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Safety of two-year caloric restriction in non-obese healthy individuals


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Safety of two-year caloric restriction in non-obese healthy individuals.

Romashkan SV, Das SK, Villareal DT, Ravussin E, Redman LM, Rochon J, Bhapkar M, Kraus WE; CALERIE Study Group.

Oncotarget. 2016 Mar 15. doi: 10.18632/oncotarget.8093. [Epub ahead of print]

PMID: 26992237 Free Article







The extent to which sustained caloric restriction (CR) in healthy non-obese adults is safe has not been previously investigated.




Assess the safety and tolerability of sustained two-year CR intervention in healthy, non-obese adults.




A multi-center, randomized controlled trial. Participants were randomized using a 2:1 allocation in favor of 25% CR vs. Ad-Libitum intake (AL). Adverse and serious adverse events (AE, SAE), safety laboratory tests, and other safety parameters were closely monitored.




Three participants were withdrawn from the CR intervention because of the safety concerns. No deaths and one SAE was reported by participants in the CR group. Although the difference in AE between AL and CR groups was not significant, within the CR group, the incidence of nervous system (p = 0.02), musculoskeletal (p = 0.02) and reproductive system (p = 0.002) disorders was significantly higher in the normal-weight than in the overweight participants. At months 12 and 24, bone mineral densities at the lumbar spine, total hip, and femoral neck of participants in the CR group were significantly lower than in those in the AL group.




Two-years of CR at levels achieved in CALERIE was safe and well tolerated. Close monitoring for excessive bone loss and anemia is important.




Gerotarget; calorie restriction; dietary energy restriction; humans; safety

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Al Pater wrote:



Al, 'wow' is not a very helpful assessment of this study. Care to share why you think this new CALERIE publication (PMID 26992237) is noteworthy? 


Nothing looked too astonishing to me about it. A drop is bone density in the CR group, and potential problems with anemia & loss of menstruation aren't very surprising. If anything, what was surprising to me was how many more minor (and sometimes, relatively major) complaints the CR group had relative to the AL group. I generally think people start to feel better when the lose weight, but in this case, the CR group had a lot more complaints and minor maladies. Here are a couple tables from the paper illustrating what I mean:




Note from the left column in the above table, none of the increases in maladies in the CR group were statistically significant. But still, they are going in the opposite direction to what I'd expect.


Below are blood test anomalies compared between the AL and CR groups. You can see many of the same changes in the CR group that those of us practicing CR "in the wild" exhibit, including a higher likelihood to have low WBC counts, lower iron/hemoglobin status, elevated MCV & MCH.




Again none of the rise to the level of being significantly different, and at least some of these differences I consider to be positive signs, rather than causes for concern.  But overall, I would say that CR doesn't come across as very helpful by these measures of side effects or changes in blood markers, at least as would be interpreted by the general public and conventional medical wisdom. 



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  • 3 weeks later...



Hey Dean, maybe they are just grumpier and complaining more cause they are in a bitchy mood!


Not a bad hypothesis Mike. But as was pointed out here, the CR subjects in the CALERIE study reported better mood and less depression than controls (PMID: 26187233). Here is the data from the supplemental material of PMID 26187233:




The depression scores for the AL and CR groups started out identical. After two years, the AL folks' depression score went up (got worse) while the CR folks remained about the same, and so was significantly better than the AL folks by the end of two years. Even at the mid-point of the study (when you might expect complaints to be higher), the CR folks reported being in no worse mood than controls.


I guess you could still argue they might not have low mood, but just be bitchy!



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