If you are trying to lose weight and the scale does not upset you, weighing yourself daily and looking at the weekly average is the approach with the strongest research behind it. Weighing once a week also works, and it is what NIDDK describes for structured weight-loss programmes. What matters more than the exact frequency is that you weigh under the same conditions and judge progress by the trend, not by any single number. If weighing makes you anxious, or you have a history of disordered eating, it may be better not to weigh yourself at all.

Here is what the studies found, why your weight jumps around from one day to the next, and how to set up a routine that gives you useful information.

What the research says about daily vs weekly weigh-ins

Daily weighing in trials

In a six-month randomised trial in Obesity (Steinberg and colleagues, 2013), 91 adults with overweight were split into two groups. One group got a connected scale, a weight graph online and weekly emails with feedback, and was asked to weigh every day. The control group started later. After six months, the daily-weighing group had lost about 6.6% of their body weight on average, compared with about 0.4% in the control group. They weighed on about six days a week and ate fewer calories per day. Participants also rated daily weighing positively.

A follow-up analysis in the Journal of the Academy of Nutrition and Dietetics (2015) looked only at the people in that intervention group. Those who weighed every single day lost on average about 6 kg more than those who weighed on most, but not all, days, and they had taken up more weight-control habits. This was a comparison within one small group (47 people), not a new randomised trial, so it shows an association rather than proof that the seventh day is what made the difference.

What reviews say

A systematic review in Obesity (Zheng and colleagues, 2015) looked at 17 longitudinal studies of adults in weight-loss treatment. Regular self-weighing was associated with more weight loss and was not associated with depression or anxiety in those groups. The review also noted that the size of the effect and the definition of “regular” (daily, weekly) varied a lot between studies.

A second review, in Current Obesity Reports (Pacanowski and colleagues, 2015), took a closer look at psychological effects. It found a more mixed picture: in some studies, frequent weighing was linked to lower self-esteem, worse body image or unhealthy eating thoughts, especially in women and younger people. In adults with overweight who were in a treatment programme, links were more often neutral or positive. The authors concluded that adverse effects are possible in some people.

What official guidance says

NIDDK describes safe and successful weight-loss programmes as including daily monitoring of food and activity and weekly monitoring of weight. So weekly weigh-ins are a well-supported baseline, and daily weighing is a reasonable option if it suits you.

Why your weight changes from day to day

A 1 kg jump overnight is almost never 1 kg of fat. To gain a kilogram of body fat you would need to eat several thousand calories more than you burn. Short-term swings come from other things.

Water and glycogen

Your body stores carbohydrate as glycogen in the liver and muscles, and glycogen is stored with water. A paper in the American Journal of Clinical Nutrition (Kreitzman and colleagues, 1992) describes each part of glycogen as being stored with three to four parts water. When you eat fewer carbohydrates for a few days, you use up some glycogen and lose that water too. This is why the first week of a new diet (especially a low-carb one) can show a big drop, and why a carb-heavy meal can put some of it back overnight. Neither change is fat.

Salt

A salty restaurant meal or takeaway can make your body hold on to extra water for a day or two. The scale goes up, then comes back down once your intake returns to normal.

Food and drink still in your gut

Food and drink have weight until they are digested and passed. A large dinner, a late meal or constipation can all add weight that has nothing to do with body fat.

Weekends

A study in Obesity Facts (Orsama and colleagues, 2014) analysed more than 4,600 daily weigh-ins from 80 adults. Weight tended to be highest on Sunday and Monday and to fall during the week. This pattern was strongest in people who lost or maintained weight over time. The authors suggested that small weekend rises should be seen as normal rather than as a sign of weight gain.

Other factors

Hard training (which can cause temporary water retention in muscles), some medicines, illness and, for many women, the menstrual cycle can also move the scale for a few days.

Use a weekly average, not a single reading

Because daily numbers are noisy, the most useful figure is the average over a week. Here is an example from someone who weighs every morning:

	Mon	Tue	Wed	Thu	Fri	Sat	Sun	Average
Week 1	82.4	82.0	81.9	82.2	81.8	81.6	82.3	82.0 kg
Week 2	82.5	81.8	81.6	81.5	81.7	81.2	81.8	81.7 kg

The Monday of week 2 (82.5 kg) is the highest number in the table, but the weekly average fell by 0.3 kg. Looking only at that one day, you might think your plan had stopped working. Looking at the averages, you can see it is on track.

Some practical rules:

Compare this week’s average with last week’s, not today with yesterday.
Look at the trend over three to four weeks before you change anything. If it has been flat for that long, read our guide to the weight loss plateau.
If you weigh only once a week, weigh on the same day each week and remember that one reading can still be off by a kilogram or so.
Check whether your rate of loss is realistic with our guide on how fast you can lose weight safely.

How to weigh yourself consistently

Most of the noise you can control comes from changing conditions. Keep them the same:

Same time of day. First thing in the morning works for most people: after using the toilet, before eating or drinking.
Same clothing. Ideally none, or the same light clothes each time.
Same scale, same spot. Put it on a hard, flat floor and do not move it around. Different scales can give different readings.
Write it down straight away. Log the number without judging it. One reading is a data point, not a verdict.
Note anything unusual. A late salty dinner, a hard workout, poor sleep or your period can explain a jump later.

Weighing in PixNutri

In PixNutri you can log your weight and see it over time next to what you eat. Regular check-ins help you look back at how things are going over weeks rather than days. If you connect Apple Health or Health Connect, PixNutri can read your latest weight from it, so a reading from a connected smart scale shows up in the app.

Your weight also feeds your targets. When you use our calorie calculator or the app, the calorie goal is based on your current weight, so it is worth updating after you have lost a few kilos. For a quick check of where you stand, the BMI calculator gives a rough starting point, though BMI does not tell you about body composition.

When weighing yourself may not suit you

Frequent weighing is not right for everyone. The review in Current Obesity Reports found links between self-weighing and negative outcomes in some groups, particularly women and younger people.

It may be better to weigh less often, or not at all, if:

you have, or have had, an eating disorder or disordered eating
the number on the scale strongly affects your mood or self-worth
you find yourself skipping meals, over-exercising or “making up” for a higher reading
you feel the urge to weigh yourself many times a day

In that case, other signs of progress can work better: how your clothes fit, your energy, your fitness, a waist measurement taken occasionally, or simply regular healthy habits.

The NHS advises speaking to a GP or healthcare professional before trying to lose weight if you have, or have had, an eating disorder. If you are worried about your relationship with food, the NHS recommends seeing a GP as soon as you can. In the UK the charity Beat offers support; elsewhere, ask your doctor about local eating disorder services.

Also talk to a doctor before starting a weight-loss plan if you are pregnant or breastfeeding, under 18, or have a medical condition that affects your weight or diet. A sudden unexplained change in weight is also worth checking with a professional.

FAQ

Is it bad to weigh yourself every day?

Not for most adults trying to lose weight. In the trials above, daily weighing was linked to more weight loss and was perceived positively. It is a problem only if the numbers cause distress or unhealthy behaviour; then weigh less often or stop.

What is the best time to weigh yourself?

In the morning after using the toilet, before eating or drinking, in the same clothing. The point is not that morning weight is “true” but that it is consistent.

Why do I weigh more in the evening?

Food and drink from the day are still in your body, along with the water that comes with them. That is why an evening reading is usually higher than a morning one, and why mixing the two makes your log harder to read.

How much can weight fluctuate in a day?

It varies from person to person. Day-to-day swings from water, salt, glycogen and gut contents can easily be larger than the fat you lose in a week, especially after salty or carb-heavy meals. That is why the weekly average is more useful than any one reading.

Should I weigh myself once a week instead?

Weekly weighing is what NIDDK describes for weight-loss programmes, and it works well if daily weighing feels like too much. Weigh on the same day and at the same time each week, and look at several weeks together.

How Often Should You Weigh Yourself? Daily vs Weekly