Cet article résume les informations les plus importantes sur : Sodium et rétention d'eau : Pourquoi vous êtes parfois plus lourd.
Why the Scale Changes Day to Day
Body weight is not a fixed number — it fluctuates by 1–4 kg (2–8 lbs) throughout any given day and from day to day, driven primarily by water. Understanding this prevents the most common source of diet discouragement: seeing the scale go up after a good week of eating.
The Major Causes of Day-to-Day Weight Fluctuation
| Factor | Weight change | Duration |
|---|---|---|
| High sodium meal | +0.5–2 kg | 24–72 hours |
| High carbohydrate meal | +0.5–1.5 kg | 24–48 hours |
| Alcohol | +0.5–1 kg (initial dehydration, then rebound) | 24–72 hours |
| Menstrual cycle (women) | +0.5–3 kg pre-period | 3–7 days |
| Dehydration | -0.5–2 kg | Hours |
| Food volume in GI tract | +0.5–1.5 kg | Until elimination |
| Exercise (inflammation) | +0.3–1 kg | 24–72 hours |
How Sodium Causes Water Retention
Sodium is the primary electrolyte regulating extracellular fluid volume. For every gram of sodium consumed, the body retains approximately 100–200 ml of water to maintain osmotic balance (a sodium concentration of ~140 mmol/L in blood). A meal with 3,000 mg of sodium (common in restaurant food) can trigger retention of 300–600 ml of water — 0.3–0.6 kg on the scale — within hours.
This retained water is not fat. It resolves within 24–72 hours as the kidneys excrete the excess sodium and water returns to baseline.
Carbohydrates and Water Weight
Every gram of glycogen (stored carbohydrate) is stored with 3–4 grams of water. After a high-carbohydrate meal, glycogen stores replenish and water is retained alongside them. This is why low-carb diets produce rapid initial weight loss — glycogen depletion releases 1–3 kg of water quickly. This water loss is not fat loss, and it returns when carbohydrate intake is restored.