Person A argues that skipping breakfast has no effect on a person likelihood to gain weight.
Person B takes the position opposite that breakfast in fact curves hunger and chances of putting on weight.
Person A then asserts that they in fact hold no position on the issue and that Person B is arguing on a moot point
This then creates a fallacy that Person A's argument is invalid because they were arguing against a position that was not held and in doing so their character is brought to question, and through this the character of their argument is also questioned.
It's almost like an Ad hominem, but not quite. The tricky part is that Person A maintains they have no position, although they do.