleep quality, stress hormones, meal timing, and individual metabolic variation. Two people eating identical calorie counts can have very different outcomes. Telling someone "just eat less and accept the hunger" without any of that context can set them up for a miserable yo-yo cycle - or worse, a disordered relationship with food.
