If the president never eats in public, how do we know they’re not a robot? This was a major plot point in the Asimov short story Evidence. The character went to extreme lengths to avoid being seen eating (and turned out to be a robot in the end).

How do you know anyone isn’t a robot who can fake eat?

This is the premise of the short story. The robot politician pretends to eat in order to trick his opponents who are trying to out him as a robot by proving he can’t eat.

Spoilers: they then try to trick the robot into violating the three laws of robotics. He ends up tricking his opponents by having another robot attack him, letting him freely defend himself when he otherwise wouldn’t be able to (since robots can’t harm humans).

It’s a fantastic story. Well worth the read. My description doesn’t do it justice.