Something like this one you mean?They said nothing on the BBC programme about metabolism starting to slow. Prof Taylor said that if you follow his diet with eating two thirds of what you ate before you will maintain the weight loss. I did this and not only maintained the weight loss but have lost a further couple of pounds since I finished the diet at the turn of the year! Its a bit of a sweeping statement that "most people know" that its almost impossible''' "as your metabolism slows..." People often do start to regain but have you any proof that its to do with their metabolism slowing - at least for any length of time - or is this an urban myth? Perhaps its just that they return to their former eating habits?
https://onlinelibrary.wiley.com/doi/epdf/10.1002/oby.21538