[1] If a restricted diet is not designed to include essential nutrients, malnutrition may result in serious deleterious effects, as shown in the Minnesota Starvation Experiment.
[13] This study was conducted during World War II on a group of lean men, who restricted their calorie intake by 45%[14] for six months and composed roughly 77% of their diet with carbohydrates.
[15][16][17] People losing weight during calorie restriction risk developing side effects, such as cold sensitivity, menstrual irregularities, infertility, or hormonal changes.
[1] Moderate amounts of calorie restriction may have harmful effects on certain population groups, such as lean people with low body fat.
[20] The Minnesota Starvation Experiment examined the physical and psychological effects of extreme calorie restriction on 32 young and lean 24-year-old men during a 40% reduction in energy intake for 6 months.
Despite the extreme calorie restriction, the experiment was not representative of true calorie-restrictive diets, which adhere to intake guidelines for macronutrients and micronutrients.
[21] Chronic weakness, decreased aerobic capacity, and painful lower limb edema was caused by the malnourished calorie restrictive diet.
[21][22] Emotional distress, confusion, apathy, depression, hysteria, hypochondriasis, suicidal thoughts, and loss of sex drive were among the abnormal psychological behaviors that occurred within six weeks.