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There’s a lot of buzz on the list serves about a new website that just launched called Spurious Correlations. The site reports a new “correlation” each day. For example, the site points out that the correlation in Maine between eating margarine and divorce is over 99 percent. Does this mean that Maine residents who want to maintain their matrimonial bond need to switch right on over to butter? I mean 99 percent seems pretty darn compelling, right? There are lots of other important correlations listed on the site including:

Per capita consumption of mozzarella cheese and civil engineering doctorates awarded–95%

Honey producing bee colonies and the marriage rate in Vermont–93%

US domestic price of uranium with accidental poisoning by alcohol–97%

Spurious Correlations is a wonderful tool for demonstrating that oh so important axiom, “correlation is not causation”. This means that just because two things tend to happen together does not necessarily mean that one causes the other. They might have a third agent which is causing them to happen together or they might have no relationship to one another whatsoever outside of a random statistical similarity.

I think that Spurious Correlations is a fascinating site. I’ve spent way too much time tooling around in there. But I also think it is an important tool for helping us understand our world. Because so many of the people writing and talking about science on websites and blogs, on television, in magazines and newspapers get this relationship between correlation and causation so very wrong. I think in some cases the writers and speakers don’t understand the difference. But in other cases, I think the writers are very clear about the difference and simply report correlation as causation because it makes better headlines or sells more product. Take this blog post for example. I don’t have any proof that buying margarine causes a single divorce in Maine. But I imply that there might be a cause by asking the question in the headline: “Does Eating Margarine Cause Divorce”? It’s easy to see why I did that. “Per Capital Margarine Consumption in Maine Closely Correlates with Divorce Rate” just doesn’t have the same ring to it. But I think most people would agree that even though butter tastes a whole lot better, eating oleo is unlikely to be the cause for divorce. Either something else is going on to connect these two statistics, or they are completely unrelated. So the difference between correlation and causation here is pretty easy to spot.

But what about the correlation between the total number of computer science doctorates awarded and total arcade revenue. These two facts correlate at over 98 percent. And it would be pretty easy to formulate a theory about how these two facts are related. Maybe when there are more computer science students, it means there are more nerds that love to play arcade games. Maybe more computer science doctorates means there are more nerds qualified to design and implement great arcade games. With just the tiniest whiff of a potential relationship, our minds naturally leap to find ways that one of these facts could cause the other. But there remains the very distinct possibility that there is no causal relationship whatsoever between these two statistics.

I find this particularly relevant in our current national hysteria over obesity. It seems every week there is a new study claiming that this thing or that thing causes obesity. And everywhere you look you see “proof” that obesity causes this problem or that problem. But I think it is important for us to keep our wits about us and take a look whether these studies can sufficiently demonstrate that two correlated facts have a causal relationship. For example, people are spending more time in front of computer screens than ever before. Some have suggested that increased screen time causes obesity. But do we know that is true? Or are these things simply happening at the same time. We also have more 24 hour gyms than in the previous century. Is it reasonable to suggest that the increase in 24 hour gyms causes obesity? Maybe dieting causes obesity, or exposure to certain plastics? Heck, based on the correlation, one could easily suggest that talking about obesity increases obesity levels! And how about the rise in medical insurance costs and the rise in obesity. Does a larger number of fat people cause higher insurance rates or is there something else going on? The question of the rise in health insurance rates is detailed and complex but how many people have simply jumped to the conclusion that the fatties are making their monthly premiums higher. How many of us take the time to understand: the only way that we can prove that one thing causes for another is through careful experimentation where as many other variables as possible are ruled out and a causal agent is ultimately found.

So when you come across studies that demonstrate a relationship between say obesity and heart disease or obesity and cognitive function, I urge you not to just jump blindly onto the causation train. Ask yourself a few questions:

Has this study adequately controlled for other causal factors? Has it controlled for diet, physical activity levels, socioeconomic status, access to good healthcare, education, etc.?
Has this study identified a causal link that demonstrates why these two things are happening at the same time?
Is it possible that these two statistics are simply randomly related with no causal relationship whatsoever?

That is not to say that correlation never go together. All causal relationships are also correlations. But not all correlations contain causation. These are important facts to keep in mind the next time you read a headline screaming about the causes of obesity or harm caused by obesity–or the next time you decide to buy margarine in Maine.

Love,

Jeanette (AKA The Fat Chick)

P.S. Want to go on a virtual vacation? Ragen and I over at the Fit Fatties Forum are launching Virtual Vacations that allow you to exercise while virtually visiting some of the world’s most fabulous cities!

So very often these days we hear that the world has deemed to help the portly because they so desperately need help and the world is being nice–and stuff. Millions upon millions are invested in trying to prove that fat people are unhealthy, and if they would just eat a little less and move a little more, all their problems would be solved, everybody in the world would be healthy, and good, quality health insurance would cost everybody $1. The fact that despite the millions of dollars spent, nobody has been able to prove these or demonstrate any way to make this magical weight loss happen on all but a fleeting and temporary basis doesn’t seem to deter anybody from testing this hypothesis again and again.

And even when the proof is not available, or indeed the available evidence says that your “weight intervention” causes negative effects and makes people fatter current policy seems to involve simply ignoring those pesky little facts.

Take the current practice of weighing and measuring kids at school and then sending home “BMI report cards”. Despite showing again, and again and again that shame doesn’t make kids thinner or healthier, showing that shame causes kids to engage in more unhealthy behavior, that shame makes kids fatter, we still do this. Why? The National Eating Disorder Information Center issued the following statement regarding BMI testing in schools:

What the American Academy of Pediatrics (AAP) seems to be ignoring in its advocacy of weighing and measuring the height of schoolchildren is the risk it carries not just to increase body-based bullying from student’s teachers and peers, but the risk to children’s developing self-stigma and poor body image.

Body-based bullying continues to be the most common cause of bullying in youth. 29% of girls and 15% of boys are already teased about their weight at home. By grade seven, up to 30% of girls and 25% of boys are teased by other students. Poor body image has been found to stop youth from engaging in social, academic and physical opportunities. It limits willingness to express an opinion. In perpetuating focus on body shapes and sizes rather than on encouraging health providing attitudes and behaviours in children regardless of size, what are our schools (and public health) teaching?

However, it seems that plans to do BMI testing and BMI report cards in schools is continuing throughout North America.

This also reminds me of another recent situation I had recently reported. Blue Care of Michigan is still touting the positive results of their “enforced march” walking program for fatties despite the fact that there is no evidence at all that those who participated either lost weight, or had any positive health outcomes associated with the program. They apparently did nothing to track the original fitness level of the plus-sized participants and had no idea whether or not these folks were already active. They just told these people that unless they wanted to pay an additional $2,000/year they had to participate. They also forced those who participated to either be a member of Weight Watchers or wear a monitor which counted their steps during the day. Just like a prisoner, they were forced to wear a physical implement on their bodies that told their insurance overlords what they were doing throughout the day. Just because their BMI is over 30. They declared this project a success even though nearly 1/3 of the 12 percent of participants who bothered to respond to the survey said they hated the program and found it coercive. For more information, you may wish to read this article from my friend and colleague Jon Robison.

Throughout all this rhetoric about making fat people into “healthy thin people”. Throughout all this spending on proving that fat people can become thin people on more than a very temporary basis and that making fat people into thin people will make them healthy there is one thing continually missing and that thing is proof.

When the available evidence points to the opposite of the fat people can become thin people, or fat people can’t be healthy people or fat kids just have ignorant parents rhetoric, the powers that be either request more money to re-test the hypothesis or simply ignore the inconvenient facts.

You may have heard of iatrogenic effects in medicine. Dictionary.com defines them as: (of an illness or symptoms) induced in a patient as the result of a physician’s words or actions, esp as a consequence of taking a drug prescribed by the physician.

And good old Dictionary.com also defines iatrogenic as relates to social welfare: “(of a problem) induced by the means of treating a problem but ascribed to the continuing natural development of the problem being treated”.

Some experts have suggested that the “obesity crisis” is a textbook example of iatrogenic effects in both medicine and social welfare. But I wonder if the “obesity crisis” isn’t responsible for iatrogenic effects in the economy as well. If the response to the mounting pile of evidence that “diets don’t work” and “shame doesn’t work” and “fat people can be healthy” is always, “let’s pay for more tests” or “let’s do the weight loss junk but try harder this time” the obesity crisis will continue to be very, very expensive.

But I think the treatment for the economic effects of the hysteria surrounding the “obesity crisis” may be as simple as this. Demand proof. If your insurance company wants to put you on a walking program without doing an intake of any kind or presenting any data regarding the efficacy of the program, demand proof. If your kid’s school wants to measure their BMI along with everybody else’s and send home a BMI report card, demand proof that this makes kids happier or healthier. It’s not easy. It’s not fun. But the rights of fat people to enjoy life, liberty and the pursuit of happiness demands that we, the fierce fat folks, demand proof.

Love,

The Fat Chick

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