Why does my weight fluctuate so much?
If your weight jumps a kilo overnight, you didn’t gain a kilo of fat. Here’s what did change.
Short answer
Day-to-day swings of 1–2 kg (2–4 lb) are normal and mostly water: salt, carbohydrates (each gram of stored glycogen holds roughly 3 grams of water), food still in your gut, hard training, poor sleep and hormones. Use a weekly average and photos instead of single weigh-ins.
The usual causes
| Cause | Effect | How long |
|---|---|---|
| Salty meal | Water retention | 1–3 days |
| More carbs than usual | Glycogen + water stored | 1–3 days |
| Food and drink not yet digested | Weight in the gut | Up to 1–2 days |
| Hard or new training | Muscle repair, inflammation, water | 2–5 days |
| Menstrual cycle | Water retention before a period | Several days |
| Poor sleep, stress | Hormonal water retention | Varies |
How to track through it
- Weigh at the same time, same conditions, ideally each morning.
- Look at the 7-day average, not today’s number.
- Use waist and photos, which barely react to water, as your tie-breakers.
FAQ
Frequently asked questions
How much weight fluctuation is normal in a day?
1–2 kg (2–4 lb) is common, sometimes more after a salty or high-carb day.
Should I weigh myself every day?
Daily weighing plus a weekly average gives the clearest trend. If it affects your mood, weigh weekly.