Make a stir-fry a day before or a poké bowl and take it to work. With salads, quiches and co. there’s a risk of overdoing the oily parts (sauces, cheese) and people end up eating “healthy” 1000 calories-worth meals.
I measure oil for my stir-fries with a spoon and one tablespoon is enough for a meal of 5-6 portions. I always prioritise vegetables and add many different ones, then protein and rice/noodles. There are tons of different noodles on the market and I love trying them all because I don’t eat gluten.
Have a lunch box/container for 350-400 grams of food. It’s a normal-sized portion. I have glass ones with plastic lids that take microwaving and freezing.
Snack only when hungry and recognise the time that you are most likely to be hungry. I find it difficult to survive without food between lunch and dinner, and this is quite normal - it’s normal to get hungry after a couple of hours when you’re active and it’s 7h or more between meals. Have a healthy snack - a large banana, a very small amount of nuts or a couple of rice balls (I make them home and wrap in seaweed sheets). If nothing else works have a protein bar or a nut/oat bar, as long as they are around 200 kcal.
Rice cooker has been the best investment in my household, I cook brown rice, long grain, jasmine, basmati, short grain, all pulses (soy, lentils, beans) and porridge in the rice cooker.