3 replies to this topic

[Leon93]

https://www.research...on_participants

BMI and all cause mortality: A huge systematic review and non-linear dose-response meta-analysis involving 230 cohort studies from 2016 which followed over 30 million participants for over 20 years found the best longevity outcomes (lowest all-cause mortality) for BMIs of around 21 for both males and females (figure 3, right bottom one)!
They controlled for factors like smoking off course.

Does this mean lower BMIs are better for longevity and all-cause mortality than higher BMIs? And as we can see from both figure 3 and 4 is that the longer the follow-up, the lower BMI has better results.

Some of you would probably say that BMI doesn't account for body composition. But the main thing is that even at BMIs of 21-23, most people in general still arent very fat and actually carry proper muscle tissue around. If body composition was that important, wouldnt we see a different outcome?

The study also notes:
_For the primary analysis we used the model from each study that had the greatest degree of control for potential confounding, with the exception of studies that also adjusted mutually between BMI and waist circumference and waist to hip ratio or that adjusted for potentially intermediate variables such as diabetes, hypertension, and serum cholesterol, for which we used the multivariate model without such adjustment if available._

I also remember another longitudinal study involving 1,46 million caucasians which found that BMIs of 20 actually had the best all-cause mortality longevity outcomes (http://www.ncbi.nlm....les/PMC3066051/). However, that study actually had a 15 year follow-up, rather than a 20 year follow-up.

https://www.ncbi.nlm...les/PMC4032609/
This study also saw lowest diabetes risk at BMIs 21 (figure 2) and lower (but perhaps higher when going anywhere between 18.5 and 20).

Even moreso, the link between high (but also low) IGF-1 levels (commonly asscociated with muscle mass, strength/resistance training and the like) and lower longevity outcomes is also pretty well documented.

And last but not least, another study (https://www.amjmed.c...0138-7/fulltext) in elderly concluded that elderly with about 5+ kg of muscle mass in males had better longevity outcomes than those who did not. 5 kilograms is not a lot at all. Difference between 25th and 75th percentile was 1.6kg/m2 (9.2kg/m2 versus 10.8kg/m2), which equals exactly to 5 kg in a 6 feet or 180cm average male. However to be fair, perhaps higher muscle mass could be having even better outcomes. And muscle mass indexes around 10.0kg/m2 in males, I dont know what that would look like. Maybe that is not having a lot of muscle or actually the opposite.

So what do you guys think of this? Noteworthy is also how many of the gurus at Longecity.org seem to promote lower BMIs rather than higher ones (I've seen everything from 17 up to 22 or so).

Attached Files

•  non-linear-doseresponse-analysis-of-bMi-and-all-cause-mortality-in-never-smokers.png   111.67KB   0 downloads
•  2iatm61.jpg   72.35KB   0 downloads

Edited by Leon93, 21 February 2019 - 05:20 PM.

[Oakman]

Interesting, but it looks to me that the sweet spot(s) with roughly equivalent risk are between 20-24, not less than 21 as your headline states. From the study...

 

"...increased risk of all cause mortality and the nadir of the curve was observed at BMI 23-24 among never smokers, 22-23 among healthy never smokers, and 20-22 with longer durations of follow-up. "

[Leon93]

@Oakman

Thank you for your reply. Yes, this study found that healthy never-smokers with longest follow-up had best longevity outcomes at 20-22 (figure 3, right-bottom one). The reason why I still said <21 is because the longer the follow-up, the lower BMI seems preferable. It is therefore only reasonable to <21, but I admit that is mere hypothesis.

Another reason I said <21 is the other two studies finding slightly lower preferable ideal outcomes at 20 or perhaps lower.

I also just attached the file of the third study:
 acel0013-0391-f2.jpg   69.39KB   0 downloads

Edited by Leon93, 21 February 2019 - 06:13 PM.

[Leon93]

Personally, I think all of this would suggest BMIs of between 19-21 or 20-21 would be best long-term. Going below 19 also often seems to have deleterious effects. Having some muscle mass still seems to have beneficial outcomes. So aiming for about 8-12% body fat, up to 15% perhaps for males seems best to me at least. That would still leave room to build sufficient muscle for BMIs of about 20 or 21.

But to be fair, perhaps a longitudinal study with multiple groups of people of all kinds of body compostions with different BMIs and same diet (bodybuilders with low BF% and high muscle mass versus those with low BF% and lower muscle mass like swimmers, (half-)marathon-))runners, cyclists etc. would be best to test this. I do notice most gurus here on Longecity advocate a vegetarian or WFPB (vegan) diet, so that diet choice would be best perhaps.

CR advocators would disagree with me I think, but afaik I thought CR was only truly effective in rats... but I admit I don't know the science of CR'ing in humans very well...

Edited by Leon93, 22 February 2019 - 08:02 AM.