Calorie restriction (caloric restriction or energy restriction) is a dietary regimen that reduces the energy intake from foods and beverages without incurring malnutrition. The possible effect of calorie restriction on body weight management, longevity, and aging-associated diseases has been an active area of research.
Caloric intake control, and reduction for overweight individuals, is recommended by US dietary guidelines and science-based societies.
Calorie restriction is recommended for people with diabetes and prediabetes, in combination with physical exercise and a weight loss goal of 5-15% for diabetes and 7-10% for prediabetes to prevent progression to diabetes. Mild calorie restriction may be beneficial for pregnant women to reduce weight gain (without weight loss) and reduce perinatal risks for both the mother and child. For overweight or obese individuals, calorie restriction may improve health through weight loss, although a gradual weight regain of per year may occur.
The term "calorie restriction" as used in the study of aging refers to dietary regimens that reduce calorie intake without incurring malnutrition. 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. This study was conducted during World War II on a group of lean men, who restricted their calorie intake by 45% for six months and composed roughly 77% of their diet with carbohydrates. As expected, this malnutrition resulted in metabolic adaptations, such as decreased body fat, improved lipid profile, and decreased resting heart rate. The experiment also caused negative effects, such as anemia, edema, muscle wasting, weakness, dizziness, irritability, lethargy, and depression.
Typical low-calorie diets may not supply sufficient nutrient intake that is typically included in a calorie restriction diet.
People losing weight during calorie restriction risk developing side effects, such as cold sensitivity, menstrual irregularities, infertility, or hormonal changes.