In November of 1944, Physiologist Ancel Keys and some colleagues at the University of Minnesota conducted a fascinating study known as The Minnesota Experiment.
It consisted of 36 healthy anti-war young males in good mental and physical health who were put on starvation diets to the point of losing a quarter of their body weight, and then refed.
Although the original intent was to examine how starvation, and subsequent refeeding, affected World War II soldiers, this study shed fascinating light on what happens on semi-starvation diets.
For the first 3 months, participants consumed 3,200 - 3,500 calories a day (the amount needed to maintain their weight at the time), eventually cutting down to 1800.
The last 3 months, men were assigned different caloric levels to observe what changes the body undergoes during refeeding.
Keep in mind that throughout the entire study, regardless of how many calories they were taking in, the men burned approximately 3,000 calories a day.
By the way, when these men significantly cut their caloric intake -- resulting in losing a quarter of their body weight, as evidenced by photos in which their ribcages stick out -- their diet consisted mainly of carbohydrates, including white bread, potatoes, and jello.
I would love to hear how Gary Taubes and his fervent low-carb supporters explain this within their framework of "carbohydrates make you fat, calories are irrelevant, and exercise has nothing to do with weight loss."
Anyhow, back to reality.
The results of The Minnesota Experiment were published in 1950 in a 1,385-page tome titled The Biology of Human Starvation.
It clearly demonstrates the immense psychical and psychological toll that starvation diets took on these men.
Anemia, edema, dizziness, guilt, self-inflicted harm, shoplifting, loss of sex drive, and "semi-starvation neurosis" were experienced pretty much across the board.
The more repressed food was, the more it was on these men's minds, to the point of unhealthy obsession.
It took at least a year for most of the participants to truly feel physically and psychologically recovered.
For more information on this fascinating study, I highly recommend reading this summary.