If there's anyone who likes this, I'm not kink-shaming. However. Can you please elaborate on what exactly it is that makes your dick hard? Do you imagine a woman literally gaining weight while she's eating on your lap? I'm genuinely trying to understand and looking for serious responses.
I can find an explanation for all sorts of fetishes, but I have no idea what part of -flails hands- whatever this is can make a penis erect. If you're ashamed to disclose the reasons, reach out to me and tell me privately. I'm just curious.