Why the scales have stopped going down and how often to weigh yourself

You eat as your plan says, and today the scales show more than yesterday. Or they show the same number for two weeks. Both are common, and both have an explanation.

Why the scales go up and down

Your weight changes within the week without any change in your body fat.

• The weekend. In a study of 80 adults with more than 4,600 weigh-ins, weight was highest on Sunday and Monday. It rose from Saturday and fell from Tuesday. In a European study of 1,421 people, the difference within the week was about 0.35% of body weight, or about 0.3 kg for someone weighing 80.
• Water. Carbohydrates are stored in the muscles as glycogen, together with at least 3 g of water for every gram. After a day with a lot of carbohydrate, the scales can go up because of the water.
• Changes over two weeks. In 46 adults who were not dieting, 84% of the change in weight over two weeks was fat-free mass, mostly water.
• The menstrual cycle. In 62 women, the fluid retention they felt was greatest on the first day of their period and increased around ovulation. This is based on what the women reported, not on measured weight.
• Salt. The studies do not give a simple answer. In 32 men, a lot of salt did not increase body water. In 9 men, going from low to normal salt increased body fluids by about 2 litres, while even more salt did not. So salt may affect the scales, but not in a simple way.

A kilo of fat needs about 7,700 kcal more than you burn. If the scales go up a kilo in one day, it is not fat. That is why the app shows the 7-day average as its main number and never celebrates or warns you because of a single weigh-in.

How often to weigh yourself

A 2015 analysis brought together the trials on self-weighing:

• People told to weigh themselves every week and people told to weigh themselves every day showed no significant difference.
• When weighing was added to a weight-loss programme, participants lost 1.7 kg more on average.
• Weighing on its own, without a programme, showed no benefit.

These findings are of low certainty, because there were few trials. Another review of 17 studies found that regular weighing is linked with greater weight loss and is not linked with depression or anxiety. These were observational studies, so they show a link, not that weighing causes the weight loss.

In the MesogeaFit app you weigh yourself at least once a week, with at least two days between weigh-ins. Weigh yourself under the same conditions each time: in the morning, after using the toilet, before eating, in the same clothes or none. If the number makes you anxious, the app can hide it and show you only the trend.

What a plateau is

There is no official definition. In the app, we call it a plateau when the 7-day average does not change for 3 weeks while your logs show that you are eating as the plan says. This is our own choice, based on what follows.

Why a plateau happens

Most of it comes down to simple arithmetic.

• A smaller body needs less energy, about 24 kcal less a day for every kilo you lose. With 8 kg less, you need about 190 kcal less.
• Appetite goes up. In a study of people with type 2 diabetes taking canagliflozin, a medicine that removes calories through the urine, appetite rose by about 100 kcal a day for every kilo lost, more than energy use fell.
• The US guidelines say that the greatest weight loss usually comes at around 6 months, after which weight levels off. A 2014 mathematical model showed that this plateau is explained mainly by small departures from the plan that add up over time, and less by changes in metabolism.

The plan that got you this far was made for your old weight. At some point, what you eat becomes the maintenance calories for your new weight.

Has your metabolism ‘got stuck’?

Measurements show that the extra fall in metabolism, beyond what you would expect for a smaller body, is small:

• In 171 women who lost 12 kg, resting metabolic rate was 54 kcal a day lower than expected straight afterwards. At one and two years it did not differ from what was expected.
• In 71 adults who lost 14 kg, the difference was 92 kcal while they were still dieting, 38 kcal once their weight had stabilised and almost zero at one year.

The finding that this adaptation is small with ordinary diets is fairly certain. The exception is extreme cases. Fourteen contestants from a television weight-loss competition, who lost 58 kg in 30 weeks with very intense exercise, had a metabolism about 500 kcal lower than expected 6 years later.

The calories you don't see

In an old but well-known study, 10 people who said they could not lose weight on less than 1,200 kcal had a normal metabolism. When what they actually ate was measured, they had recorded 47% less food and 51% more activity on average. They were not lying. It is very hard to judge portions by eye. The study was small, so the size of the gap is of low certainty.

If the scales will not move, a week of weighing your food, especially oil, bread and snacks, can show where the calories missing from your logs are hiding.

What the app does at a plateau

1. It first checks whether your logs are consistent.
2. If they are, it lowers your calories by 5% to 10%, without ever going below the safe floor.
3. If you have reached the floor or have been dieting for more than 12 weeks, it suggests a break of 1 to 2 weeks at maintenance calories before you carry on.

When it is not a plateau

Talk to a doctor, not to the app, if:

• your weight is rising fast with no explanation, by more than 2 kg in one week, or you have swelling in your legs,
• your periods have stopped,
• you have heart or kidney disease.

If weighing upsets you a lot or you have a history of an eating disorder, weighing in the app can be made optional. Also talk to someone you trust or to your doctor.