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§       Purpose of Calorie Restriction


§       How does Calorie Restriction Achieve its Purpose?


§       Claims about the Effectiveness of Calorie Restriction


§       Evidence in Support of Claims

§       Effects on Rodents

§       Effects on Primates

§       Effects on Humans


§       How Safe is Calorie Restriction?


§       How is Calorie Restriction Different from Anorexia?


§       Who is Presenting this Information?


§       Conclusions and the Future of Calorie Restriction


§       Bibliography



Purpose of Calorie Restriction


Calorie restriction slows the aging process and extends average and maximum lifespan in humans.  It accomplishes this by reducing the incidence of nearly all diseases associated with aging.


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How does Calorie Restriction achieve its Purpose?


Members of the Calorie Restriction Optimal Nutrition Society consume between 10-25% fewer calories than what is considered normal by the FDA and make sure to maintain proper nutrition by taking supplements and eating nutritious foods.  According to the FDA a moderately active male between the ages of 25 and 50 should consume approximately 3200 calories a day; the average male participating in a calorie restricted diet consumes 2000 calories or less a day.  The FDA recommended daily caloric intake for a moderately active female, between the ages of 25-50, is around 2300 calories; the average female partaking in caloric restriction consumes 1500 calories or less daily (



Researches have yet to find out why calorie restriction has anti-aging effects.  Here are some of the main theories of the possible biochemical mechanisms behind calorie restriction:


1.  Aging is caused by a build up of oxidative damage generated by reactive oxygen species (ROS) produced during cell respiration.  It has been shown that animals on a restricted calorie diet have less of this damage.  It is hypothesized that calorie restriction slows metabolism and thus slows the production of ROS, therefore creating less cell damage (Koubova & Guarente, 2003).


2.  Lack of protein turnover and thus an accumulation of damaged proteins may also be a cause of aging.  Calorie restriction may speed up the protein turnover rate and therefore slowdown the build up of damaged proteins.  This may occur because the body may start breaking down proteins when it runs out of fat to burn (Koubova et al., 2003).


3.  Aging is associated with increased rates of stress-induced apoptosis (cell suicide).  Calorie restriction works by inducing the expression of SIRT1, which promotes the long-term survival of irreplaceable cells.  SIRT1 is a key regulator of cell defenses and survival in response to stress.  When one is engaged in caloric restriction, SIRT1 is expressed in many of the body's tissues and cell survival is favored over cell death (Cohen, Miller, Bitterman, Wall, Hekking, Kessler, Howlitz, Gorospe, de Cabo & Sinclair, 2004). 


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Claims about the Effectiveness of Calorie Restriction


§       Extend average and maximum lifespan in humans.

§       Reduces the incidence of nearly all diseases associated with aging:

̃    Cancer

̃    Heart disease

̃    Diabetes

̃    Osteoporosis

̃    Auto-immune disorders

̃    Neurological decline

̃    Alzheimer's disease

̃    Parkinson's



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Evidence in Support of Claims


Studies of Calorie Restriction in Rodents


According to, a study led by Stephen R. Spindler at the University of California, Riverside found that when old mice were administered a calorie restricted diet; they immediately benefited health wise due to a slowing in the aging process. The mice ended up living six months longer than average.  Spindler also found that calorie restriction applied just after birth increased the mice's lifespan by four years, which is two times the average lifespan for mice.  Calorie restriction was also shown to slow development and the advancement of cancer in the mice 9 ( 



















Another study, conducted in 1995 at the Audie L. Murphy Memorial Veterans Hospital in San Antonio, Texas, found that rats on a calorie restricted diet lived longer due to altered levels of antioxidant enzymes, which reduced free radial damage associated with aging (Xia, Rao, Van Remmen, Heydari & Richardson, 1995).    


Studies of Calorie Restriction in Primates


The effects of calorie restriction in primates bring researchers another step closer to understanding the effects of calorie restriction in humans.  An article in Goddard's Journal states the studies conducted by the National Institute on Aging researcher George Roth show that monkeys put on a caloric restrictive diet experience a decrease in incidence of diabetes, fewer signs of spinal arthritis, and a prevention of the age-associated decline in melatonin levels (


How this all Relates to Humans


In 2004, a study was conducted to determine if the positive effects of calorie restriction on yeast could be replicated in rats and in human cells treated with a serum from the calorie restricted rats (Cohen et al., 2004).  The study found that calorie restriction in rats has the same beneficial effects as it does in yeast.  The expression of Sir2 deacetylase in yeast and the expression of SIRT1 in rats delays the aging process.  Cohen et al. (2004) also found that when human cells were treated with a serum from the calorie restricted rats, SIRT1 was activated in the human cells, which means that humans may experience the same anti-aging benefits seen in calorie restricted rats. 


There is also evidence of the benefits of calorie restriction in humans.  Researchers led by Dr. John Holloszy found that members of the Calorie Restriction Optimal Nutrition Society (CRONS) score significantly better on cholesterol, blood pressure, and insulin levels than people who consume a normal amount of calories (  In fact the average blood pressure in a person who eats a calorie restricted diet is 100/60, which is typical for a ten year old.  Another study on the effects of calorie restriction in humans found that people on a calorie restricted diet experienced reduced risks for heart disease and diabetes (


Outside of research, the people of Okinawa, Japan are living evidence of the benefits of following calorie restricted diet.  Okinawans eat 40% fewer calories than Americans and 17% fewer calories than the Japanese average, but they still maintain adequate nutrition.  Okinawa also happens to boast the longest average lifespan in the world and the highest percentage of centenarians.  Compared to American elders, Okinawan elders are: 75% more likely to retain cognitive ability, 80% less likely to develop breast and prostate cancer, 50% less likely to develop ovarian and colon cancers, 50% less likely to experience a hip fracture, and 80% less likely to suffer from a heart attack (   




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How Safe is Calorie Restriction?


Calorie restriction is not for everyone.  Without the proper precautions calorie restriction can be dangerous and detrimental to your health.


§       Many inhabitants of third world countries have a reduced caloric intake, but do not live longer due to inadequate nutrition. 

§       No one under 21 years of age should practice calorie restriction due to possible negative affects on brain development.

§       Women who are pregnant should not follow a calorie restrictive diet due to possible premature birth and low birth weight risks.

§       There have been some incidences of women who had low iron levels despite taking two times the recommended amount of iron. 

§       Bone health may decrease due to weight loss.  Bone mass needs to be monitored.

§       Extra sensitivity to cold may be experienced due to less body fat and decreased body temperature.


§       In a study where 20 healthy young males were put on a calorie restrictive diet for six months, the men experienced some negative side effects. They showed signs of depression, irritability, low energy levels, and loss of motivation ( 


A calorie restricted diet should:


§       Be executed gradually overtime.

§       Include only highly nutritious foods and supplements to avoid malnutrition.

§       Be supervised from the beginning by a knowledgeable physician.



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How is Calorie Restriction Different from Anorexia?





Calorie Restriction



Motivation is a long healthy life


Motivation is to be in control by starving oneself



Seek support from physicians to ensure meeting nutritional needs



Hide condition from physicians and others


Come in all shapes and sizes



Drastically underweight


Concerned with achieving optimal nutrition with as few calories as possible


Concerned with consuming as few calories as possible or not eating; have no concern for nutrition



Mind not preoccupied with food



Mind preoccupied by disorder





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Who is Presenting this Information?


§       Jana Koubova and Leonard Guarente wrote on the mechanisms of calorie restriction.  Koubava has a Ph.D. in biology from MIT.  Guarente has a Ph.D. from Harvard and is currently doing research on the molecular mechanisms that regulate aging.


§       Haim Y. Cohen, who wrote on the role of SIRT1 in calorie restriction, has a Ph.D. and is a senior research fellow at Harvard Medical School.


§       Stephen R. Spindler, who did research on the effects of calorie restriction on mice, has a Ph.D. and is a professor of biochemistry at the University of California, Riverside.


§       Dr. John Holloszy, who assessed the health of members of CRONS, is a professor of internal medicine, chief of the division of geriatrics and gerontology and director of the applied physiology section at the Washington University School of Medicine.  His main area of research is the impact of exercise on health.


§       Ian William Goddard, who wrote on whether calorie restriction can extend the human lifespan, has his own website ( where he writes articles on health issues.


§       The Calorie Restriction Optimal Nutrition Society is a group of people, including medical doctors, who practice calorie restriction.  They have a website that gives information on calorie restriction (


§       George S. Roth conducts research on calorie restriction at the National Institute on Aging where he is a senior guest scientist.


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Conclusions and the Future of Calorie Restriction


According to an article written in Scientific American, we may not have to worry about eating a calorie restricted diet in the future to reap the anti-aging benefits.  Scientists are working on developing a pill that would mimic the effects of a calorie restricted diet in people who ate a normal amount of food.  The drug that has been studied the most is 2DG (2-deoxy-D-glucose).  It works by interfering with the cells' processing of glucose.  2DG is similar in shape and size to glucose; therefore it interferes with the process by binding to the enzymes that digest glucose, which then slows down glucose metabolism and ATP production, which is thought to be associated with aging.  The problem with 2DG is that it has been found to be toxic in certain doses in animals, therefore it is not yet safe to administer to humans (Lane, Ingram & Roth, 2004).


Calorie restriction is not for everyone.  If the regime is not followed with extreme care one risks the chance of becoming malnourished and therefore not gaining any of the benefits associated with calorie restriction.  Many people also my find such a meager diet difficult to remain on.  There are still benefits to eating a healthy low calorie diet without drastically decreasing calorie consumption.  So until there is a magic pill for youth…eat healthily, exercise regularly, sleep well, and you will live a long healthy life.


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Boyles, Salynn.  (2004, April 19).  Calorie Restriction Lowers Heart Risk: Study is First in Humans to Show Protection Against Disease of Aging.  WebMD Medical News.  Retrieved September 8, 2004 from World Wide Web:


Cohen, Haim Y., Miller, Christine, Bitterman, Kevin J., Wall, Nathan R., Hekking, Brian, Kessler, Benedikt, Howitz, Konrad T., Gorospe, Myriam, de Cabo, Rafael, & Sinclair, David A.  (2004, July 16).  Calorie Restriction Promotes Mammalian Cell Survival by Inducing the SIRT1 Deacetylase.  Science, 305, 390-392.


Edelson, Ed.  (2004, April 19).  Cutting Calories Can Prolong Life: Small Study of Disciplined Dieters Finds Many Benefits.  HealthDay Reporter.  Retrieved September 8, 2004 from World Wide Web: http://www.healthday/com/view.cfm?id=518451


Goddard, Ian Williams.  (2002).  Eat Less Live More.  Goddard's Journal.  Retrieved September 13, 2004 from World Wide Web:


Koubova, Jana, & Guarente, Leonard.  (2003).  How Does Calorie Restriction Work?  Genes & Development, 17, 313-321.


Lane, Mark A., Ingram, Donald K., Roth, George S.  (2004).  The Serious Search for an Antiaging Pill.  Scientific American, 14, (3), 36-41.


Restricting Calories may Increase Lifespan: Sensible Eating Slows Aging Process, Researchers Say.  (2004, March 22).  The Associated Press.  Retrieved September 8, 2004 from World Wide Web:


Xia, E., Rao, G., Van Remmen, H., Heydari, AR., Richardson, A.  (1995, February).  Activities of Antioxidant Enzymes in Various Tissues of Male Fischer 344 Rats are Altered by Food Restriction.  Journal of Nutrition, 125, (2), 195-201.



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