It's a little more complicated than mere heat. The thirst is a natural physiological response to, and symptom of poisoning, during which electrolytes are routinely leeched from the body causing dehydration to occur and persist for as long as active poisoning is sustained. A greater contributor to the fierce thirst is the constant taxing of the cardiovascular system, the reason for which many describe DNP use as mild 24-hour cardio. This continuous cardio (making it seem as though every task even walking is 1/3 harder) along with other poisoning effects elevates body temperature, and would do so fatally were it not for an adaptive type of physiological system sharing. Both the heat and workload generated by DNP is offset by the cardiovascular system onto the respiratory system, thereby increasing overall respiration (breathing) resulting in a constant drying of the upper GI tract (specifically the mouth and throat). This fascinatingly adaptive sharing capacity is very similar to the regular functioning of a canines cooling system, i.e. panting, which benefits the entire body by simultaneously reducing body temperature and blood pressure.