@Frankieola
Is "800" a typo and you meant 1,800?
Less than half standard calories will almost certainly mean vitamin deficiencies, unless you take supplements (the marketing people love that) and starvation diets put the body into "emergency metabolism" mode, whereby muscle glycogen stores, then actual muscle fibre bulk is broken down. (Glycogen is long chains of glucose whereas proteins are broken into amino acids, then the amino part is stripped off, leaving molecules which feed into carbohydrate metabolism, all to maintain supply of glucose to the brain).
This page
http://www.m.webmd.com/diabetes/type-2-diabetes-guide/reversing-type-2-diabetes
(select "Stay on US site" at the prompt)
says a combination of diet and exercise are required.
This is a permanent lifestyle change, as far as I can make out. Fat cells become "fatigued" from responding to high insulin level and is either permanent or takes as many years of reduced insulin levels to reverse it as it took to provoke it. To a certain extent, genes respond to their chemical environment, in the same way a supermarket adds increases staff on the tills, when a crowd of shoppers turns up. This is expensive, so the manager 'fine tunes' how many extra staff to add. By analogy, the fat cell has the job of turning excess blood sugars into fat but building the enzyme "machinery", to do this, uses up "expensive" resources and DNA got where it is today by not being wasteful of energy and scarce resources.