The issue is that humans are not deterministic machines. We are often presented with internal urges and cravings. We are faced with stresses that lower our abil

The issue is that humans are not deterministic machines. We are often presented with internal urges and cravings. We are faced with stresses that lower our ability to maintain discipline. We have different needs, so you can't just adopt a one size fits all plan. And we do have different microbiomes that will create all sorts of issues with respect to our ability to make decisions, exercise and recover. So while it is fundamentally true that a calorie deficit will lead to weight loss, it's not trivial to create a consistent deficit while maintaining good nutrition.