"It's only a number, I can handle it"

You know the arguments in chapters 3 to 5, or you knew a version of them already. You know water goes up and down. You've told yourself on a bad morning that it's probably water. And it hasn't helped, or not much, because the swing arrived before the argument did and outlasted it. This chapter is about why knowing doesn't stop it, so that you stop blaming yourself for being unable to think your way out.

Ogden and Evans ran an experiment in 1996 that I find hard to forget. They took 74 people of ordinary weight, measured their mood and self-esteem, weighed them, and then showed each one a fictional height-and-weight chart that placed them, at random, as underweight, average or overweight. Nothing about the person had changed. The number on the scale was their real weight. Only the label on the chart was invented. The people told they were overweight showed a rise in depression and a fall in self-esteem, measured minutes later. The ones told they were average improved on both.

Think about what that shows. A number that a person knows is being compared against a chart they've never seen, that has no bearing on their actual body, moved their mood in the time it takes to read it. If a made-up label can do that to people who weren't even worried, an actual number can do it to someone who steps on every morning specifically to find out. The swing isn't a failure of understanding. It's what a number about your body does to a person, before understanding gets a chance.

The authors were writing about clinics, and their point was that weighing patients and comparing them to charts might not be as harmless as everyone assumed. I'd extend it to bathrooms. You aren't weak for reacting. You're doing what 74 ordinary people did in a room in the nineties.

This matters for what comes later, because it rules out one plan. The plan where you keep weighing daily and just decide not to mind. You can't decide not to mind, or not reliably, and every morning you try and fail is another morning where you feel you've failed at something, which is a second swing on top of the first. The options in chapter 17 all work by changing what the number is, or when you see it, rather than by asking you to feel differently about it.