A large amount of our data on the human body's response to starvation comes from one single study https://en.wikipedia.org/wiki/Minnesota_Starvation_Experiment
"The experiment was planned in cooperation with the Civilian Public Service (CPS) and the Selective Service System, using volunteers selected from the ranks of conscientious objectors who had been inducted into public wartime service. Ancel Keys obtained approval from the War Department to select participants from the CPS."
Even more intense, there's this book of observational research performed by Jewish doctors in the Warsaw Ghetto as they and their communities slowly starved to death.
https://theconversation.com/warsaw-ghettos-defiant-jewish-doctors-secretly-documented-the-medical-effects-of-nazi-starvation-policies-in-a-book-rediscovered-on-a-library-shelf-182726
"With final deportations of the few surviving Jews underway and his own death imminent, Milejkowski wrote of the dark, yawning emptiness of the ghetto at that moment, and the horrifying conditions the doctors had labored under to conduct and record the research."
Even more intense, there's this book of observational research performed by Jewish doctors in the Warsaw Ghetto as they and their communities slowly starved to death.
https://theconversation.com/warsaw-ghettos-defiant-jewish-doctors-secretly-documented-the-medical-effects-of-nazi-starvation-policies-in-a-book-rediscovered-on-a-library-shelf-182726