Your body will get used to it - it's just complaining because it doesn't want to change!
You may know this, but in those 2800 calories, try to ensure that you are eating a lot of protein, and make sure your snacks are all high in fiber. The fiber slows down digestion which will mean you are less hungry, as well as your body getting a better shake at absorbing the good stuff you're eating, meaning less deficiencies.
A great snack for this is a cup of strawberries and cottage cheese. You get a sugar rush, fiber from the strawberries, and protein from the cottage cheese. These types of volume snacks with relatively low calories are key to me in dieting. I seek foods that give me nutrition that I can eat a lot of.
Another example is a spinach salad. You can basically eat a whole bag of spinach if you want. Eat as big a portion as you can with only 2tbls of dressing shaken to evenly coat. Sprinkle some almonds or brazil nuts on for even more protein.
It's these kind of snacks which will help you a lot more than sugary granola bars or some of these other "smart" snacks. Real food is important if you only get 2,800 - it means the 2,800 has to be good stuff.
Don't know if this helps - hope it did.