I didn't see it that way. When people want to make fun of ridiculous claims, they usually make over the top comments that are dripping with sarcasm. I know because I have a tendency to write like that.

Humor, that’s actually funny, uses a well recognized trait or characteristic and exaggerates it. We recognize it in ourselves or others, and that's why we laugh. Sometimes it makes us a little uncomfortable because it hits so close to the mark. Sometimes it crosses the line into mean-spiritedness and it's not longer funny at all. Other times it completely misses the mark.

I believe this is the latter case. He is describing a behavior that we simply haven't observed. Well actually if we have observed it, it's in the case of someone following a low-fat, low calorie diet that's either borderline or downright anorexic. In fact, it’s almost as if he was making fun of anorexia. If anything, people who loose weight through low-carbing are all the opposite of what he says.

So that's what makes it un-funny. It's as if he was joking about how African Americans talk in a high-pitched nasal voice. No one would get the joke because that's simply not a common characteristic.