Food prices have gone up significantly over the last few years. For many people, this means having to eat more cheaply. You can still have a good, varied diet on a budget and the British Dietetic Association has some brilliant ideas for reducing food costs while maintaining a healthy diet. https://www.bda.uk.com/resource/food-facts-eat-well-spend-less.html
How do we know whether we’re eating the right amounts of the right foods? The British Nutrition Foundation has a handy guide to portion sizes, and rather than concentrating on weighing and measuring, it uses easy-to-compare measurements, such as a baked potato the size of your fist being a portion. https://www.nutrition.org.uk/putting-it-into-practice/balancing-the-diet/get-portion-wise/