Will I lose weight cycling 12 miles a day?

I'm curious, is it realistic to expect significant weight loss by cycling 12 miles per day? I understand exercise is key, but does the distance and activity alone guarantee weight reduction? Could there be other factors, such as diet or lifestyle habits, that could hinder progress? And how long should I expect to maintain this routine to start seeing results? I'm eager to learn how cycling fits into an overall weight loss plan.