How to think statistically (about dieting)
There are lots of ways to get statistical thinking wrong, not so many ways to get it right. Here’s a series of examples from wrong to right:
- I did this, and it’s not a “diet,” it’s a lifestyle change, and it works for me!
- I know people who live or interact with the world in a certain way, and it seems to work for them! After all, French women are thin. We should all do what they do.
- There was a study of volunteers, and for the people who stayed in the study to the end, they lost weight doing such and such lifestyle change!
- There was a study of volunteers, and they tracked people down who tried to leave the study, and the average weight gain was still real, among the people they found!
- There was a study of doctors giving advice or enrolling people in programs to help overweight people lose weight, and 97% of people lost no weight and plenty of people gained weight, maybe even more than half.
What I’d love is for people to understand how much difference there is between a personal experience (1) and advice we’d have on public health (5).
Here’s the golden standard: if you can come up with something to tell Medicare about how to have a population of morbidly obese people become a population of regular weight people, then you win. Otherwise, if you’re tempted to tell me about a lifestyle change that worked for you, please don’t, because that’s not statistical.
Also, I’d like a word about the theory that with enough discipline and willpower, anyone can lose weight. I think it’s fair to say I have discipline and willpower. In fact, I’m a fucking poster child for them. I wrote a Ph.D. as one of few women in a male-dominated field. I wrote a book or two. I’ve had three kids and I’ve never struck one of them in anger. In fact I’m pretty nice to people most of the time, even though I’m relatively often filled with rage at the unfairness of the world. That’s hard. It takes willpower.
I even ran a sprint triathlon at 275 pounds, really fast, which took months of ridiculous training. Also, I know all about healthy habits, I don’t eat “emotionally,” just when I’m hungry, and I love brussel sprouts and other healthy foods. I just get really fucking hungry, often.
Readers, I’m the fucking center of the disciple in willpower universe over here.
Given all of that, if anything I’d argue my willpower is one reason I’m so heavy. When I was 22 or so, I went on a fat-free diet, on the advice of my doctor, that fucked me up; I lost 30 pounds but then gained something like 75. I think I messed up my insulin resistance. In fact I believe that also happened to me on my first starvation diet when I was 14.
I’m guessing I’d be thinner if I’d had less willpower, in other words. I wouldn’t be better off, though, because I kind of like my books and my Ph.D. and my kids who don’t fear their parents.
Anyway, from now on let’s talk statistically, shall we?