Memory, cognition, and mood
While some scientists, particularly those working with ketogenic diets, have suggested that reduced calorie intake is associated with better cognition, two examinations into the data from the CALERIE cohort found differing observations.
The first was looking for associations between interleukin 6 (IL-6), a major inflammatory marker, with working memory. While the authors did find that a reduction in IL-6 led to improvements in spatial working memory tests, it was also clear caloric restriction (CR) was not what was driving the improvements.
Indeed, another study used a Cambridge working memory test, rather than IL-6 to measure performance of memory over the entire 24-month CR period, and found that spatial working memory improved, but that it could be down to a variety of factors, not necessarily energy intake.
In short, your memory could very well improve under conditions of CR, but it’s not exclusively the fact that you’re eating less that’s improving it.
Cognition, described as verbal memory, visual memory, and attention/concentration, was not improved at all.
Other neurological areas were improved, such as behavior, mood, and sleep, and even spontaneous physical activity, which was unchanged even under the conditions of a 24-month period of caloric restriction.
Evaluated at 12 and 24 months for neuropsychology, the participants took the most widely-used self-reported depression test and recorded lower scores of depressive symptoms and tension. Self-reported scores for mood, general health, and sexual drive all improved simultaneously, with another measure, termed “vigor” going up as a result.
Sleep hours and quality as measured by the Pittsburg Sleep Quality Index, went up as well. It was determined then that quality of life increased as a result of caloric restriction.
Biological aging
In the first part of this report, WaL examined things that have an effect on biological aging such as inflammation and cardiovascular health, but the trialists’ data also produced some studies that looked at biological markers of aging as such.
Breath may have been held for some people, as these results were being determined, as the consensus that if one eats less they will live longer was pretty well-established through evidence of it in many lower-order animals such as nematodes, mice, yeast, and more.
There are several measures of biological aging beyond someone’s chronological age, such as telomere length, and epigenetic clocks that measure DNA methylation. One study described them as “biological…proxies for extension of healthy life span in trials of geroprotective therapies that aim to slow aging”.
With such a delicate yet important measurement, an accurate marker is essential. Fortunately, one study used the CALERIE trials to examine two of these different aging measurements and found both reduced biological age in the CR participants.
Another trial looked at DNA damage, a key indicator of biological aging, was reduced across the board even when the CR cohort was split into 5 different groups which included some who exercised regularly or ate less than others. That same trial found fasting glucose levels fell under periods of long-term CR irrespective of the various cohorts, while core body temperature was reduced in the CR and CR + exercise groups. A lower core body temp and a low fasting glucose level are both markers of longevity.
For years scientists had to extrapolate theories on CR and longevity based on animal models, but the Duke University CALERIE trials have essentially proven that CR as a topic in the study of human aging is not only real, but a gold mine of potential disease mitigation research. WaL
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