My food rules, with 3 x DC's, 2 of whom had health issues. They are now all over 6 foot tall adults with their own lives.
No snacks between getting up for breakfast and after school. They had access to a big breakfast, a big lunch and a small snack, ie a piece of fruit after school. No restriction on water or juice. Then an evening meal.
They never had to eat the whole plate, but knew there would be nothing else until the next meal.
Breakfast would be either porridge, bacon and eggs with wholemeal toast, poached egg with wholemeal toast or yoghurt.
Lunch would be a sandwich, 2 slices of wholemeal with meat or egg, plus a yoghurt, plus crisps and a treat that might be a granola bar or a cereal bar.
Snack on the way home, a banana, orange, apple, rarlely a cereal bar at the end of the week.
Dinner - Meat, carb and veg combo, could be Veg, italian, Asian, UK, European, etc. You get the picture, I cook every night for my benefit as a downtime for me, but the family benefit.
So, food rules are, you eat 3 x times a day. You think about snacks. You eat a good evening meal.