Gained weight in a day or two? It may be water: common causes and everyday habits
Some of the short-term change you see on the scales can come from water your body is holding. Sometimes there is mild swelling in the ankles, feet or legs too.
This article sums up common everyday contributors, based on public health sources. If swelling does not go away, affects only one side or comes on suddenly, see a doctor.
Common everyday contributors
- Standing or sitting in the same position for a long time – a common cause of swollen legs
- Eating too much salty food
- Hot weather, especially after standing or walking a lot
- Before a period, some people notice bloating or feel puffy
- Pregnancy and some medicines, such as the contraceptive pill, hormone therapy, steroids or some blood pressure medicines
Carbohydrate and water in muscle
- The body stores some carbohydrate in muscle as glycogen
- Research in people found that each gram of glycogen is stored with at least about 3 g of water
- So the scales can move with your meals and exercise from day to day
- Look at your weight trend over time rather than any single day's reading
Everyday habits
- Cut down on salt – WHO recommends adults have less than 5 g a day (under 2,000 mg sodium)
- Choose fresh or minimally processed food, limit sauces and instant products, and flavour with herbs and spices
- Eat fresh fruit and vegetables – WHO notes this is a way to increase potassium intake from food
- If you sit or stand for long periods, move regularly, raise your legs when resting and avoid tight clothes, socks or shoes
- Drink enough – the NHS suggests about 6 to 8 glasses of fluid a day as a guide
When to see a doctor
- Both legs are swollen and not better after a few days, or the swelling is getting worse
- Only one leg is swollen for no clear reason, or the swelling is large, painful, red, hot or sudden
- You have a heart, kidney or liver condition, or diabetes, and notice swelling
- Swelling with breathlessness, chest tightness or chest pain needs emergency care straight away
Read next: What does water do in your body? Plus natural ways to flavour it ›
Read next: How much water should you drink? About 2 litres a day ›
Read next: Why weight creeps up with age, and 6 ways to manage it ›
This article is general health information, not a diagnosis, and results vary from person to person. If you have a medical condition, are pregnant or take medication, talk to your doctor first before changing your diet, especially if you have been told to limit fluids or potassium. Ask us on LINE.
Image and reference from official material in the MyHerbalife media library: Staying properly hydrated in summer (illustration) (added to the library: 20 Sep 2025)
Reference: NHS: Swollen ankles, feet and legs (oedema) (viewed 14 Oct 2026) ↗ (opens in a new tab)
Reference: nidirect (Northern Ireland government): Oedema (viewed 14 Oct 2026) ↗ (opens in a new tab)
Reference: MedlinePlus (US National Library of Medicine): Swelling (viewed 14 Oct 2026) ↗ (opens in a new tab)
Reference: World Health Organization (WHO): Salt reduction (viewed 14 Oct 2026) ↗ (opens in a new tab)
Reference: World Health Organization (WHO): Healthy diet (viewed 14 Oct 2026) ↗ (opens in a new tab)
Reference: NHS: Water, drinks and your health (viewed 14 Oct 2026) ↗ (opens in a new tab)
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Compiled by Well Nutrition Hub from the sources listed at the end of this article. Copyright in the referenced content, images and media belongs to the respective rights holders. You are welcome to share the link to this article.