True but completely disingenuous. If you normally eat 3,000 calories/day, and cut it to 2,000 calories/day, you won't necessarily lose weight -- many people's metabolisms will simply slow down equivalently.
Happy for this guy that it worked, but not all of us are so lucky. Turns out there are a lot of different factors that affect our metabolism, which can be just as important (if not more).
Edit: see Gary Taubes' work on this, extremely detailed stuff on what regulates metabolism and fat storage, there's nothing simple about it -- e.g. https://www.amazon.com/Good-Calories-Bad-Controversial-Scien...