During World War II, Ancel Keys and his colleagues at the University of Minnesota conducted a landmark study in human nutrition and hunger: the Human Starvation Study.
Keys sought to answer questions that were being raised by the horrible conditions brought about by the war in Europe: the effects of extremely low-calorie diets and cold, for example. The experiences of the participants in the semi-starvation conditions brought to light the psychological effects of hunger, particularly an inability to focus on anything other than food (including sexual relationships and intellectual persuits). His work is usually discussed in relation to Maslow's Hierarchy of Needs because the subjects behavior seems to support the idea of the primacy of physiological needs.
Another fun fact: the "K-ration" developed for the US Army is referred to as such because of Keys' role in creating it (K for Keys).