No cake at baby shower

I take metformin at night but otherwise am completely diet controlled. To stay in range I prepare all of my own food and weigh and measure everything. It takes a lot of time and discipline and I am lucky diet alone works when most women can't control bs without meds by no fault of their own. But I still wish I could eat at my shower on Saturday. I don't want to come off rude either. I plan to eat before and try to be gracious and not whiny about not eating anything at shower... Any advice from women who have had to decline food at shower? I don't even want to nibble at the shower bc I won't be able to keep track of carbs and protein. Etiquette is important to me. Any advice is greatly appreciated!