Programmes, partners, smart scales, doctors, teenagers and the jeans that do the same job

Every reader has a reason the general advice doesn't quite fit. Here are the ones I'd expect, each in turn.

You're in a weight-loss programme that asks you to weigh. Then weigh, and the average in chapter 17 is your version. The trials in chapter 6 are on your side, and the programme's weekly weigh-in, if it has one, is already a weigh day with a line attached. What this book asks is only that the daily number, if you take one, goes into a notebook or an app unread, and that the figure you react to is the week's. If the programme wants you to react to the daily number, I'd ask them why, given that Madigan's meta-analysis found no difference between daily and weekly instruction.

Your partner weighs every morning and says the number out loud. You can't take their scale away, and you shouldn't try. You can take yourself out of the room. Ask, once, plainly, for the number not to be said, because you're trying to stop it running your morning. Most partners will manage that. If they weigh in the same bathroom at the same time and the scale is out on the floor, your break may need the scale to live in a cupboard they agree to. That's a conversation and not a fight, and if it turns into a fight, the fight isn't about the scale.

Your scale reports body fat, water and muscle. It does so by passing a small current through you and estimating from the resistance, and the estimate moves with hydration, which is to say with everything in chapter 3. A body fat figure that changes by a percentage point overnight has measured your water, not your fat. Treat every number the scale gives you the same way, as one point in a column, or switch the extra readouts off, which most of them allow. A scale that gives four numbers to swing on is four times the problem.

A doctor has told you to lose weight. That's a real reason to know whether your weight is moving, and the weigh day is your version, with the line shown to the doctor at the next appointment rather than the morning's figure. The NHS page on overweight says that losing even a small proportion of body weight can improve health. It doesn't say to weigh every day, and nothing in the advice needs you to.

There's a teenager in the house. The five-year study in chapter 9 found that frequent weighing in girls predicted unhealthy weight control and binge eating years later, and its authors say that programmes aimed at adolescents should avoid encouraging it. So the scale in the cupboard is a good idea for reasons beyond you, and so is not saying your number out loud, and not commenting on theirs. If a teenager is weighing often and the mood seems to depend on it, the NHS eating disorders page is worth reading with chapter 23 in mind.

The jeans have taken over. You put the scale away and found yourself trying on the same pair every morning, and the button became the number. This is the habit changing costume. The answer is the same. One pair, tried on once a week or not at all, and the other mornings the clothes chosen for the day and not as a measurement. If you can't do that, it's a sign that the break needs to be a break from measuring, not from the scale, and chapter 20's list of slow measures is where to go.