Caloric Restriction: Difference between revisions

The hormonal and metabolic effects of calorie restriction observed in experimental animals, such as lower body temperature, reduced metabolic rate, and decreased oxidative stress, have also been demonstrated in humans.{{pmid|18729811}}{{pmid|16595757}} Additionally, lower serum levels of basal insulin ("fasting insulin"), profibrotic proteins, various growth factors - such as PDGF and TGF-α - as well as cytokines like Tumor Necrosis Factor-α have been detected.{{pmid|15096581}}{{pmid|17389710}}{{pmid|17093155}}{{pmid|16732018}}{{pmid|16412867}} It is also established that long-term calorie restriction is an effective prevention against Type II Diabetes, high blood pressure, and Atherosclerosis, which together are the main causes of Morbidity, disabilities, and Mortality in humans.{{pmid|19262201}}

Currently, there is no scientific evidence that permanent calorie restriction – with adequate nutrition – leads to an extension of life expectancy compared to a lean adult.<ref>{{cite web |author=Stephan Schleim |url=https://www.heise.de/tp/features/Auf-der-Suche-nach-dem-Jungbrunnen-das-Beispiel-Kalorienreduktion-3395506.html |title=In Search of the Fountain of Youth: The Example of Calorie Restriction |website=[[Telepolis|heise.de]] |date=2012-08-31 |access-date=2015-05-11}}</ref> It is undisputed that severe overweight, i.e., obesity, leads to a reduction in average and maximum life expectancy. However, reviews have confirmed that calorie restriction (or [[Intermittent Fasting|Intermittent fasting]]) in healthy adults is likely to lead to similar life extension – extensions of health and lifespan – as observed in animal experiments. They describe the health effects and molecular mechanisms of such phases, including Autophagy. A problem with scientific studies on this is that the relatively long lifespan of humans makes it difficult to directly test such interventions.{{pmid|34518687}} Periods in which calorie intake is limited to a constant deficit can be combined with intermittent fasting (periods with intervals of consuming no food, only water, and tea/coffee, for example) and variants of the Mediterranean diet, which typically have long-term cardiovascular benefits and could also increase longevity.{{pmid|32943166}} Which protocols (such as duration and magnitude of the calorie deficit) and combinations (see, for example, Caloric restriction mimetic, effects of coffee, and AMPK) with calorie restriction are effective or most effective in humans in general and depending on the individual{{pmid|34555343}} is still unknown.

Specifically in the USA, the results of animal experiments have led to many practitioners adopting calorie restriction, particularly in California. A group of these practitioners formed the ''Calorie Restriction Society''. Excessive calorie reduction always carries the risk of malnutrition, which can negatively affect physical and mental health. There are repeated warnings about potential eating disorders with calorie restriction. On the other hand, a study showed that calorie restriction does not lead to an increase in anorexia or bulimia. The psychological effects of calorie restriction were evaluated as positive in this study.{{pmid|18248104}}

Long-term undernutrition can, besides positive effects, also lead to various deficiency diseases. Developmental disorders can occur in minors. Cold sensitivity may increase.{{pmid|19944269}} Ovulation can be suspended in women with very low BMI, resulting in temporary infertility.{{pmid|19944269}} In the ''Minnesota Starvation Experiment'', anemia, edema in the lower extremities, muscle wasting, weakness, neurological impairments, dizziness, irritability, lethargy, and depression were observed in adult males undergoing a six-month calorie restriction with a 90% carbohydrate diet.<ref>{{cite book|last1=Keys|first1=A.|last2=Brozek|first2=J.|last3=Henschels|first3=A.|last4=Mickelsen|first4=O.|last5=Taylor|first5=H.|title=The Biology of Human Starvation|year=1950|volume=2|publisher=University of Minnesota Press|location=Minneapolis|page=1133}}</ref> Short-term calorie restriction can lead to muscle wasting and reduced bone density.{{pmid|19851100}} In individuals with low body fat, calorie restriction can be harmful.{{pmid|17341713}}