In terms of health and fitness? You can't go far wrong with oats or eggs. Oats are quite nutrient dense, high in fibre and protein and will keep you feeling full. Eggs are very nutrient dense and high in protein.
For breakfast, I personally go with:
1) Porridge oats cooked in the microwave with half water, half milk, a chopped banana, ginger and honey
2) Dry oats mixed with cold yoghurt, chopped banana, frozen berries, whey protein powder
3) Two or three eggs, put in boiling water for about five minutes from the fridge so the yolks are still soft, and a couple of slices of toast
4) As a treat, a ham and cheese croissant done in the oven
5) For weekends where I have no plans other than to eat until midday, I'll make a bacon and egg fry-up or thin pancakes with grated cheese and ham
If all else fails or I'm pushed for time, a cup of coffee and a piece of fruit will get me by.
Coffee and a cig has served me well for the best part of the last decade. I started putting on a bit of tub when I switched the fags out for a vape though, so if you want to stay lean stick to the Marlboros, is all I'll say.
Lass I know is a nutritionist and swears by oats. Apparently you should do them with salt and if you want flavour, peanut butter is one of the most nutrient dense things you can have. (Proper peanut butter mind, not the stuff they put in Reeses cups.) She's also an anti-vaxxer and reckons dairy gives you depression, though, so I'm not sure how much of her expertise actually veers into quack territory.
Come to think of it I don't think I've ever met a food/health expert who didn't have at least one slightly mental belief to make you question the rest of their qualification.
The problem with giving nutritional advice is the same as in public health generally, there's pitfalls in applying population level data to individuals. Biology is so complex and there are so many mechanisms at play that we use blunt statistical tools to say, "this seemed to work this way on average for most people", but of course that's only a first approximation and a lot more needs to be done for the person in front of you.
Another issue is that some people then people make the opposite error, and conclude that if something has adversely affected them and/or a select few cases, then it must not be good for anyone. For example, you have people that swear by meat only diets, when in reality they've probably unknowingly eliminated some allergen that bothers them but most other people can tolerate pretty well.
Understanding this is one of the key differences between being a good and bad practitioner (of anything related to health, dietician, physio, etc.), in my opinion.
