Calorie restriction

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Calorie restriction (caloric restriction or energy restriction) is a dietary regimen that reduces the energy intake from foods and beverages without incurring malnutrition. [1] [2] The possible effect of calorie restriction on body weight management, longevity, and aging-associated diseases has been an active area of research. [1]

Contents

Dietary guidelines

Caloric intake control, and reduction for overweight individuals, is recommended by US dietary guidelines and science-based societies. [3] [4] [5] [6] [7] [8]

Calorie restriction is recommended for people with diabetes [9] [10] and prediabetes, [10] 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. [10] 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. [11] [12] For overweight or obese individuals, calorie restriction may improve health through weight loss, although a gradual weight regain of 1–2 kg (2.2–4.4 lb) per year may occur. [4] [6]

Risks of malnutrition

The term "calorie restriction" as used in the study of aging refers to dietary regimens that reduce calorie intake without incurring malnutrition. [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. [13] 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. [13]

Typical low-calorie diets may not supply sufficient nutrient intake that is typically included in a calorie restriction diet. [15] [16] [17]

Possible side effects

People losing weight during calorie restriction risk developing side effects, such as cold sensitivity, menstrual irregularities, infertility, or hormonal changes. [18]

Research

More research, both in humans and in experimental animals, is required to fully understand the connections between single nutrient modifications, calorie restrictions, and regular exercise in the prevention of CVD, cancer, cognitive deficit, inflammatory diseases, sarcopenia, and immune senescence. [1] [19] As of 2021, there is a lack of adequately controlled long-term studies examining the impact of calorie restriction in humans. [1] Although calorie restriction has the advantage of slowing down the reduction of muscle mass with age, the initial reduction of mass may be substantial and have an effect on a person's strength and endurance. [19]

Humans

Decreasing caloric intake by 20-30%, while fulfilling nutrient requirements, has been found to remedy diseases of aging, including cancer, cardiovascular disease, dementia, and diabetes in humans, and result in an average loss of 7.9 kilograms (17 lb) in body weight, but because of the long lifespan of humans, evidence that calorie restriction could prevent age-related disease in humans remains under preliminary research. [1] [20] While calorie restriction leads to weight and fat loss, the precise amount of calorie intake and associated fat mass for optimal health in humans is not known. [1] Moderate amounts of calorie restriction may have harmful effects on certain population groups, such as lean people with low body fat. [1]

Life extension

As of 2021, intermittent fasting and calorie restriction remain under preliminary research to assess the possible effects on disease burden and increased lifespan during aging, although the relative risks associated with long-term fasting or calorie restriction remain undetermined. [1]

Intermittent fasting refers to periods with intervals during which no food but only clear fluids are ingested – such as a period of daily time-restricted eating with a window of 8 to 12 hours for any caloric intake – and could be combined with overall calorie restriction and variants of the Mediterranean diet which may contribute to long-term cardiovascular health and longevity. [21]

Minnesota Starvation Experiment

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. The study was designed to mimic dietary conditions during World War II. Participants could only eat 1800 kcal per day, but were required to walk 5 km per day and expend 3000 calories. [22] The men lost about 25% of their body weight of which 67% was fat mass and 17% fat-free mass. [22] The quality of the diet was insufficient to accurately represent the diet during war due to the inadequate consumption of protein, and a lack of fruits and vegetables. Despite the extreme calorie restriction, the experiment was not representative of true calorie-restrictive diets, which adhere to intake guidelines for macronutrients and micronutrients. [22] Chronic weakness, decreased aerobic capacity, and painful lower limb edema was caused by the malnourished calorie restrictive diet. [22] [23] 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. [22]

Intensive care

As of 2019, current clinical guidelines recommend that hospitals ensure that the patients get fed with 80–100% of energy expenditure, the normocaloric feeding. A systematic review investigated whether people in intensive care units have different outcomes with normocaloric feeding or hypocaloric feeding, and found no difference. [24] However, a comment criticized the inadequate control of protein intake, and raised concerns that hypocaloric feeding safety should be further assessed with underweight critically ill people. [25]

Non-human primates

A calorie restriction study started in 1987 by the National Institute on Aging showed that calorie restriction did not extend years of life or reduce age-related deaths in non-obese rhesus macaques. [26] It did improve certain measures of health, however. [27] These results were publicized as being different from the Wisconsin rhesus macaque calorie restriction study, which also started in 1987 and showed an increase in the lifespan of rhesus macaques following calorie restriction. [26]

In a 2017 report on rhesus monkeys, caloric restriction in the presence of adequate nutrition was effective in delaying the effects of aging. [28] [29] Older age of onset, female sex, lower body weight and fat mass, reduced food intake, diet quality, and lower fasting blood glucose levels were factors associated with fewer disorders of aging and with improved survival rates. [28] Specifically, reduced food intake was beneficial in adult and older primates, but not in younger monkeys. [28] The study indicated that caloric restriction provided health benefits with fewer age-related disorders in elderly monkeys and, because rhesus monkeys are genetically similar to humans, the benefits and mechanisms of caloric restriction may apply to human health during aging. [30] [31]

Activity levels

Calorie restriction preserves muscle tissue in nonhuman primates [32] [33] and rodents. [34] Muscle tissue grows when stimulated, so it has been suggested that the calorie-restricted test animals exercised more than their companions on higher calories, perhaps because animals enter a foraging state during calorie restriction. However, studies show that overall activity levels are no higher in calorie restriction than ad libitum animals in youth. [35]

Sirtuin-mediated mechanism

Preliminary research indicates that sirtuins are activated by fasting and serve as "energy sensors" during metabolism. [36] Sirtuins, specifically Sir2 (found in yeast) have been implicated in the aging of yeast, [37] and are a class of highly conserved, NAD+-dependent histone deacetylase enzymes. [38] Sir2 homologs have been identified in a wide range of organisms from bacteria to humans. [37] [39]

See also

Related Research Articles

Dieting is the practice of eating food in a regulated way to decrease, maintain, or increase body weight, or to prevent and treat diseases such as diabetes and obesity. As weight loss depends on calorie intake, different kinds of calorie-reduced diets, such as those emphasising particular macronutrients, have been shown to be no more effective than one another. As weight regain is common, diet success is best predicted by long-term adherence. Regardless, the outcome of a diet can vary widely depending on the individual.

<span class="mw-page-title-main">Weight loss</span> Reduction of the total body mass

Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, by a mean loss of fluid, body fat, or lean mass. Weight loss can either occur unintentionally because of malnourishment or an underlying disease, or from a conscious effort to improve an actual or perceived overweight or obese state. "Unexplained" weight loss that is not caused by reduction in calorific intake or increase in exercise is called cachexia and may be a symptom of a serious medical condition.

<span class="mw-page-title-main">Fad diet</span> Popular diet with claims not supported by science

A fad diet is a diet that is popular, generally only for a short time, similar to fads in fashion, without being a standard scientific dietary recommendation, and often making unreasonable claims for fast weight loss or health improvements; as such is often considered a type of pseudoscientific diet. Fad diets are usually not supported by clinical research and their health recommendations are not peer-reviewed, thus they often make unsubstantiated statements about health and disease.

<span class="mw-page-title-main">Low-carbohydrate diet</span> Diets restricting carbohydrate consumption

Low-carbohydrate diets restrict carbohydrate consumption relative to the average diet. Foods high in carbohydrates are limited, and replaced with foods containing a higher percentage of fat and protein, as well as low carbohydrate foods.

<span class="mw-page-title-main">Okinawa diet</span> Eating habits of the indigenous people of the Ryukyu Islands

The Okinawa diet describes the traditional dietary practices of indigenous people of the Ryukyu Islands, which were claimed to have contributed to their relative longevity over a period of study in the 20th century.

A low-protein diet is a diet in which people decrease their intake of protein. A low-protein diet is used as a therapy for inherited metabolic disorders, such as phenylketonuria and homocystinuria, and can also be used to treat kidney or liver disease. Low protein consumption appears to reduce the risk of bone breakage, presumably through changes in calcium homeostasis. Consequently, there is no uniform definition of what constitutes low-protein, because the amount and composition of protein for an individual with phenylketonuria would differ substantially from one with homocystinuria or tyrosinemia.

<span class="mw-page-title-main">Healthy diet</span> Type of diet

A healthy diet is a diet that maintains or improves overall health. A healthy diet provides the body with essential nutrition: fluid, macronutrients such as protein, micronutrients such as vitamins, and adequate fibre and food energy.

<span class="mw-page-title-main">Protein–energy malnutrition</span> Medical condition

Protein–energy undernutrition (PEU), once called protein-energy malnutrition (PEM), is a form of malnutrition that is defined as a range of conditions arising from coincident lack of dietary protein and/or energy (calories) in varying proportions. The condition has mild, moderate, and severe degrees.

<span class="mw-page-title-main">Very-low-calorie diet</span> Diet with very or extremely low daily food energy consumption

A very-low-calorie diet (VLCD), also known as semistarvation diet and crash diet, is a type of diet with very or extremely low daily food energy consumption. VLCDs are defined as a diet of 800 kilocalories (3,300 kJ) per day or less. Modern medically supervised VLCDs use total meal replacements, with regulated formulations in Europe and Canada which contain the recommended daily requirements for vitamins, minerals, trace elements, fatty acids, protein and electrolyte balance. Carbohydrates may be entirely absent, or substituted for a portion of the protein; this choice has important metabolic effects. Medically supervised VLCDs have specific therapeutic applications for rapid weight loss, such as in morbid obesity or before a bariatric surgery, using formulated, nutritionally complete liquid meals containing 800 kilocalories or less per day for a maximum of 12 weeks.

A diabetic diet is a diet that is used by people with diabetes mellitus or high blood sugar to minimize symptoms and dangerous complications of long-term elevations in blood sugar.

Leonard Pershing Guarente is an American biologist best known for his research on life span extension in the budding yeast Saccharomyces cerevisiae, roundworms, and mice. He is a Novartis Professor of Biology at the Massachusetts Institute of Technology.

<span class="mw-page-title-main">Western pattern diet</span> Modern dietary pattern

The Western pattern diet is a modern dietary pattern that is generally characterized by high intakes of pre-packaged foods, refined grains, red meat, processed meat, high-sugar drinks, candy and sweets, fried foods, industrially produced animal products, butter and other high-fat dairy products, eggs, potatoes, corn, and low intakes of fruits, vegetables, whole grains, pasture-raised animal products, fish, nuts, and seeds.

Intermittent fasting is any of various meal timing schedules that cycle between voluntary fasting and non-fasting over a given period. Methods of intermittent fasting include alternate-day fasting, periodic fasting such as the 5:2 diet, and daily time-restricted eating (TRE).

<span class="mw-page-title-main">Diet and obesity</span> Effect of diet on obesity


Diet plays an important role in the genesis of obesity. Personal choices, food advertising, social customs and cultural influences, as well as food availability and pricing all play a role in determining what and how much an individual eats.

CALERIE is a trial currently underway in the U.S. to study the effects of prolonged calorie restriction on healthy human subjects.

<span class="mw-page-title-main">Weight management</span> Techniques for maintaining body weight

Weight management refers to behaviors, techniques, and physiological processes that contribute to a person's ability to attain and maintain a healthy weight. Most weight management techniques encompass long-term lifestyle strategies that promote healthy eating and daily physical activity. Moreover, weight management involves developing meaningful ways to track weight over time and to identify ideal body weights for different individuals.

Management of obesity can include lifestyle changes, medications, or surgery. Although many studies have sought effective interventions, there is currently no evidence-based, well-defined, and efficient intervention to prevent obesity.

<span class="mw-page-title-main">Added sugar</span> Caloric sweeteners added to food and beverages

Added sugars or free sugars are sugar carbohydrates added to food and beverages at some point before their consumption. These include added carbohydrates, and more broadly, sugars naturally present in honey, syrup, fruit juices and fruit juice concentrates. They can take multiple chemical forms, including sucrose, glucose (dextrose), and fructose.

<span class="mw-page-title-main">Sweetened beverage</span> Type of beverage

A sweetened beverage is any beverage with added sugar. It has been described as "liquid candy". Consumption of sweetened beverages has been linked to weight gain, obesity, and associated health risks. According to the CDC, consumption of sweetened beverages is also associated with unhealthy behaviors like smoking, not getting enough sleep and exercise, and eating fast food often and not enough fruits regularly.

The relationship between diet and longevity encompasses diverse research studies involving both humans and animals, requiring an analysis of complex mechanisms underlying the potential relationship between various dietary practices, health, and longevity.

References

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