Actually, the CR research is a lot more complicated than that. I hate to be the bearer of bad news, but a study like this is of very limited value, to put it diplomatically. The genetic variability is only one problem. A bigger problem is in the variability of the intervention itself in the studies. For example, the classic DR/CR simply means lower calories. But hidden in this, are studies that simply take the standard diet, and cut the amounts of food, this is sometimes called DR (dietary restriction), and studies that cut the calories, but re-balance various aspects of the diet, sometimes called undernutrition without malnutrition, and in human subjects, the distinction between CR and CRON (Caloric Restriction with Optimal Nutrition); in animal models of this, the researchers would cut the amount of food, but compensate the lost macro or micronutrients, sometimes both, so that even though the animal consumes less food like in DR, they get added vitamins and minerals to bring them back to 100% RDA, same for macros, by adjusting protein or fat or carbs proportions. So, imagine that you cut the food amount and end up with fewer calories, but also inadequate protein, so you adjust by giving fewer carbs, but more protein, you end up with same calories, but adequate protein. You can even adjust food volume, by providing greater or equal volume of food but less calorie dense, you eliminate or diminish the hunger. In human CRONies, some would consume huge amounts of calorie poor vegetables, like cabbage. One of the triggers of hunger is the signal of stretched stomach. A stomach that is stuffed signals satiety. You are stuffed with cabbage, not hungry, but low calories.
The point is, that the design of the studies matters a great deal. It is far beyond âcut caloriesâ. To give an extreme example, semi-starvation on a poor quality diet in Africa results in a very short lifespan. A well designed diet with the same level of semi-starvation calories results in a longer lifespan than ad libitum free eating normal diet.
There were two CR monkey studies, where one showed CR longevity benefit, and one did not. There were several differences between them (including sabotage by lab techs who âcompassionatelyâ secretly added food to the CRâd monkeys, lol!), but the diet composition was one of the key differences - one of them had good diet as would be found in their natural environment, fruits, tubers etc., and the others had terrible quality processed chow very high in sugar. Of what value would it be to average these two studies and draw conclusions about CR based on that. Yet this is what happens when you grab a bunch of studies without accounting for the dramatically different protocols. Not worth very much, sadly.
The quality of the diet matters a huge deal in CR. And it goes both ways. For example, if you took the Standard American Diet, and simply cut the amount - what is responsible for the effect? Eating fewer calories, or eating less toxic food like sugary drinks, processed meats, snacks and other processed foods? Less calories, or less toxins? What effect does it have if you feed an animal a processed chow from ingredients they would not encounter naturally or you feed them their natural diet? Do you think processed food is physiologically harmful only in humans? What do you think lab chow is?
The design of a study is of paramount impact. If I malnourish an animal with key nutrients in inadequate amounts, I can impair their immune system. Starving Africans have very poor immunity and die in droves from trivial infections. In CR studies with re-balanced diets, the CRâd animals have superior immunity compared to ad libitum controls, as the immune system is upregulated by hormetic stress. In other straight DR studies, the restricted animals with inadequate nutrition had poor immunity.
Again, once you get deep into an area, and read tons of studies, you can spot poor design of studies, including metastudies.
I would be very careful taking this study conclusions at face value.
