Final answer:
The most unexpected effect of starvation in the Minnesota Study was the severe psychological impact, including the development of obsessive behaviors around food and significant emotional disturbances. These effects persisted even after resumption of normal eating.
Step-by-step explanation:
The Minnesota Starvation Experiment, conducted during and shortly after World War II, unveiled numerous effects of starvation, but one of the most unexpected outcomes was the psychological impact, particularly the development of obsessive behavior around food. Participants experienced severe emotional and cognitive changes, which included depression, hysteria, and hypochondriasis, as they became preoccupied with food, collecting recipes, and even eating inedible substances. Moreover, the study revealed that prolonged fasting significantly reduced metabolic rate as an adaptive mechanism to energy scarcity, which could have lasting consequences on bodily functions and overall health.
Although weight loss, fatigue, and muscle tissue breakdown were anticipated, the extent of the psychological and behavioral changes were quite surprising. These changes persisted long after the period of refeeding commenced, suggesting that the effects of starvation could extend far beyond the immediate physiological needs for energy and nutrient intake.
In response to the low glucose levels, hormonal changes occur; levels of glucagon increase to mobilize glucose from reserves, while insulin secretion decreases. The adrenal glands release cortisol and epinephrine to maintain glucose supply to vital organs, which is one of the body's critical responses to extreme starvation.