Low calorie

Calorie restriction, or caloric restriction, or energy restriction, is a dietary regimen that reduces calorie intake without incurring malnutrition or a reduction in essential nutrients. "Low" can be defined relative to the subject's previous intake before intentionally restricting calories, or relative to an average person of similar body type. In a number of species, including yeast, fish, rodents and dogs, calorie restriction without malnutrition has been shown to slow the biological aging process, resulting in longer maintenance of youthful health and an increase in both median and maximum lifespan. However, the life-extending effect of calorie restriction is not shown to be universal.

In humans, the long-term health effects of moderate caloric restriction with sufficient nutrients are unknown.

Using rhesus monkeys – which harbor 93% of the human genome – a collaboration of the United States National Institute on Aging and the University of Wisconsin found that caloric restriction without malnutrition extended lifespan and delayed the onset of age-related disorders; older age, higher diet quality, and female gender were positive factors affecting the benefits realized from lower caloric intake.

In humans the long-term health effects of moderate caloric restriction with sufficient nutrients are unknown.

As noted above, the term "calorie restriction" as used in biogerontology 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 6 months, and composed roughly 90% of their diet with carbohydrates. As expected, this malnutrition resulted in many positive metabolic adaptations (e.g. decreased body fat, blood pressure, improved lipid profile, low serum T3 concentration, and decreased resting heart rate and whole-body resting energy expenditure), but also caused a wide range of negative effects, such as anemia, lower extremity edema, muscle wasting, weakness, neurological deficits, dizziness, irritability, lethargy, and depression.

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