What is calorie restriction (CR)?
Calorie restriction is generally associated with eating ~30% less calories, a very vague definition. According to the calorie restriction society, calorie restriction is defined as reducing caloric intake while still consuming an adequate amount of vitamins, minerals and other essential nutrients. It's suggested that you eat calorie-sparse, nutrient-dense foods; avoiding simple sugars and flours, eating leaf and non-leaf vegetables, maintaining an intake of .6-.8g of protein per kg of body weight, avoiding saturated fats, and consuming omega-3 fatty acids. It is only after you have improved the quality of your diet that should you begin reducing calorie intake. The desire is to lose weight slowly, rather than a drastic cut. Therefore, it is recommended to spend anywhere from 6-9 months to 1-2 years reducing your calorie intake. It is also very important to consult a physician prior to enacting any significant changes to your diet.
How does calorie restriction work?
The goal of calorie restriction is to slow down the aging process and all of the age-related diseases associated, such as cardiovascular disease, diabetes, and neurodegenerative diseases. It is suggested that calorie restriction may have a neuroprotective role and the proposed mechanisms by which this occurs are as follows: regulation of sirtuins, regulation of autophagy, increase in stress resistance, enhanced antioxidant effects, increase in neurotrophins, and regulation of Peroxisome proliferator-activated receptors (PPAR). The two areas I would like to focus on are regulation of sirtuins and increases in stress resistance. Sirtuins are a family of protein deacetylases, known as SIRT1-7 in mammals. SIRT 1 has been associated with neuroprotection in animal models, possibly effecting a number of proteins that are involved in preventing apoptosis and oxidative stress while increasing DNA repair and stress resistance. However, research is still limited and additional research is needed on the entire family of sirtuins to discern out the specific location and role of each member. Although stress resistance has been linked with sirtuin regulation, other possible mechanisms include better control over reactive oxygen species (ROS) and repair of oxidative damage, along with up-regulation of chaperone proteins, which prevent misfolding of proteins and subsequent destruction of misfolded proteins.
Calorie restriction in humans
So far there has been no definitive research on humans as to whether or not CR acts to increase quality and duration of life. However, CR has shown to be beneficial in a wide range of organisms, from yeast to primates, such as rhesus monkeys. There have been doubts as to whether or not CR will provide the same benefits for humans as it has for other species. Even if CR can reproduce some or all of the benefits, it is highly unlikely that CR will become a wide spread practice due to the obvious difficulties of following such a regimen. Therefore, the knowledge gained from CR studies is being used to attempt to develop therapies which utilize such mechanisms for treating age-related diseases, including drugs that target sirtuins, induce chaperones, and boost neurotrophins.
Although calorie restriction might not be the elixir for ever-lasting life, it may provide insight into cellular mechanisms that can benefit a whole range of age-related diseases, including neurodegenerative diseases such as Alzheimer's and Parkinson's.
Resources
http://www.calorierestriction.org/
Duan W, Ross CA. Potential Therapeutic Targets for Neurodegenerative Diseases: Lessons
Learned from Calorie Restriction. Current Drug Targets 2010; 11: 1281-1292
Like you said, I think calorie restriction is a very tough thing to implement. While it probably does help the aging process and would decrease the likelihood of some horrible diseases, I think there is more risk in what humans would cut out. It is much easier to give a mouse or a monkey decreased calories because they are so controlled in a lab, but with humans I would be afraid that people would be cutting out the wrong things and thus being even more unhealthy.
ReplyDeleteAn interesting variation on this is alternate-day calorie restriction. On one day you eat 30-50% of you target calories, and the next day you eat ad libitum. It seems to still have the same overall health effects, and the calories average out to about the same.
ReplyDeleteSBrookshire495K
This is very interesting. I think the average american could benefit from this, because most americans tend to over eat the recommended amount of calories per day anyway, although it would also depend on the amount of physical activity per day of that individual. I agree with katelyn that humans might cut out the wrong things, which can be even more unhealthy. On the other hand maybe the reduction of unhealthy food from there total unhealthy diet might still be beneficial, and may prolong the onset of diabetes which is super high right now.
ReplyDeleteHow very intriguing..but here is the skeptical side: Perhaps as we think about this, we should focus on the obesity epidemic sweeping across America. We are the fattest country in the world, with our healthcare system dominated by obesity related co-morbidities. Most Americans are unable to cut calories to a reasonable amount ( like 2000 kcal's per day) even under the duress of a serious medical condition. I cannot imagine that most would therefore cut calories simply to "live longer". Those who would be likely to follow such a rigorous regimen are also likely to eat healthy, high fiber, low fat diets, and exercise regularly. So, is it really caloric restriction that is beneficial, or simply better overall lifestyle?
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