Should You Weigh Yourself Every Day?

The usual advice about bathroom scales is to stay off them. Weigh yourself once a week at most, the reasoning goes, or the daily ups and downs will get into your head. For some people that’s exactly right, and we’ll come back to who.

For people trying to lose weight or keep it off, the research mostly points the other way. Weighing often tends to help, and a well-run trial found it didn’t make people feel worse. The catch is that you have to read each number as one point in a trend. A single morning’s reading tells you very little about fat.

What Happened to the Daily Weighers

In a 2015 trial, 162 adults who wanted to lose weight were split into two groups for six months. One group got a smart scale, an instruction to weigh themselves every day and simple feedback on how they were doing. The other group didn’t. By the end, the daily weighers had lost significantly more weight and had taken up more of the habits that researchers count as weight-control behaviours.

The team also measured the thing people worry about. Daily weighing did not raise depressive symptoms, and it didn’t increase binge eating or other measures of disordered eating. That’s one trial, in people who had signed up to lose weight, so it can’t speak for everyone. It does make it hard to argue that stepping on the scale every morning is harmful by default.

Steinberg, D.M., Bennett, G.G., Askew, S. & Tate, D.F. (2015). “Weighing every day matters: daily weighing improves weight loss and adoption of weight control behaviors.” Journal of the Academy of Nutrition and Dietetics, 115(4), 511-518.

A systematic review published the same year looked across the wider research on self-weighing and found the same pattern again and again: more frequent weighing went with more weight lost and less of it regained later. An association like that has an obvious alternative explanation, which is that people who are doing well are happier to look at the number. In the trial above, chance decided who weighed every day, so that explanation doesn’t hold there.

Zheng, Y. et al. (2015). “Self-weighing in weight management: a systematic literature review.” Obesity, 23(2), 256-265.

Why the Number Jumps Around

Swings of 1–2 kg from one day to the next are normal, and very little of that is fat. A kilo of body fat holds far more energy than one big evening of eating could add, so an overnight jump is almost always something else.

Mostly it’s water. A salty takeaway makes your body hang on to extra water for a day or two. Your muscles and liver store carbohydrate as glycogen, and glycogen holds water with it, which is why a pasta-heavy weekend tends to show up on Monday and why the first week of a low-carb diet looks more impressive than it is. Food and drink that haven’t left your gut yet count too. Many women also retain more water in the days before a period, enough to hide a week of steady progress.

Weigh at the same time every day, which for most people means first thing in the morning, after the toilet and before you eat or drink anything. Use the same scale on the same patch of floor, in roughly the same clothes or none. Then average each week’s readings and compare the averages. If they keep drifting down over two or three weeks, you’re losing weight, whatever Wednesday said.

Measure Your Waist as Well

The scale also says nothing about where your weight sits. If you’ve started strength training, you can lose some fat and gain some muscle while the number barely moves. Fat stored around the middle is the kind most closely tied to heart and metabolic problems, and a tape measure picks that up where a scale doesn’t.

A 2012 meta-analysis compared simple body measurements as screening tools for cardiometabolic risk. Waist-to-height ratio did better than waist circumference on its own, and better than BMI.

Ashwell, M., Gunn, P. & Gibson, S. (2012). “Waist-to-height ratio is a better screening tool than waist circumference and BMI for adult cardiometabolic risk factors: systematic review and meta-analysis.” Obesity Reviews, 13(3), 275-286.

In 2022, NICE, which writes health guidance for England, added the ratio to its advice with a target you can check at home: keep your waist to less than half your height. If you’re 170 cm tall, that means under 85 cm. Measure halfway between your lowest rib and the top of your hip bone, after a normal breath out. Waists change slowly, so once a month is plenty.

Some people are better off skipping the scale altogether. If weighing yourself makes you anxious, or you have a history of an eating disorder, a trial average says little about how it would go for you. Use the tape measure instead, or nothing at all. Plenty of people look after their health without knowing what they weigh.

Weigh-ins are free to log in Lamplit, and we built the weight-goal card on the Health page, under Analytics, around the same idea as this article. It shows no pace at all until it has at least three weigh-ins spread over at least seven days. After that it describes your current pace, and it never promises a date you’ll reach your goal. Weigh in tomorrow morning, add a few more readings over the week, and look at the trend before you react to any single number.

Start logging your weigh-ins in Lamplit. It’s free, and your pace appears after three readings spread over a week.