Much of Britain's food came from other countries in ships. Enemy submarines sank so many ships that there was a shortage of some foods. Rationing, which started in 1940, made sure everyone got a fair share. You had to hand over coupons from your ration book, as well as money, when you went shopping. When you had used up your ration of one food (say, cheese or meat), you could not buy any more that week.
Many people grew vegetables at home or on allotments. Children helped 'Dig for Victory' by digging, planting and weeding., and working on farms.
Some families kept chickens, ducks and rabbits (to eat). People started 'Pig Clubs', collecting food leftovers in pig bins to feed the pigs. There were plenty of potatoes and carrots, and lots of suggestions for new ways to cook them! 'Potato Pete' and 'Doctor Carrot' advertised these foods, to encourage people to eat more of them.