I think there is a distinction to be made. You can explain IF to someone in 5 minutes and they can do it tomorrow. That’s how I heard about it. Nobody owns the idea.

Taking your example, Lean Gains is a niche application for men trying to improve their physique, and it includes exercise and motivational components. This is pretty different to the Atkins diet for example, where the book is the diet, and they don’t really exist independently.