One point frequently stressed in recent times when evaluating CR studies, is the possible role of feeding time in CR’d animals. Traditionally, this aspect was ignored for decades. An ad-lib (control) mouse/rat was of course given access to food, and the animal would eat whenever it wanted to. Whereas for the CR’d animal, the practice was usually, to cut back on the amount of food, and simply dump that amount into the cage. Well, in reevaluating those studies decades later, researchers observed that there was an unaccounted factor of meal timing - the controls had access to food at all times, so would eat regularly throughout the day (night). Meanwhile, the CR’d animals were very hungry, so they’d immediately consume all food in one go. And then, remain without food for the rest of the time (23+ hours), until the next portion of food was delivered the following day. Now today’s researchers in going back to all those old CR studies, started wondering to what degree the CR effect was due to just the calorie restriction, and to what degree to the, in effect, TRF (Time Restricted Feeding), or intermittent fasting - keeping in mind that a 23 hour fast in a mouse is physiologically significantly longer than 23 hours in a human.
What could be said, is that in most of those studies, the mice were subject to both CR, and TRF (or IF).
Here is what I personally find interesting. These mice/rats were on pretty robust IF. Yet, one of the famous and pretty universally observed effects of CR, is the coat/pelt quality difference between the CR’d (and IF’d!) animals and the ad-lib controls. The CR-IF animals always had much better, younger, healthier, less gray, thicker coats.
How does that multi-decade-observed in thousands upon thousands of animals effect square with this “bad for hair” result in this one tiny study in mice?
The following study is a goldmine of priceless data on CR, TRF/IF in rodents, with a veritable who’s who of researchers. If you ever wish to speak of these subjects, you cannot do without reading this paper:
Quote:
"Abstract
Calorie restriction (CR) promotes healthy aging in diverse species. Recently, it has been shown that fasting for a portion of each day has metabolic benefits and promotes lifespan. These findings complicate the interpretation of rodent CR studies, in which animals typically eat only once per day and rapidly consume their food, which collaterally imposes fasting. Here, we show that a prolonged fast is necessary for key metabolic, molecular and geroprotective effects of a CR diet. Using a series of feeding regimens, we dissect the effects of calories and fasting, and proceed to demonstrate that fasting alone recapitulates many of the physiological and molecular effects of CR. Our results shed new light on how both when and how much we eat regulate metabolic health and longevity, and demonstrate that daily prolonged fasting, and not solely reduced calorie intake, is likely responsible for the metabolic and geroprotective benefits of a CR diet."
Quote:
“The quality of the coat condition and fur color were diminished in both AL and Diluted AL mice, while CR mice retained a healthy coat (Figs. 6F–G).”
I think, quite frankly, that the overwhelming evidence from decades of reseach points away from this one peculiar result. YMMV.
