If all you're eating during the day is half of a sandwich would that still hurt your body like starvation would?

without enough calories per day your body can "starve". Pluse without the correct vitamins and minerals in your intake of food your body will begin to feed on itself to get what it needs. For example without enough calcium your body begins to leech it from your bones. If you are not eating the right vitamins and nutrients it could cause several problems ecspecially if you don't get enough protien(could cause loss of hair),potassium(leg cramps)and calcium (brittle bones) and so on.