RE: Dr. Weltzin's statement of, “And if you’re eating that little and maintaining your same level of fitness, that’s a problem.”
I'd like to see some science to back this up. How is that even a problem? I eat proportionately less than the example given (200 pounds, ~10%, & about 2,200 calories a day) and I've had no problem maintaining my weight and increasing my maxes as I get ready to compete at nationals for powerlifting next month. The body is not a textbook and we don't all have the same caloric requirements. I'm so tired of seeing this dogma repeated by both the scientific community who are all theory & no practice and the fitness community who blindly follow the broscience of other members.
The only person who can tell you what's best for your body is you. Take the time to figure out what macro split works best for you, what your optimal level of caloric intake is, etc., by trial and error, not by reading what others say, and it'll be much easier to reach your goals.