Impact of caloric and dietary restriction regimens on markers of health and longevity in humans and animals: A summary of available findings

Impact of caloric and dietary restriction regimens on markers of health and

longevity in humans and animals: A summary of available findings

Nutrition Journal 2011, 10:107 doi:10.1186/1475-2891-10-107

John F Trepanowski (jtrepa2@uic.edu)

Robert E Canale (rcanale@memphis.edu)

Kate E Marshall (kmarsh14@uthsc.edu)

Mohammad M Kabir (mkabir@memphis.edu)

Richard J Bloomer (rbloomer@memphis.edu)

ISSN 1475-2891

Article type Review

Submission date 23 June 2011

Acceptance date 7 October 2011

Publication date 7 October 2011

Article URL http://www.nutritionj.com/content/10/1/107

OVERALL SUMMARY AND CONCLUSIONS

CR has been demonstrated to extend the maximal lifespan of a diverse group of species. 24

This extension of life is maximized when: 1) the magnitude of CR is elevated to the highest

possible value before inducing malnutrition and 2) the duration of CR is maximized. Animals on

CR regimens exhibit a variety of improvements in overall health in general and cardiovascular

health in particular. Unfortunately, the likelihood of discovering whether or not CR extends

human life is rather remote due to the ethical and logistical limitations of research design. The

optimal magnitude and duration of CR for humans will also likely never be known for the same

reason. Nonetheless, many human CR studies have noted favorable changes in biomarkers

related to cardiovascular and glucoregulatory function, which likely relate to quality of life and

may relate to longevity.

Due to the austerity of following a CR regimen of sufficient magnitude and duration,

alternatives such as CE, ADF, and DR may prove to be more appealing. The most pertinent

consideration to make when evaluating these alternatives is whether or not they elicit benefits

that are comparable to CR. ADF has been demonstrated to extend life and improve both

cardiovascular and glucoregulatory funnction in animals. Human trials have noted heterogeneous

findings and sex-specific differences regarding ADF’s effects on glucoregulatory function.

Unfortunately, it is difficult to compare the effects of ADF and CR regimens across different

studies due to an enormous number of confounding variables. Future studies should feature an

ADF group and a CR group so that direct comparisons can be made. Regarding DR, neither

carbohydrate restriction nor lipid restriction extend life. However, protein restriction appears to

extend maximum lifespan by 20%. Recent findings suggest that methionine restriction may be

the single cause of life extension observed in protein restriction studies. Future studies should

examine the effects of different magnitudes of methionine restriction on life extension.

As noted above, considerable research has recently focused on whether CE augments any 25

of the health-promoting benefits caused by CR alone. Very few conclusions can currently be

made due to the mixed results of the studies. CE does not appear to extend life beyond any

extension observed to be caused by CR. However, CE may be more manageable for many

individuals due to the smaller reduction in dietary calorie consumption. Future work in this area

should examine different exercise intensities, volumes, frequencies, and modalities.

Also, future work should compare different amounts of exercise-induced caloric expenditure.

Islamic Ramadan, the three principal fasting periods of Greek Orthodox Christianity, and

the Daniel Fast each provide a unique and interesting vantage point for evaluating the effects of

food restriction/modification. The majority of findings related to Ramadan fasting are mixed,

and these discrepancies are most likely due to the differences in cultural norms – particularly

dietary norms – of the groups studied. The three Greek Orthodox Christian fasts appear to

decrease body mass and lower both total and LDL cholesterol levels, although these fasts

minimally affect the intake of most vitamins and minerals. Finally, the Daniel Fast is associated

with profound and favorable effects on a variety of markers related to human health, including

blood pressure, blood lipids, insulin sensitivity, and biomarkers of oxidative stress.

This paper has touched on some of the numerous methods of restricting dietary intake.

Whether one chooses to restrict energy intake daily, fast every other day, restrict intake of a

particular macronutrient, or fast for religious purposes, the authors hope that this paper can serve as a valuable tool to understanding the ability of dietary modification to improve overall health and the quality of life. Furthermore, we hope that this information will fuel the development of new ideas and research studies focused on investigating the health benefits of caloric and dietary

restriction.

Abbreviations: ADF, alternate-day fasting; ASUI, Asthma Symptom Utility Index; BDNF,

brain-derived neurotrophic factor; CALERIE, Comprehensive Assessment of Long Term Effects

of Reducing Caloric Intake; CE, caloric restriction combined with exercise; CR, caloric

restriction; DR, dietary restriction; FEV1, forced expiratory volume; HDL, high density

lipoprotein; LDL, low density lipoprotein; MDA, malondialdehyde; MI, myocardial infarction;

mini-AQLQ, mini-Asthma Quality of Life Questionnaire; PEF, Peak Expiratory Flow