Try going to the supermarket on foot and with just a backpack. This way you limit yourself to buy only the things you really need. Just try it! It is an experience to see the weight of your food intake.
Do not be scared, probably you have enough food in your pantry or freezer to live on for weeks.
I carried 14 kilos of food (31 pounds) the 3.6 kilometers (2.2 miles) to my home. I felt like a prehistoric gatherer getting the stuff home. It might just feed 5 people a week, but I sure did not buy snacks and had a great workout!