About that “eye contact” thing . . . speaking as an experienced communicator and public speaker, it’s absolutely right on. Sustained eye contact can make people either fully engaged and listening, or uncomfortable—or both. And both, either separately or together, can help get you noticed and remembered.
Here’s a way to make it even more powerful: don’t blink until you absolutely have to. An unblinking stare really rivets people’s attention, and usually they don’t even know why. It shouts “authority” at a subliminal level.
As far as the nutrition “experts” are concerned, if they won’t take a tactful hint, I usually say something like, “Never argue nutrition with a diabetic. We know more about it than anyone else. We have to; our lives depend on it.” There’s a great deal of hyperbole and generalization in that statement, of course, but it usually does the job.