Get the Fat Out of Your Brain

The people behind the Great Brain Robbery follow a lot of blogs and folks on Twitter. Brain-talk is a rich field, with lots of research, many different point of views, and thousands of theories all coalescing in a miasma of opinion, explanation, interpretation. Sometimes we see things we disagree with. Sometimes we feel like this casual blogging stuff sends the wrong message.

For example, a blog post we found today that asserts: “The more a woman weighs, the worse her memory.” We’re not going to link to this blog, but we’re going to take it apart. First, the study that found this correlation between BMI increases and memory test decreases only studied women ages 65 to 79. That’s not “women” in general, so the above assertion is spurious at best.

Then there’s the use of the BMI, a terrible way to classify anything except unrelated metrics. Take a person’s weight in kilograms and divide by the square of their height in meters. The taller you are, the more you weigh, and if you are not tall enough to weigh as much as you do, you’re fat. Except that taller people will weigh more than the a simple two-metric function will predict, making them “fat,” and the BMI doesn’t, obviously, account for what gives a person mass in the first place. Body builders are fat, and people who suffer from anemia are skinny: who’s healthier?

Who’s dumber? Because when bloggers start throwing around sentences like “the worse her memory,” that’s a judgmental statement. And this blogger later says “Remember, everything the brain does affects memory (and everything affecting memory affects the brain).” Therefore, if you’re a woman who weighs too much, expect to have decreased brain function, according to this blogger.

The blogger doesn’t bother to show the causative relationship between weight gain and memory dysfunction, but does say that another study showed that people who had bariatric stomach by-pass surgery showed mental improvements. This same blogger, in the past, has talked about the very positive effects happiness has on memory. Who, in this overly-critical society, wouldn’t be happier to be, finally, skinny?

Does gaining weight effect memory? Or does not exercising effect memory? The blogger says “Though exercise doesn’t do much to cause weight loss, it has many other benefits… that can directly benefit memory.” Did this study of older women control for the ones who, despite having a higher BMI were exercising regularly?

How about this: let’s stop using inadequate tools to focus on vaguely correlative measurements and making painfully obvious conclusions.

As you age, good health is important for maintaining brain function. We’ve known that for centuries.