# Why the scales go up and down Your weight changes from day to day, even when body fat barely does. Much of this is water. ## Carbohydrates bind water The body stores carbohydrates as glycogen, together with three to four times as much water. That is why weight often drops quickly at the start of a diet and can rise quickly after a carbohydrate-rich meal.[^1] ## What disappears quickly at the start An old but direct measurement shows the size of this: in 6 people on 800 kcal a day, 61% of the weight lost on a ketogenic diet was water, against 37% on a mixed diet.[^5] So quick results in the first week say little about body fat. ## And salt? Salty food, more on the scale the next day: you hear this a lot, but the picture is less clear. In 32 healthy men under lab conditions, more salt raised neither body water nor weight.[^6] In a small study of 9 men, on the other hand, fluid outside the cells rose by about 2 litres when they went from little to normal salt.[^7] So it depends on where you start. There is no reliable figure in kilos. ## What is in the gut Gut content counts too. Healthy adults in a British study passed a median of 106 g of stool a day, and the trip through the gut took about 60 hours.[^8] More fibre raises stool weight, especially from cereals and vegetables.[^9] So a high-fibre week can briefly show more without any added fat. ## Your cycle plays a part In a study of 62 healthy women and 765 cycles, the feeling of fluid retention was strongest on the first day of the period.[^2] These were self-reports, not readings from scales. ## The week has a rhythm too An analysis of 4,657 measurements from 80 adults found higher values on Sunday and Monday than later in the week. The authors consider this normal.[^3] ## Medicines and the pill Some medicines change weight. A review of 257 studies found an average of 1.5 to 2.6 kg more with single drugs for depression, psychosis, seizures or diabetes.[^10] Blood pressure drugs from the calcium channel blocker group led to swollen ankles in 10.7%, against 3.2% in the comparison group.[^11] Don't stop anything on your own, talk to your doctor. For the pill, a Cochrane review found no large effect on weight, but the data are too thin to rule out any effect.[^12] ## How much to drink DGE gives about 1,410 ml a day from drinks for adults aged 25 to under 51. Needs are higher with heat, a lot of activity or fever.[^4] ## How often to weigh yourself? Weighing alone does little: in a review of trials, daily was not better than weekly, and it worked better with the support of a programme.[^13] In adults who want to lose weight, regular weighing was not linked to more depression or anxiety.[^14] That does not hold for everyone, though. In 69 young women, daily weighing brought more mood swings and less body satisfaction within two weeks.[^15] In teenage girls, frequent weighing was linked to later binge eating.[^16] If the number stresses you, weigh less often or not at all. If you have an eating disorder or are afraid of one, read [When to get medical advice](https://kostenlos-abnehmen.de/en/wissen/aerztlicher-rat). ## How to read the values Compare means over weeks, not single days. Weighing is optional in the app, and you do not have to do it every day. ## Sources [^1]: [Kreitzman SN et al.: Glycogen storage: illusions of easy weight loss, excessive weight regain, and distortions in estimates of body composition. Am J Clin Nutr, 1992](https://pubmed.ncbi.nlm.nih.gov/1615908/) [^2]: [White CP et al.: Fluid Retention over the Menstrual Cycle: 1-Year Data from the Prospective Ovulation Cohort. Obstet Gynecol Int, 2011](https://pubmed.ncbi.nlm.nih.gov/21845193/) [^3]: [Orsama AL et al.: Weight rhythms: weight increases during weekends and decreases during weekdays. Obes Facts, 2014](https://pubmed.ncbi.nlm.nih.gov/24504358/) [^4]: [DGE: Reference values for water (German)](https://www.dge.de/wissenschaft/referenzwerte/wasser/) [^5]: [Yang MU, Van Itallie TB: Composition of weight lost during short-term weight reduction. J Clin Invest, 1976](https://pubmed.ncbi.nlm.nih.gov/956398/) [^6]: [Heer M et al.: High dietary sodium chloride consumption may not induce body fluid retention in humans. Am J Physiol Renal Physiol, 2000](https://pubmed.ncbi.nlm.nih.gov/10751219/) [^7]: [Heer M et al.: Increasing sodium intake from a previous low or high intake affects water, electrolyte and acid-base balance differently. Br J Nutr, 2009](https://pubmed.ncbi.nlm.nih.gov/19173770/) [^8]: [Cummings JH et al.: Fecal weight, colon cancer risk, and dietary intake of nonstarch polysaccharides. Gastroenterology, 1992](https://pubmed.ncbi.nlm.nih.gov/1333426/) [^9]: [de Vries J et al.: Effects of Cereal, Fruit and Vegetable Fibers on Human Fecal Weight and Transit Time. Nutrients, 2016](https://pubmed.ncbi.nlm.nih.gov/26950143/) [^10]: [Domecq JP et al.: Drugs commonly associated with weight change. J Clin Endocrinol Metab, 2015](https://pubmed.ncbi.nlm.nih.gov/25590213/) [^11]: [Makani H et al.: Peripheral edema associated with calcium channel blockers. J Hypertens, 2011](https://pubmed.ncbi.nlm.nih.gov/21558959/) [^12]: [Gallo MF et al.: Combination contraceptives: effects on weight. Cochrane Database Syst Rev, 2014](https://pubmed.ncbi.nlm.nih.gov/24477630/) [^13]: [Madigan CD et al.: Is self-weighing an effective tool for weight loss. Int J Behav Nutr Phys Act, 2015](https://pubmed.ncbi.nlm.nih.gov/26293454/) [^14]: [Zheng Y et al.: Self-weighing in weight management: a systematic literature review. Obesity, 2015](https://pubmed.ncbi.nlm.nih.gov/25521523/) [^15]: [Pacanowski CR et al.: Daily self-weighing compared with an active control causes greater negative affective lability in emerging adult women. Appl Psychol Health Well Being, 2023](https://pubmed.ncbi.nlm.nih.gov/37339756/) [^16]: [Neumark-Sztainer D et al.: Self-weighing in adolescents: helpful or harmful? J Adolesc Health, 2006](https://pubmed.ncbi.nlm.nih.gov/17116510/) --- Last updated: November 2026. This is general information and not medical advice. Original article: https://kostenlos-abnehmen.de/en/wissen/wasser-und-gewicht