Why don't people understand my intentions?
Oh, ha ha. Wake up. This is important.
Yes, it's a dense academic tome with 19 pages of footnotes. You can handle it. And you should, because there are three extremely important messages in this book.
First, the authors make a pretty good case that we know a lot less about the causal relationships in human health than we think we do. The definition is important there: medicine has been very effective at discovering what makes people sick (and how to make people not sick), but it's much harder to even establish what it means to be well.
We know a lot about correlations, but not a lot about what actually causes "health," or what definitively causes "lifestyle" illnesses (whatever those are). The authors do a good job of pointing out the methodological problems in this area: those darn Human Factors Boards won't tend to let you lock up big samples of people and mess with their diets and activity levels, so you're left with a lot of self-reporting and "best guess" research. This tells us a lot of things, but it doesn't establish causality.
What's even worse, we have a lot of people making completely unsubstantiated claims because of this lack of data. Let's take that truism that "we're less active now than we were 50 or 100 years ago." Well, we don't have particularly good data on current activity levels, and for 50 or 100 years ago, we pretty much don't have any. Lots of people believe this statement, but it's essentially speculation, not science.
This worries me, and it should worry you, because it's a bigger social phenomenon. I'm concerned that our high school and college students aren't required to learn enough logic, and we're not equipping ourselves to evaluate the arguments which we see only in a distilled pop culture form. If we don't teach ourselves to follow up on the 20-second news blurb, how can we ever make good decisions?
The second point, as I've written before, is that the intersection between body aesthetics and ideology is dangerously toxic. I'm not saying that it's wrong to admit that you like looking at some body types better than others. I'm saying you're in a bad intellectual neighborhood when you let yourself mistake appearance for personality.
Gard and Wright are pretty good about criticizing both sides of the street on this one. Most people will be familiar with the modern trope that fatness is a sign of moral decay. (And it is a modern construction.) They also do a good job of criticizing the CSPI/Fast Food Nation folks, who seem to believe that it's The Big Bad Corporation that makes us fat. Between the two groups, it seems that everyone who doesn't fit an idealized body type must be either lazy to the point of evil, or too dumb to be responsible for themselves. (Because, after all, Kate Moss is such a good role model.)
(I'm reminded of an old parody of Cliff's Notes I saw back in high school. The study questions for Julius Caesar included this: "Yon Cassius has a lean and hungry look." Do you have a friend with a "lean and hungry look"? Give him a sandwich before somebody gets hurt.)
The problem is that these beliefs do leak into our science and public policy. That brings us to point number three: science is performed by humans, which means that there's an inextricable social element to it.
I said this to one of my colleagues, and he reacted as though I were a beret-wearing, Gauloise-smoking postmodernist. So don't get me wrong; I'm a big fan of the scientific method. Science, in the long term, builds on what is demonstrably true and leaves behind what is not. Still, human beings have an incredible ability to find what they're looking for. Especially when that's what the Tenure and Promotion Committee is looking for, or the grant agency is looking for, or the publisher is looking to sell, or the CEO thinks is profitable, or the current administration can use to win votes. Or just because it grinds your axe.
To pretend that's not true, as if scientists go off to some socially isolated clean room where The Truth always wins out, is a potentially deadly mistake, especially in the short run. Basic Science, after all, is in a big knowledge web with Engineering and Policy, and the only thing worse than leaving them all tangled up is to try and pull them apart. Better to acknowledge that the evidence says they are related, and try to tease out the relationships from there.
It's what a Scientist would do.