He was probably talking about the fact that your body goes into "fat-burning" mode overnight, and the longer you stave off eating the longer your body uses fat for fuel.
If you are cool with that, fine.
As for our ancestors only eating lunch and dinner - complete BS. All evidence points to h/g eating in the morning (maybe leftovers from the night before, maybe something else) and then not eating again until dinner. A pot of stew would be left going all day for kids/pregnant/lactating/etc. people to have lunch if they were hungry. But the guys who went out hunting, and the women who went gathering(fishing) all day wouldn't carry a meal with them.