[tomhoward]

It’s an argument that is as old as the hills and relies on the assumption that the body functions like a simple furnace, which of course is false.

Metabolic rates vary significantly, and rates of absorption of nutrients and consumption of energy vary a lot as a result of factors such as inflammation and endocrine function.

Calories in/calories out may still ultimately be true when you boil it down far enough, but the factors influencing and intervening in those processes are vastly complex and strongly affected by diseases and dysfunctions that are very common.

Thyroid disorder (which can include cancer or a precursor condition) is probably the most common/known, but just one of many.