The effect of physical fitness on mortality is overestimated

53 gnabgib 67 5/18/2025, 10:42:50 PM uu.se ↗

Comments (67)

Noumenon72 · 4h ago
> Next, the researchers examined how fitness was associated with the risk of dying in random accidents such as car accidents, drownings and homicides. They chose random accidents because they assumed that there ought to be no association between the men’s fitness in late adolescence and the risk of dying in random accidents.

Blank slatism is the curse of the sciences. Of course the kind of people who die in car accidents and homicides are not identical to everyone else but for random luck. They're less educated[1], they make poor decisions, they have dangerous neighbors, frequently they're immigrants from countries with lots of car accidents and homicides. We've known that "everything is correlated" since 2014[2], when will science figure it out?

1. https://www.theverge.com/2015/10/2/9438197/traffic-accident-... 2. https://gwern.net/everything

JumpCrisscross · 4h ago
I’m also struggling to see how one’s risk of drowning isn’t obviously related to fitness. (The nexus between weight and car crash mortality isn’t exactly buried science, either [1].)

[1] https://pubmed.ncbi.nlm.nih.gov/11829292/

fawley · 3h ago
My university required a swim test to graduate, and also required 10 minutes of treading water in order to access sailboats. Many of my classmates talked about this being difficult, but both were trivial for me.

Fat is buoyant.

galangalalgol · 3h ago
Yeah you can have lots of spare energy and still be quite strong with great cardiovascular health. It is hard on the joints though.
JumpCrisscross · 3h ago
Some body fat is absolutely helpful in protecting from drowning [1]. You see a similar curve when mapping life expectancy and mortality risk against BMI—the optimum is a bit thicker than our guidance suggests. (Saying this as someone who has to fight to keep weight on.)

[1] https://pubmed.ncbi.nlm.nih.gov/28915131/

Teever · 3h ago
I could see a scenario where less fit people stay out of the water while people who are fit do more activities in the water and some of them engage in riskier activities in the water like whitewater kayaking.
JumpCrisscross · 3h ago
> could see a scenario where less fit people stay out of the water

Which further undermines the authors’ assumption that drownings are random accidents.

koolba · 3h ago
There’s an age dynamic as well. The most reckless people I knew at age 20 were the most physically fit. But that flipped in later years.
6510 · 3h ago
fit people swim, fat people float?
azan_ · 4h ago
Yes, and since there is a factor that affects both fitness and dying in car accidents or homicides, then it's harder to establish for how big reduction of mortality is fitness really responsible (causal). What you are complaining about is exactly the point of this study:

> This suggests that people with high and low fitness levels may differ in other important ways, which is something that previous studies have not fully taken into account

stepanhruda · 4h ago
I thought these studies often control for additional factors like wealth, education etc. not sure about this one, but genuinely curious whether I am mistaken and science “did not figure it out” yet
gwern · 4h ago
Those studies never 'control for those'. What they do is a crude statistical approximation (sometimes extremely crude - eg most studies will 'control for education' by counting up 'years', which equates 4 years at Caltech with 4 years in community college), and hope that not too much leaks through as "residual confounding" (https://journals.plos.org/plosone/article?id=10.1371/journal...). Unfortunately, because everything is correlated, there's residual confounding everywhere. This is why every time someone does a Scandinavian population registry study and compares eg siblings within the same family, often the correlation just disappears then and there.

It's 100% unsurprising that this is true of fitness too. This is what always happens. You look at something like a corporate health fitness plan and you find some correlate even after you 'control for' SES, prior health record etc etc; wonderful! Then you do a randomized experiment and it turns out that the residual confounding was still larger than any causal effect which might be there: https://gwern.net/doc/statistics/causality/2022-wallace.pdf Ah well. Maybe next time you'll manage to 'control for' the confounders...

ajross · 4h ago
You're misunderstanding. The point is absolutely not that the fitness/accident correlation must be fictitious. It's that the fact that it exists exists suggests that the fitness/cardiovascular-mortality link may not be as direct as previously understood.

It might be co-causal, for example: to take your list, maybe "making poor decisions" has a bigger impact on cardiovascular health than we thought.

Swizec · 3h ago
> It might be co-causal

Kinda like how wine after dinner improves health outcomes. The kind of people who can afford to regularly drink wine, but not a lot, also have more access to healhtcare.

Also riding horses makes you healthier! (it’s a proxy for wealth)

One could argue that high VO2max may just be another proxy for wealth. People who can afford to work out every day can also afford lots of other things that correlate with health and longevity.

conception · 4h ago
Any paper that starts with a blank slate and doesn’t control for confounding variables is unlikely to be published or accepted in.. like… high school.
andrewl · 4h ago
Like most people I want to live a long time. But more than life span I am interested in health span. I want to feel good and be autonomous as long as possible. Fitness, especially good muscle mass, is an important part of that.
Aurornis · 4h ago
The funny thing about the “healthspan” trend is that it’s simply describing what everyone meant when they said they wanted to live a long time.

Nobody wanted to live a long time but be unhealthy in their older years.

It wasn’t until health and fitness podcasters started holding up the “healthspan” term as something novel that we had to hear about the supposed difference.

It’s also unfortunate that the “healthspan” influencers frequently get into health trends that have the opposite effect. The main example I can think of is Dr. Peter Attia, who started out praising ketogenic diets (recently shown to have very negative effects on cardiovascular health, not surprisingly) and later Rapamycin (briefly praised by lifespan influencers until they all decided it was hurting more than helping).

I think one of the best things people can do for long-term health is limit their consumption of health and fitness influencers who are pressured to constantly invent and push new things to keep themselves relevant.

hollerith · 4h ago
Your comment ignores the main point of the comment you are replying to: namely, a lot of reporting on studies that find that some intervention increases lifespan ignore strong evidence that the same intervention fails to increase (or worse, actively decreases) healthspan. A diet low in protein for example, will tend to increase your lifespan while tending to make you one of those 70-year-olds (or 60-year-olds if you're unlikely or maintained a diet very low in protein) with very little muscle left -- and no way (that we know of) to regain muscle: at that age, neither exercise nor increasing dietary protein quantity and quality will significantly increase muscle mass even if muscle mass is very low.

I suspect that something similar can be said of not doing enough exercise.

We are commenting on a press release from a university, i.e., written by professionals whose job is to increase the prestige of their employer. It is rich for you to criticize Peter Attia, M.D., and ignore that little gem. At least Attia is trying to understand some aspect of reality more fundamental than impression management and increasing the public's awareness of whatever their employers tasks them to target.

Aurornis · 3h ago
> A diet low in protein for example, will tend to increase your lifespan while tending to make you one of those 70-year-olds (or 60-year-olds if you're unlikely or were very protein deficient) with very little muscle left

Low muscle mass is correlated with shortened lifespan, though. Very low muscle mass is known to be a high risk for early mortality.

> It is a rich for you to criticize Peter Attia, M.D., and ignore that little gem.

I don’t feel bad at all for criticizing Peter Attia, especially after his ringing endorsements of the Oura Ring and claimed “investor” status were revealed to be a contractual deal where he got shares in the company in exchange for promoting the Oura Ring. He’s been revealed to be very oriented toward fame and self-promotion, as evidenced by his recent claims that Kevin Spacey’s accusers were all wrong and Kevin Spacey was totally innocent after Kevin Spacey’s team set up a promotional dinner between Attia and Spacey. I know a lot of listeners develop sorts of parasocial defensive relationships for their podcasters, but you can’t deny the irony of a CVD-focused podcaster starting his podcast career deep into Ketogenic stuff before he saw the writing on the wall and backed off.

akoboldfrying · 3h ago
> and no way (that we know of) to regain muscle

https://www.theguardian.com/wellness/2025/mar/11/older-adult...

TL;DR: In the 1980s, Maria Fiatarone got 9 patients in their 80s and 90s to do 2 months of progressive resistance knee extension training. The minimum increase in 1RM strength was 61%.

hollerith · 3h ago
OK, but did the subjects add any glycogen storage capacity to their musculature? The muscles capacity to remove glucose from the bloodstream (and store it as glycogen) is very useful in avoiding uhealthy, high levels of glucose after a meal containing carbs.
iamthemonster · 4h ago
Which study are you referring to for keto having a negative impact on cardiovascular health? I've unfortunately found studies and metastudies reaching all sorts of conflicting conclusions on keto.

The top metastudies on a simple google search both conclude positive effects on CVD.

Aurornis · 3h ago
Ketogenic diet research is fascinating in itself for how many manipulated or misleading studies get published.

The most recent example is the KETO-CTA paper, which was released in April to loud claims that high LDL in a keto diet was not really bad. It got picked up by various news outlets as vindicating ketogenic diets. The authors posted long Twitter threads full of meme animated gifs celebrating their victory over keto skeptics.

Yet when people started looming into the study they noticed that the study failed to report the data from the pre-registered trial endpoint. This is highly unusual because if you establish an entire clinical trial, you are expected to publish the primary results you pre-registered.

After a lot of prodding, people finally got the authors to release the percent change in non-calcified plaque volume (NCPV) values that they pre-registered for and they were extremely high. Even higher than seen in certain serious medical conditions. It became clear that they chose to hide the values because they were so incredibly bad.

> The top metastudies on a simple google search both conclude positive effects on CVD.

There are a lot of die-hard keto defenders who produce papers, blogs, and podcasts claiming it’s either neutral or good for CVD. You have to look past the SEO optimized content and go to actual CVD experts who do not have their internet presence tied to promoting keto diets.

DennisP · 2h ago
I've read Attia's book, and all he said there about diet was that it was really hard to study, but the best study he knew of made the Mediterranean diet look pretty good.

He went into quite a bit of detail on exercise though, focusing on the predictable ways you'll lose capability as you age, if you don't work really hard on avoiding that.

blargey · 3h ago
I thought the whole trend of "healthspan" as a word was a direct response to / attempt to sidestep the many people who are convinced that any artificial increase to "lifespan" will doom humanity to either Tithonus or Altered Carbon and will fight you over it if you dare propose such a terrible, terrible thing.
strken · 3h ago
> Nobody wanted to live a long time but be unhealthy in their older years.

If nobody wanted that, then why have we spent so much effort keeping older people alive and in agony for a couple more days, often in direct opposition to their preferences and DNRs?

If nobody wanted a medical system that caused such suffering for such little reason, then how come the excellent How Doctors Die[0] needed to be written?

[0] https://www.saturdayeveningpost.com/2013/03/how-doctors-die/

blargey · 3h ago
An even stronger cultural and legal opposition to anything resembling suicide?
strken · 3h ago
That appears to me to be a revealed preference for lifespan over healthspan, except couched in different language.
gdudeman · 3h ago
I think that at best the jury is still out on Rapamaycin. It has healthspan- and lifespan-increasing effects on most animals studied.

Bryan Johnson quit using it, but he’s on 40 other things and there are bound to be drug interactions.

That said, limiting consumption of health and fitness influencers is bound to be good for lifespan: you’ll have more time to live.

And yes, it’s hard to make a living as an influencer saying “eat food, mostly green, move your body, and spend time with friends and loved ones.”

melling · 4h ago
Yes, everyone is interested in healthspan
generalenvelope · 4h ago
Dr. Feigenbaum from Barbell Medicine says "We want to add years to your life, and life to your years" :)
mlhpdx · 3h ago
> especially good muscle mass

I thought semi-starvation was the one and only strongly evidenced way too extend lifespan? Which obviously doesn’t require, and in fact destroys, muscle mass.

amrocha · 4h ago
I think personally I want to be bedridden, sick, and miserable for as long as possible but I respect your point of view too!
drewcoo · 4h ago
I'll just add that I don't want more of the last years of my life. I'd like more of the middle.
pmarreck · 4h ago
Exactly. And if you consider that every hour you spend purely exercising (gym, treadmill, etc.) in the middle does NOT pay for an extra hour of life on the tail end, it doesn’t seem like the best trade.

(I will say that a morning workout still supercharges your day!)

socalgal2 · 3h ago
> (I will say that a morning workout still supercharges your day!)

And you'd be wrong. It does not supercharge my day. Maybe it superchargers your day. Just finished my morning workout and now I feel like I've been drugged and need a nap. I do not feel "supercharged"

yakbarber · 3h ago
I don't think I'd agree with their hypothesis though that there's no connection between dying in a random accident and fitness.

Fit people:

1. more able to "get out of the way" / coordination / agility

2. faster reaction time

3. potentially suffer a reduced injury

4. more likely to recover than die from the injury

There's probably a dozen rational things we could think of to counter that hypothesis.

8note · 3h ago
5. more likely to be nearby certain types of random accidents

6. less likely to be nearby other types of random accidents

TylerE · 2h ago
You’re making assumptions not in evidence. It’s well documented for instance that drunk people do better in accidents than sober people precisely because their reactions are slower and they don’t tense up.
akamaka · 4h ago
They appear to have proven that by walking more and driving less, you have a lower chance of dying prematurely in an accident, but for some reason which they have yet to uncover, that effect is not due to the extra fitness you get from walking.
manwe150 · 3h ago
You also do have a higher chance when walking of getting fatally hit by a car (because right turn on red is legal in most of the US). So it probably isn’t quite that simple. I think that was one of the original Freakonomics book studies?
SchemaLoad · 2h ago
The study is from Sweden. Most of the world doesn't run people over nearly as much.
ahazred8ta · 3h ago
'accidents' includes non-vehicle related accidental deaths, such as "Hold my beer and watch me do this."
riskassessment · 4h ago
Probability of dying in a random accident is the probability of a random accident occuring times the probability of dying from a random accident conditional on one occurring. I am not convinced that fitness would be entirely unassociated with both of these probabilities, particularly the latter. Meaning that the extent to which this outcome is a good negative control is overestimated.
gregors · 4h ago
>>>> n the study, the researchers leveraged data from 1.1 million Swedish men

So in other words, light years better shape through out all age ranges compared to your average American.

gdudeman · 3h ago
This might explain how people who exercise for work do not seem to get the health benefits of people who exercise recreationally.

It’s not the exercise, it’s that people who recreationally work out are in a different socioeconomic group.

Also, this is consistent with many mouse studies.

SchemaLoad · 2h ago
A lot of the "exercise for work" stuff is quite dangerous
ohelabs · 4h ago
> In the study, the researchers leveraged data from 1.1 million Swedish men who were conscripted for military service between the years 1972 and 1995

For anyone from the US reading this just throw it out… we eat significantly less healthy and have significantly more obesity. Sweden as a country is significantly more healthy and active. To everyone reading this and thinking that this applies is sorely mistaken.

Fitness might not “extend your life many years” but being morbidly obese will most certainly end it significantly early.

strken · 3h ago
48.3% of the Swedish population are overweight or obese, per https://data.worldobesity.org/country/sweden-207/#data_trend....

This is obviously not military age swedes in the 90s. Still, it's not too far below the US's 70%-ish.

mensetmanusman · 2h ago
Who cares, a long healthspan feels great!
amluto · 4h ago
> Next, the researchers examined how fitness was associated with the risk of dying in random accidents such as car accidents

> The researchers found that men with the highest fitness levels had a 53 per cent lower risk of dying in random accidents. Yet, it is unlikely that the men’s fitness would have such a big effect on their risk of dying in random accidents.

Wait, what?

https://aaafoundation.org/rates-motor-vehicle-crashes-injuri...

The risk of being in a motor vehicle crash increases as one gets older than ~70 years. The risk of dying increases even more dramatically.

Now maybe this effect is independent of physical fitness, but that’s quite an assumption. I would guess the contrary: that poor fitness quite dramatically increases one’s risk of a car crash, both due to reduced motor control and increased risk of various neurological issues.

Vascular dementia, for example, seems very likely to be correlated and often caused by poor fitness. Various sources seem to think that exercise can quite dramatically reduce Alzheimer’s risk. Alzheimer’s disease is related to PCA, and I suspect that PCA is very much under-diagnosed and that it causes a lot of crashes.

azan_ · 4h ago
That's a very good point. However the median follow-up in the study was 56 with IQR 50 to 62 years, I think that reduces this issue a lot.
SchemaLoad · 3h ago
What do you mean by PCA? Didn't show anything relevant when I searched it.
amluto · 3h ago
Posterior cortical atrophy:

https://en.m.wikipedia.org/wiki/Posterior_cortical_atrophy

PCA can cause simultanagnosia and other problems with visual perception.

Have you ever seen an elderly person drive directly at you in a parking lot, at low speed, and appear to be completely unaware of your presence? This could be why.

anothernewdude · 4h ago
I'm a (fairly) fit runner. I run for about 8 hours each week, sometimes longer. I'm in a car so much less than the average person. Guess why.
cadamsdotcom · 2h ago
Can’t post a car ride on Strava.
amazingamazing · 3h ago
You live closer to work?
BrenBarn · 3h ago
Well, it stands to reason that more physically fit people would be better able to leap out of the way of an oncoming train, etc. :-)
knuckleheadsmif · 4h ago
There is mortality and there is quality of life and someone who is fit will have a better quality of life even if they don’t necessarily live longer.
amazingamazing · 3h ago
I’m skeptical that it’s worth it to spend too much time working out.

If there are three options:

1. Sedentary lifestyle (<3 passive or active exercise weekly).

2. Moderate (~1 hour passive exercise daily, like walking a dog a few miles daily).

3. Active (>1 hr active, like running several miles or lifting).

I think there’s huge value in moving out of (1), but am not sure if it’s worth going from (2) to (3) w.r.t longevity

User23 · 2h ago
All else being equal a more fit person is more likely to avoid an otherwise fatal accident.
TMWNN · 1h ago
>I believe that every human has a finite number of heartbeats. I don't intend to waste any of mine running around doing exercises.

—Attributed to Neil Armstrong

ninetyninenine · 4h ago
Finding a random association doesn’t establish causality or de-establish causality on another different association.

The causality was originally just assumed. Now with this new association, what changed? Logically nothing has changed right? There is no logical conclusion derivable from this.

deadbabe · 4h ago
I find that a lot of people these days seem to optimize their lifestyle for living up to about 50 years old, up to which point they don’t seem to care about dying off since life after that gets a lot more annoying and less enjoyable due to aging, and mounting debts that go unpaid and have no hope of being paid off. People can envision a good life up to about 50, but they struggle to imagine anything good happening after that since there aren’t many good examples on social media except for ageless rich people with all the time and money in the world.
_dain_ · 4h ago
>Next, the researchers examined how fitness was associated with the risk of dying in random accidents such as car accidents, drownings and homicides. They chose random accidents because they assumed that there ought to be no association between the men’s fitness in late adolescence and the risk of dying in random accidents. This method is called negative control outcome analysis and involves testing the validity of your results for a primary outcome by comparing them with an outcome where no association ought to be found. If, however, an association is found, it may indicate that the groups studied are not actually comparable, and that the study suffers from what is typically referred to as confounding. The researchers found that men with the highest fitness levels had a 53 per cent lower risk of dying in random accidents. Yet, it is unlikely that the men’s fitness would have such a big effect on their risk of dying in random accidents.

I haven't read the underlying paper so maybe they addressed this, but: couldn't this just be because sedentary/unfit people tend to drive everywhere? So they're involved in more car accidents than healthier people, who walk places more.

Also if you're fat and don't exercise, you've got a lower chance of surviving emergency surgery after a car crash, or swimming to safety after falling in water, or dodging a knife ... I don't think it's a given that physical fitness is unrelated to surviving those things.

imcoconut · 4h ago
I agree completely. Also definitions matter. Currently in the US one of the leading causes of death, if not the leasing cause, is opiods which the CDC classifies as “accidental overdose”. The healthiest people in the US are probably abusing opiods at lower rates and therefore less likely to die from the leading cause of “accidental death”. The study is from sweden but just pointing out that the assumption they make is flawed - “we should not expect a relationship between fitness and accidental death”.
azan_ · 4h ago
> I haven't read the underlying paper so maybe they addressed this, but: couldn't this just be because sedentary/unfit people tend to drive everywhere?

It could be and that's the point - the exact causal effect of fitness might be overstated because some mortality reduction might have stem from - for example - driving less.