The reason I am hungry is because I did not eat lunch.
This sentence contains a redundancy. "Because" is a conjunction that means "for the reason that." It is not necessary to have two words that the convey the same meaning in one sentence. Replace "because" with its definition to illustrate the redundancy.
The reason I am hungry is for the reason that I did not eat lunch.
To correct the original sentence, either replace "because" with "that" or remove both "the reason" and "is."
The reason I am hungry is that I did not eat lunch.
or
I am hungry because I did not eat lunch.
Remember never to use "reason" and "because" together in a sentence.
