An MIT-trained physicist should know the common name for a unit of energy. Sure, he might not remember the conversion from joules to calories, but to have never heard of it?

That's taking a literal reading ("I didn't know what a calorie was"), but perhaps he was referring to a more nuanced understanding ("I didn't understand how energy was used by the body"). That interpretation wasn't clear from the text though -- it seemed an overwrought attempt to portray an "Aw shucks, I didn't know what I was doing!" attitude.