As an add on to my earlier response… Here are some ideas for carb options that we like in our home. We have a pack of kids of all ages plus plenty of bonus ones that get fed regularly and rather crazy schedules, so we do a lot of quick-assembly and make ahead things, need meals to be pretty customizable for individuals, and need to have backup options on hand.
-We use a rice cooker to make rice or similar grains (ours is a stainless steel model from Aroma (we avoid nonstick coatings) and since it’s electric we can let it cook unsupervised. Rice can sit for about 2 hours on the warm setting and then we dish out any leftovers into individual serving sized rectangles on plastic wrap, wrap up tightly, label & pop them in the freezer. They’ll last a month frozen and reheat quickly in the microwave with a little water added. If it’s stored in the fridge it’ll last 1-2 days. In addition to white rice try brown rice, farro, barley, lentils and couscous.
-Pasta. We always have pasta on hand with at least some butter and Parmesan, and that means we have extra carbs available within 10 minutes. Heat the water in your electric kettle then transfer to a sauce pan with pasta to speed it up.
-When we use the oven we almost always add in an extra pan of diced potatoes (white, sweet or a combination) and a few links of sausage to roast. This goes in the fridge as a base for breakfasts (toss in skillet to reheat, add eggs) or as quick adds to meals. Either do a small dice or poach larger cubes first so they cook quickly & evenly in the oven.
-Bags of frozen rolls that can be individually baked in the number you need.
-Frozen chips.
-Make a double serving of mash for dinner early in the week so you have leftovers to reheat (add some extra liquid). We do the same with potato salad and pasta salad (no reheating necessary for those). We also keep pouches of instant mashed potatoes in the cupboard for starving teen “emergencies.”
-Try out different freezer meal options to find ones he likes that you can keep on hand. Look for heavier things like Mac n’cheese, burritos, lasagne, personal sized pizzas, etc. It doesn’t have to be enough for a whole meal in itself since there’s additional dinner available, but sometimes he may just need the equivalent of two dinners.
-If he’s willing to be a little adventurous by UK standards, see if you can find a brand of frozen tamales he likes. These are a go-to in my house since I grew up with them. We stick a bag in the fridge to defrost and then they can be steamed on the stove or microwave 2-3 at a time. They’re little packages of dense carbs, fat & protein
-Batch cook hearty things like savory beans and stews, then freeze 2-3 portions in smallish glass containers that can be transferred into a saucepan for quick heating. Can be eaten with rice to add even more carbs.
Quick pre-dinner or post-dinner grabs for starving family members that aren’t crisps (which are also fine):
-Cheese and sausage cubes, or just cheese sticks. We go through a silly amount of cheese.
-Boiled eggs
-Full fat yogurts
-Jerky & meat sticks
-Crackers and hummus or a creamy dip
Also, we started making a pot of porridge at breakfast a while back and it’s actually helped immensely with everyone feeling better and less hangry in the afternoon/evening. We use our rice cooker for this so no one has to stand over a stove. Since he gets up early you could dish a good serving into a bowl, put some butter slices and brown sugar on top, and cover tightly. He can just add some milk & microwave in the morning. Egg muffins full of meat & cheese are another breakfast go-to for us; they often get microwaved and wrapped in a paper towel on the way out the door.