Friday, 23 March 2012

Junk Science that supports Health at Every Size is still Junk Science

A few months back, over at Big Fat Blog there was a report on this study.  The study was basically examining four 'healthy' habits (moderate drinking, not smoking, 'exercising' and eating 5 plus fruit and vegetables) and the BMI, and then doing an analysis of risk of death.  DeeLeigh from BFB summarised its findings like this:
Two things really jump out at me. First, the more healthy habits we have, the more our life expectancy matches the life expectancy of thin people with the same habits. When we've got all four, the gap is pretty much closed. Second, it's only the fat people with no healthy habits who have a dramatically reduced life expectancy in comparison to thinner people.

This is a strong confirmation of what HAES advocates have been saying for years
It's bullshit.  Of course it's bullshit.  This study has exactly the same errors as all the other studies which people on fat acceptance blogs have picked apart and chanted "Correlation does not prove causation" at.  The most glaring of which is (as always) that it does not control for class. You cannot say anything meaningful about people's bodies or lives if you don't take into account the way resources are distributed in society.

I've always felt slightly uncomfortable about the way scientific studies are used for the cause of fat acceptance. I've always felt it conceded too much ground - by spending lots of energy arguing that fat isn't necessarily unhealthy, we're conceding the conclusion that if fat was healthy fat hatred would be justified.   But I can see that given the amount of junk-fat-hating masquerading as science there is out there debunking is useful work.  But if debunking is going to work as a persuasive factor, or (more importantly in my opinion) a way of figuring out how the world works, then people engaging with scientific studies have to be absolutely disciplined and committed to engaging with the literature as it is.  Just reposting one article that agrees with your pre-conceived views without engaging with the critical thinking that you would if it disagreed undermines that project.


That blog post was the first thing that came to my mind when I read the post and skimmed the article. But then I read the article in more detail and I became outraged on a whole new level.  Because in the article itself they provide how they'd defined exercise:
Level of physical activity was determined according to the frequency of participation in leisure-time physical activities within the previous month.
 There is no justification for this definition in the article.*

I actually lose it at this point and can't form any coherent thoughts.  You can't measure a subset or something a pretend you've measured the whole thing.  You can't claim to do one thing, when you're actually doing something else.  You can't just wave away the word 'leisure-time' as if it doesn't exist.  Except apparently you can - in a peer-reviewed journal.

I want to know how wide-spread this is? How often in peer-reviewed articles, advice given to doctors, information passed on to us all have they told us that 'exercise' has a particular effect when they've measured 'leisure-time exercise'.

I was vaguely aware that workplace exercise did not quite fit the chirpy model put about in videos like this one.  Partly I just knew this from studying the history of work - work that requires exercise wears bodies out - it's nothing like the experience of exercise that people get from the gym (this article about working in a warehouse for internet shopping is an important reminder that there are now new forms of work that require body destroying exercise).

The most obvious point we come against is class (they also, surprise surprise didn't control for Socio-economic status in this article).  Are articles about leisure-time exercise actually measuring the effect leisure time that you can use for yourself?    The experience of physical activity as part of paid work is qualatatively different from leisure time physical activity - when you're in paid work that you're going to have to do day in day out, you have to conserve energy and conserve your body.  Also people who can do leisure-time physical activity probably aren't facing body-destroying physical labour in their jobs. 

this article has long fascinated me (warning Ben Goldacre is a fat-hating douche at the beginning).  It tells of a study of hotel cleaners, many of whom described themselves as doing no exercise (which shows how deeply the false equivalency of leisure-time exercise and exercise has worked into people's self-defintion).  In one hotel they told the workers specifically that the work cleaners were doing (which is after all hard physical labour) was exactly the sort of exercise that doctors recommend.  The group who were told that saw all sorts of health benefits over the next month.  But the question that I've always wondered is - why didn't they see themselves as doing exercise?

I was recently hanging round with a five-year old who is always running around like a young spider-monkey and she was talking to herself about 'exercise' and describing some of the things she was doing as 'exercise' - and it was clear that she'd just started school and been told about the importance of exercise and she was trying to figure out what 'exercise' was - what part of her constantly moving around counted.  Because 'exercise' is not quite synonymous with physical movement - and a five year old need to figure that out - even if peer-reviewed journals only tell us so in their methodology section.

* There may some justifications in the articles that are cited, but I couldn't access any of the cited articles in the relevant section.  I'd love to hear from people who can if there is a justification if you follow the references.


Psycho Milt said...

It's not "science," for all that the practitioners like to pretend it is. It's actually "social sciences," a very different beast consisting of the assemblage of correlation = causation errors in support of a previously-held opinion. That the media treat it as science is extremey annoying.

Anonymous said...

If you think social science is all about "correlation = causation" you clearly don't know what social science is.

Psycho Milt said...

The definition was tongue-in-cheek and somewhat cynical. Doesn't alter the fact that epidemiological studies looking at effects of diet on health are social science, not science.