Any weight loss is a plus. As a bicycle rep once told me: "How low do you want to go? It's only $$" . But it's a LOT easier to lose weight from you than the bike and you save money losing it on you. Eat less, it costs you less. Buy light-weight components and it costs you a LOT. For me it would only make sense to lose the weight from me until I reach the healthy minimum I should be, THEN cut weight on the bike. But if I had the $$ I'd certainly buy the lightest bike I could afford(which isn't the case).
When it comes down to it, the ultimate choice is your's.
But to answer your question, yes it would help.