My quite particular DS12 (5'4 stocky/broad build, not very active) eats for Britain and currently has on an average day a combo of...
Breakfast
6-10 weetabix and a pint of milk OR two bowls porridge OR boiled eggs and toast, all plus a banana and maybe a yoghurt, glass of juice
Mid morning snack
Flapjack OR hot cross bun, fruit, yoghurt etc
Lunch
Two egg omlette (ham,cheese, toms) OR
2 x tuna rolls and crisps/salad bits OR a large bowl soup and a ham/cheese sarnie, OR a four fish finger sarnie and salad bits OR a large jacket pot with prawns cheese and beans (random combo I know), OR bowl of tuna sweetcorn pasta plus a piece of fruit for pudding
After school snacks
Toast and jam, crumpets and honey, carrots/cucumber/breadsticks and hummous, whole box of grapes, even more yoghurt, soreen loaf and butter, popcorn, chunks of cheese
Dinner (always a full large adult portion)
Fish, chips, peas and broccoli OR chicken curry rice and naan, OR four sausages, mash, green beans, brocc, carrots OR lasagne chips salad bits garlic bread OR gnocchi bake with pancetta, courgettes, peppers, muchrooms OR three large fajita wraps with chicken and prawns
Puddings (most evenings)
Yoghurt, fresh fruit salad, pancakes, sorbet/ice cream, crumble, trifle, fruit cake etc
Extra peckish?
Yet more toast, cheese, yoghurt and fruit or cereal
If left to his own devices he'd load up on carbs/cake/bread products and he'll only eat eggs/meat in certain formats and scenarios but he also eats most veg, loves fish/seafood so it sort of balances out. He is genuinely hungry enough to eat all that and isn't overweight so we just keep throwing it at him till he says he's full! God knows how we'd manage without yoghurt!