Be careful about generalizing from one example.

I've read a fair number of accounts from people who were told repeatedly that there was a weight and/or calorie ration which would reliably improve their lives, but which didn't.

Kudos for the nutrition professor for not saying that what seemed to have worked for him (two months isn't a long run test, but he probably didn't feel like crap doing it-- some people would) isn't the solution for everyone.