The comma in the title is there for a purpose, because I wanted to talk about the similarities between the two fields, not their supposed connection. Judith Curry's Climate etc website had an excellent piece on those similarities, and that prompted this post. But as I read the Comments section I came across exactly what I didn't have in mind. It is priceless:
If you enter "obesity and global warming" into Google, you obtain 1,100,000 responses. Typical responses in the queue are: (1) Is Obesity Causing Global Warming? A new study has suggested that obesity is affecting the planet … by raising carbon emissions …; (2) Do Obese People Aggravate Global Warming? - ABC News; (3) Scoop: Burning the Fat: Obesity and Global Warming, a study in the latest issue of the International Journal of Epidemiology by Phil Edwards and Ian Roberts plays out a grim scene: a world of overweight …; (4) thinner is better to curb global warming, study says-CNN.com; and there are thousands more like this.
No, what I really had in mind is this: the the field of nutrition, like that of climate science, is not one where you can design nicely controlled tests of various hypotheses, so that what we get are only lightly-substantiated warnings that the news media like. 'If it bleeds, it leads' … that sort of thing. I'm old enough to remember how butter became a no-no: we should all move to margarine. Red wine and red meat were bad for you, then good for you. Diets were everywhere, and still are. My inheritance is largely Scots, and my forbears were on the whole skinny - or 'slim', if you want a nice word. I've never had to worry about my weight, enjoy physical exercise, played a lot of sport, and pretty well eat what I like. Even better, I stop eating when I've had enough, and stop drinking after two glasses. I don't have to force myself; it just happens.
So I've looked at all these nutrition news items, over the 55 years since I married, with interest but on the whole without personal alarm. The Scots inheritance, however, cuts both ways: I've had a lot of skin trouble, with one large melanoma and many, many visits to the skin specialist to deal with incipient cancers.
Now Judith Curry looked at an article in the New York Times by Gary Taubes, and you can read it here. I don't remember more than one or two of the kids at my school being even overweight, and though my best friend was known as Fatty Conway he got this nickname because he was just a bit more amply provided than the rest of us. Nor were there lots of overweight students at university. Taubes makes much the same point about the USA: In 1960, fewer than 13 percent of Americans were obese, and diabetes had been diagnosed in 1 percent. Today, the percentage of obese Americans has almost tripled; the percentage of Americans with diabetes has increased sevenfold. I first went to the USA in 1965, and noticed at once that were indeed quite a lot of really overweight people, and that Americans seemed to just eat much more than we did. Everything in the food department of a supermarket was bigger, like ice-cream tubs, jars of anything, and packets. Sugar seemed to be in almost everything, even supposedly 'savoury' items.
Taubes says that more than 600,000 articles have been published on obesity and diabetes, and that this should have brought some clarity as to the causes of it all. But no, the situation apparently just gets worse and worse. Taubes says that these 600,000 articles are the noise generated by a dysfunctional research establishment. Because the nutrition research community has failed to establish reliable, unambiguous knowledge about the environmental triggers of obesity and diabetes, it has opened the door to a diversity of opinions on the subject, of hypotheses about cause, cure and prevention, many of which cannot be refuted by the existing evidence. Everyone has a theory. The evidence doesn't exist to say unequivocally who's wrong.
And why? The only way to test these hypotheses is through the use of specific, randomised, controlled clinical trials. Because the hypotheses are ultimately about what happens to us over decades, meaningful trials are prohibitively expensive and exceedingly difficult. It means convincing thousands of people to change what they eat for years to decades. Eventually enough heart attacks, cancers and deaths have to happen among the subjects so it can be established whether the dietary intervention was beneficial or detrimental.
Now no drug company stands to make much if any money in these areas, so there's no interest from the private sector in funding trials, while for the public sector - the government - they look like extraordinarily expensive endeavours that will take decades to produce results, which might be wrong even then. So nutritionists study rats and hope the results apply to us, or study humans for a few weeks or months and hope that the results apply to decades. Or they look at whole populations where particular food regimes operate and look at the general frequency of various diseases, and hypothesise causal links.
It's a good piece, and a quick read. Does any of this story strike a chord for you about the field of climate science? It did for Judith Curry, and you can read her take on it here. I agree with her that there are many parallels. See what you think.
As for causes: I offer this historic overview. We have moved from being a physically active population to a sedentary one, where exercise has to be programmed into our lives rather than occurring naturally, while we are now rich enough to be able to afford to eat and drink for comfort rather than to enable us to be productive. No, I'm not proposing a long trial …