CALERIE is an ongoing series of studies on calorie restriction in humans and its effects on measures of health and metabolism. In this blog post you'll find some notes on results from the latest phase, yet to be published formally, but presented at conferences:
Three speakers described how a select group of 220 healthy volunteers [chose] to shun a quarter of their dietary calories in the hope of improving their long-term health and, potentially, extending lifespan. These participants of the CALERIE phase 2 trial were randomized to 25 percent CR or ad libitum eating. The large NIH-funded, mulitcenter, parallel group, randomized controlled trial was designed to evaluate how a calorie restricted diet affected biomarkers of aging and age-related disease over the long-term.
The primary aim of the trial [was] to evaluate whether 25 percent CR resulted in a sustained metabolic adaptation. One of the underlying theories of how CR worked is that attenuates the biological aging process by reducing resting metabolic rate (RMR) leading to reduced cumulative oxidative damage from aerobic respiration. [However] the calorie restriction did not cause a change in body temperature that would be indicative of reduced resting metabolic rate that would show adaptation. These data (which are not published yet) are currently being evaluated for proper interpretation. [The] findings are interesting because they are inconsistent with previous studies in animals and a recently in humans showing a metabolic adaptation through RMR and core body temperature in response to CR.
"Basically, these are the primary mechanisms in humans - reduction of metabolic rate and core body temperature - we did not find an adaptation in the resting component, but we did find an adaptation in the non-resting component. If there was a reduction, that is supposed to lend support to the oxidative theory. What exactly this means is still being worked out."
The long-term CR had a significant effect on a variety of [cardiovascular disease risk factor] measurements including a reduced metabolic syndrome score, reduced systolic blood pressure, reduced LDL, reduced triglycerides, and increased HDL that were maintained over the study. There were no significant differences on glucose measures or inflammatory markers IL-6 and TNF-a. These results are consistent with previous studies related to reductions in body weight.