Psychodad -
Basically, DNP inhibits the breakdown of ADP which precedes the production of ATP (Kreb's/electron transport chain etc.). Now, ATP is the form in which energy is stored, and importantly, utilised by our bodies and, when it can't be made, will result in the emittance of heat (in any system, heat is the simplest form via which energy can be, and frequently is, lost. e.g. light bulbs) as the energy is wasted.
So, ATP production is decreased by DNP which means the body has little energy to utilise for day to day activities resulting in the lethargy you will feel. Heat is produced and lost via radiation.
DNP is fat soluble meaning that as you begin loading it will tend to accumulate in your fat cells. ATP is required by fat cells for fatty acid synthesis as well as general survival. By disallowing ATP synthesis your body is forced into relying on previously stored energy reserves. Hence fat burning for fuel by adipocytes (the body's fat cells which store fat).
To summarise, DNP causes the body to waste energy forcing it to rely on stored fuel. Luckily, it tends to accumulate in adipocytes due to it's fat solubility and so that's where it carries out most of it's work.
Thus, I don't really think it will matter much what you eat. Obviously, your body won't be completely saturated with DNP (if it is...you know the score) so you're body will still survive and be able to carry out all important functions as well as store some ATP and fats (though any fats you ingest will be more readily burned for fuel since they will be in your blood stream more readily than stored fats). It's just a case of dieting as you usually would to prevent fat gain or increase fat loss.
With regards to the carbs, less in your system would no doubt encourage fat burning but not necessarily due to the DNP and not necessarily that much faster (since not every cell in your body is saturated with the DNP. Increasing dose increases saturation in turn increasing fat burning - but also increasing likelihood of death due to lack of ATP for simple cell function). Complex carbs, as stated by Heretic, will need to be broken down into glucose before glycolysis can occur. Complex carbs = more glucose = more energy waste = more heat = more suffering.
Simple carbs mean more energy (remember - not all cells are saturated so some will produce ATP the normal way) and more energy waste/heat but you will feel tired enough on the DNP so why make yourself feel more miserable? Simple carbs will keep you going. Chocolate works too (but contains fat). If you can handle the lethargy and really want maximum fat loss I should think that it would be more efficacious to stick to low carb although i don't think the difference would be that drastic from a higher carb one as the cells which don't have the DNP will preferentially turn to glycogen stores in the liver for glucose anyway if none is present in diet and so won't turn to fat until stores are exhausted. At which point they will also be eating up precious muscle for energy. Hence, i think low carb will result in, sure greater fat loss, but also probably greater muscle loss.
Sorry for the long-winded approach but I wanted to explain my reasoning.
I stuck to eggs (no yolk), toast and beans in the morning (unless training in which case empty stomach) and a large bowl of fruit for lunch. Dinner was something low fat with lots of veggies and chicken usually. I tried pasta once!!!!!!
Hope this helps.