Monkeys (more precisely chimpanzees) do not have fasting mechanisms. They never start fasting and go into ketosis, they just die from starvation after week or two. In tropics they have food available all year. They never venture far from food sources.
Humans (and other non-tropic animals like mice) have adaptation for seasonal food availability, and can go through extended fasting.
This should be higher up. Humans split from primates (including chimpanzees) roughly 5 million years ago. Early hominids only evolved the ability to store large amounts of fat and fast for extended periods of time in the Pleistocene, less than 2 million years ago. Any study done on calorie restriction using monkeys has a serious caveat. Mice offer a much better starting point for comparing metabolic activity.
You're kidding, right? I can see saying neither one tells you much about human beings, but saying monkey studies aren't relevant to human but mouse studies are just sounds bizarre.
If you're specifically studying something that is a stark difference between other monkeys and apes on one side and humans on the other, studying monkeys and apes is obviously not a smart thing to do.
> Five healthy rhesus monkeys, three male and two female, weighing from 2.4 to 6.1 kilos, were fasted for periods of 2 to 4 days... With one exception, the monkeys developed a ketosis within 2 days
Note that ketosis != fasting; ketosis == low carb, which can also be induced without fasting (but only by eating a low (near zero) carb diet). So are you sure you're not conflating 2 dimensions (how much we eat, vs what we eat)?
Funny enough, one of the reasons I respect Peter Attia, is that he's changed his mind several times, after new information came to light (i.e. he had an initial assumption based on weak evidence, then changed his opinion after he found stronger evidence). This is quite rare in general, an even rarer among the "influencers" (a.k.a. professional grifters).
The first time Peter Attia had to change his mind, is when his Nutrition Science Initiative (NuSI) collapsed. Long story short, his hypothesis was that carbs (or rather, the insulin response) make people obese, and that low carb diets drastically improve health. NuSi funded proper experiments to test this, i.e. they provided calorie-matched low-carb and non-low-carb diets. They failed to confirm the hypothesis.
Since you showed up on a Google alert (I co-founded NuSI with Peter) I'll respond.
NuSI funded two trials that could test the energy balance hypothesis. (This is an important point: these experiments tested the null hypothesis, which was energy balance, although the experimental tests were based on predictions made by the carb insulin model.) One trial, led by Kevin Hall and Eric Ravussin, was a non-randomized pilot study that they interpreted as consistent with the energy balance hypothesis. That interpretation was challenged by David Ludwig who led the other trial, an RCT that Ludwig interpreted as inconsistent with the energy balance, calorie-is-a-calorie model. Hall et al challenged that interpretation.
If Peter changed his mind, which his book suggests he did, it could not have been based on the results from the NuSI-funded trials because their interpretations were contradictory, as experiments in science often are. Peter cares deeply about scientific method so I'm sure he understands this.
I thought so too but this is newer research on monkeys based on a long running study since 1989 linked directly in the first sentence of the article: https://www.nature.com/articles/nature.2014.14963. That being said the Wisconsin study does have a fair amount of criticism in that they cut back on a diet composed 30% sugar from an all you can eat buffet so it’s unclear if it’s purely just stopping being overweight / reducing risk of diabetes or if there’s any other benefits.
FWIW as much as it’s fair to criticize the study design, an all you can eat buffet composed of 30% sugar is more or less par for the average American.
It’s not like we’re out here in the real world with a healthy and nutritionally balanced baseline. Most of us eat quite a bit of trash, so in the context of the real world the findings seem valid enough.
There’s a difference between “caloric intake reduces obesity related mortality causes like diabetes” and “caloric intake extends lifespan”. Even though they’re related, the latter is claiming everyone would benefit from it including those that aren’t obese and is fighting some kind of fundamental aging mechanism caused by eating while the former is just saying how to fix the American diet to fix obesity and diabetes.
What, if you don't eat the standard american diet? a lot of americans don't. I see a lot of carts in front of me at the grocery store with junk only in them, but there are also a lot with mostly healthy foods.
There have been recent studies on the impact of fasting during pregnancy. Here's two:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8377932/
> A total of 215 women were included in the study, 123 women fasted, and 92 women did not fast. Only 2.8% of women knew that fasting is forbidden in pregnancy. Sixty five percent of women reported weakness as the main reason for not fasting. The rate of gestational diabetes, pregnancy induced hypertension and preterm delivery was higher among women who fasted (17% vs 14%, 7% vs 2%, 9% vs 9%) respectively, compared to non-fasting women, but were not found statistically significant. There was no difference in anthropometric measurements of newborn, among both groups.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9931121/
> Fasting during pregnancy was associated with reduced birthweight, in particular for fasting during the first trimester (-352ˑ92g, 95% CI: -537ˑ38; -168ˑ46). Neither dietary composition nor altered sleep were directly associated with birthweight. However, dietary composition during Ramadan outside of fasting hours seems to moderate the fasting-birthweight association, which disappeared for women switching to high-fat diets.
The benefits can be negated by what you eat outside the fasting window. Anecdotally, a few guys I knew feasted on baclava and super sweet tea first chance they got. also not drinking any water during the fast, especially in hot climates might be net unhealthy independent of any fasting benefits. I don't know any studies on that though, happy to stand corrected...
Then religious muslims around the world, who all fast every year, must have the highest rate of medical issues related to their kidneys. Is there any such studies showing this?
Any studies done on potential health effects due to Ramadan will need to deal with the issue of noncompliance, i.e. to what degree do people observing Ramadan actually stick to the fast and not “cheat” at all. But I can imagine that due to the religious significance of the fast, you likely won’t get accurate self-reports of noncompliance. It would also be hard to conduct an accurate observational study since the subjects’ behavior will change due to being observed, again, because of the religious aspects. Without good noncompliance data, I’d be skeptical of any firm conclusions.
>>Haven't almost 1Bn people intermittently fasted during Ramadan for centuries?
As a Muslim, I can tell you we tend to over eat, generally after we break our fast. It kind of defeats the whole point of fasting. In most cases its unavoidable as breaking fast is a social event for most people.
Im guessing before food got abundant the results would be quite different, but again back then most of the world had little to eat any way.
The goals of fasting during Ramadan are not to train people for intermittent fasting. Its because the religion/god said so, and to some extent make you feel how the poor feel as thats how life works for them everyday.
There is also a thing about fasting every Monday and Thursday which pious people tend to do often. But in general I have seen only good things happen to people who eat less. Muslims or not.
> The investigators were comparing median survival between the CR and control (CON) groups, not longevity or lifespan per se.
As I read that, it wasn’t that the study showed that caloric restriction didn’t extent lifespan. It’s that they weren’t investigating the effect of caloric restriction on lifespan, so no conclusions can be made from the study.
TL;DR: there are 2 monkey studies, with unclear/conflicting results, both had pretty shitty diets, the calorie restrictions were severe, the benefits minimal at best.
The quote I provided was from the article. I’ve read the whole thing and I’m still parsing it (and your statement about both being fed shitty diets) as going against your original assertion: “Studies of caloric restriction in monkeys didn’t cause lifespan extension, casting doubt on its effect in humans.”
According to Attia, the studies weren’t specifically studying life extension, and all the diets were non-typical for the monkeys being studied. So, to me, this argues not that caloric restriction doesn’t cause lifespan extension in monkeys, but that we cannot know from these studies whether caloric restriction with a healthy diet causes lifespan extension in monkeys, which is what we really want to know. I wouldn’t expect to extend lifespan by eating hamburgers and fries but less of them, and that seems analogous to what the studies did.
To me, this simply leaves the question of caloric restriction in humans unanswered instead of casting doubt on it. Big difference.
Not anymore. More recent research has failed to find any real benefits to intermittent fasting, at least for people who are already at a healthy weight. And it seems to have some negative effects for body composition.
Note I used periodic instead of intermittent for a reason. I seem to recall he was recently for something like a day a day and a half fast per month. Don't follow him that closely, did he move away from that too?
It's generally uncomfortable to share meals with people who aren't eating. It's deeply ingrained in many cultures to "break bread" in a way, so I think that's why it can be perceived as rude.
and thrown out with the bathwater is we've bred these mice to be very similar to us in some cases. if you wanted these studies done on humans you'd be dead before the results came back positive or negative.
I know I’m just nitpicking here but I believe you mean “inconclusive”. If we knew the findings specifically to be incorrect then we’d be learning something.
I'm not advocating a bad scientific study. I'm advocating a good one for detecting what might be another cause of it not working for monkeys other than 'duh! monkeys aren't mice!"
It's not about finding something inconclusive or incorrect. It's about finding all the ways you can make caloric restriction not cause extended lifespan in mice without harming them in some obvious ways that are hard to apply accidentally in research setting.
For example, maybe caloric restriction doesn't work if you feed mice badly inappropriate diet.
The reason mice are used in labs isn’t because they’re a good model of humans, but because they’re easy to bread and have short lifespans.
Studies of caloric restriction in monkeys didn’t cause lifespan extension, casting doubt on its effect in humans.
Peter Attia (best source of longevity science) wrote about this 5 years ago.
https://peterattiamd.com/calorie-restriction-part-iia-monkey...