Not enough calorie intake?

try adding more fat/protein into your meals. they have a higher caloric density for small servings. maybe add nuts or whole milk to your cereal? try ensures/boost/other drinks to get your nutritional needs if it is really that hard to feel hungry.

If this is just one day, it's ok to be underfed occasionally. However, if this is an example of a typical day, you need to add more calorie dense foods like protein and healthy fat (nuts, seeds, avocado, olives, etc). Don't eat enough spinach to fill up. Have something else with more calories with it.

Just because you dont feel hungry doesnt mean you should starve yourself, Your body needs the nutrients in so many ways that I cannot tell you. Eating less then 800 calories is very dangerous and will definitely put you in the ER within weeks. DONT do it. Eat when you know it time to eat. Ex if it been more then standard 4 hours without meal, start eating again. Your body is going on a slow metabolism so obviously you will get hungry much later then usual but again you still have to eat. Dont attempt to starve yourself, your only slowly killing yourself that way

I eat 750 calories before 6 am most days and I'm 190, and about 12% body fat. Eat, good lord.

that is not good, very unhealthy, just like george, i eat over 900 for breakfast and i'm 165

NOBODY eats claories. That is only the ehat energy in the food itself.