It was a study the U of M conducted to see how long the human body can sustain itself on half of the calories an average grown man needed, from 3,000 to 1,500 calories a day. http://www.apa.org/monitor/2013/10/hunger.aspx The reason this study was carried out was to aid in helping starving people live after sieges and bombings. I remember reading about the siege of Leningrad where people who weren't working in factories were given 600 grams of food and those who did work 300 or 700-1550 per day. I'm fairly certain no one in the US, both today and in the 40s, can imagine such rationing let alone the Tubblrinas today.