Monday, July 12, 2021


We have had some confusion over the years, including recently, what it means for something to be "genetic."  While reading a Scott Suskind at Slate Star Codex article from 2017 about weight loss I came across a quote that captures a lot of what I think is missing. 

Right now, within this culture, variation in BMI is mostly genetic. This isn’t to say that non-genetic factors aren’t involved – the difference between 1800s America and 2017 America is non-genetic, and so is the difference between the perfectly-healthy Kitavans on Kitava and the one Kitavan guy who moved to New Guinea. But once everyone alike is exposed to the 2017-American food environment, differences between the people in that environment seem to be really hereditary and not-at-all-related to learned behavior.

It is from Part v, just after the graph, in his review of The Hungry Brain. by Stephan Guyenet.  There is more detail about this particular example immediately after. An environment may influence behavior, such as BMI or violence or anxiety, yet it does not affect everyone equally.  And the not equally is often genetic. Because there is variety of response, the people who do "best" by some measure are likely to get smug, believing that they worked harder or were more righteous or have a better attitude, but they may just have been wired better right from the start. It is not good to give yourself credit for your heredity. 

As usual, Suskind goes on too long, trying to be thorough.  Still, it is very good, weighing one side against another and looking for weaknesses in his own argument. Overall, it is discouraging about long-term (meaning five years, not a few months) serious weight loss (meaning normal weight, not "a reduction of 10% of weight.")

Also, I loved his first sentence of Part vi.

Lest I end on too positive a note, let me reiterate the part where happiness is inherently bad and a sort of neo-Puritan asceticism is the only way to avoid an early grave.

As BMI was brought up, creating a rabbit-trail we all want to go down, I should include a link to another article about the mysteries of obesity, which includes a disclaimer about using BMI. 


Narr said...

That's fascinating and plausible in the main but--

BMI is bogus and has no real scientific basis or utility as applied to individuals. NPR (of all sources!) actually has a pretty good takedown of the concept and its misapplication.

To me, BMI is analogous to the 'normal' human body temperature of 98.6. My temperature has never been 98.6 when tested except by coincidence--usually it's lower. If we treated temp like we do BMI, then a lot of us would be using drugs to raise or lower our number to the "right" one. (I had a friend, no dummy, who got it into his head that "Norm"--the old Bureau of Standards statistical model of the average American male--actually represented some ideal of body proportion.)

That's all for now--I forgot what else I was going to say, and need to walk the dog. Maybe I'll recall.

Cousin Eddie

Texan99 said...

It's also easy to make the mistake, though, of imagining that because something is easy for other people, we're entitled to insist that it be easy for us, too. If we have a weak spot, whether it's for genetic or other reasons, it's up to us to take it into account, not just give in and blame propensities.

Narr said...

Ach, what a dunderhead I am.

The other matter was the Anthony book on prehistory--it's really excellent, not too abstruse. I have more knowledge of the linguistic background and theory than the archaeology, but they seem to fit neatly enough so far.

Thanks for the recommendation!

Cousin Eddie

bs king said...

@Cousin Eddie - I'm not sure bogus is quite the right word. BMI is actually largely correct if it tells you that you are obese, a little shaky in the overweight range, and overly optimistic if it says you are fine.

I did a post with the actual numbers on this a few years back, including the mortality implications for each level:

Christopher B said...

Another angle that is similar to Tex's take is that it might be very possible, at least in the First World, to adjust your personal environment to better fit your genetics. It's pretty likely that one size doesn't fit all. Insisting that some plan is universally applicable could be very detrimental, especially when combined with an equally obsessive focus on a single attribute as indicator of what is 'best'.

Assistant Village Idiot said...

@ Narr - At the beginning of a lead-in article I was sent about obesity, which I should have also linked, the author parenthetically notes that body fat measure is better than BMI, but so many studies use BMI as their marker that it is convenient to use it anyway. I will put it here, but also insert it into the OP.

As for David Anthony, he is now working at Reich's lab at Harvard, doing more cool stuff.

@ Christopher B - yes, absolutely. We all sort of do that by trial-and-error, stumbling into places that fit better. Yet I think we could help oursleves - and our children and our students - by doing that more intentionally.

Narr said...

The BMI triggers me--it has been weaponized against people who don't adhere to the current cultural norms of health and beauty.

I can understand that it gets used a lot because it's convenient and seems intuitively right, but it's not that useful in regard to an individual. That's all.

David Anthony was featured briefly in a NOVA show--"The First Horse Warriors"--that I chanced on a few weeks ago.

Cousin Eddie

stevo said...

I think genetics are everything. I eat everything and always have. I still wear the same size jeans I did at 16. And I claim no virtue. Just lucky.