Sometimes I get stuck in places or situations where I don't get to eat lunch or something else as planned. I carry a protein bar in my purse all the time. Then if I get tied up I can eat that so that I don't let myself get so hungry that I eat things I shouldn't or stuff myself.
My favorite protein bar is Pure Protein bars with 180 - 200 calories depending on flavor. It keeps my protein and carbs up and is easy to carry with me. I buy a box of them at Walmart in the pharmacy area. Some protein bars are higher in calories. Zone bars are also good.