Salt, Water, and Electrolytes During the Fasting Window: Why Your Head Hurts Not Because of Hunger
Headache, weakness, and “hunger” during the first days of a pause are most often not about food, but about salt and water. When insulin is low — and it is low during a pause and on a low-carbohydrate diet — the kidneys excrete more sodium, and water leaves with it. Replenishing it is simple: 3-5 g of salt per day, 2-2,5 liters of water, some of it salted mineral water, plus potassium and magnesium from food. Below is why this happens, how much is needed, and how to understand exactly what is lacking.
3-5 g
of salt per day
2-2.5 l
of water
1 l
of salty mineral water
3 days
when it is hardest
Why does salt leave during the pause?
Insulin is a hormone that is about more than just blood sugar. One of its functions is to retain sodium in the kidneys. When you eat carbohydrates, insulin is elevated, and sodium and water are retained in the body — hence the swelling after a salty-sweet dinner. When insulin drops — during the pause, and almost constantly on a low-carbohydrate diet — the kidneys begin excreting sodium more actively, and water follows.
This is why the first days of a low-carbohydrate diet or fasting bring a sharp weight loss of 1-2 kg: water is lost, not fat. And why during these same days you may have a headache, feel sleepy, and «feel hungry»: the body lacks sodium and fluid volume. There is nothing dangerous about this for a healthy person if salt is replenished. The problem begins when salt is instead restricted «for health».
That is precisely why, in Anastasia’s method, salt is not an enemy but a mandatory element: 3-5 g per day, and if you cannot get that much from food — at least a liter of salty mineral water. This same sodium deficiency is behind what is called keto flu.
Three electrolytes: how much and where to get them
| Electrolyte | Daily guideline | Where to get it | Signs of deficiency |
|---|---|---|---|
| Sodium (salt) | 3-5 g of salt | salt in food, mineral water with salt, sauerkraut, broth | headache, weakness, dizziness when standing up |
| Potassium | 3-4 g | avocado, spinach, leafy greens, mushrooms, salmon | cramps, muscle weakness, heart palpitations |
| Magnesium | 300-400 mg | nuts, pumpkin and chia seeds, 85% dark chocolate, mineral water | nighttime calf cramps, twitching eyelid, poor sleep |
Water: how much, and why “more” doesn’t mean “better”
The guideline from the method is 2-2,5 liters a day, and up to 3 in summer and during workouts. But there is a catch: if you drink a lot of water without eating salt, the sodium in your blood becomes diluted, and you feel worse — weakness, nausea, brain fog. Marathon runners know this condition, but you can also end up in it during a fasting break if you try to “drink away hunger” with water.
The rule is simple: water — with salt. A pinch in a glass in the morning, salted mineral water during the day, salty food during the eating window. Then the water stays in your body instead of passing straight through. If you need to use the bathroom immediately after a glass of water, but your thirst does not go away, you are lacking sodium, not water.
Coffee and tea count toward your fluid intake — caffeine’s diuretic effect is mild and almost disappears with regular use. What else to drink during a fasting break, and what already counts as food, is explained in the article what you can drink during a fasting break.
How to replenish electrolytes throughout the day
Morning, immediately after waking up
A glass of water with a pinch of salt — a quarter of a teaspoon. This relieves morning sluggishness and ‘hunger,’ which is actually thirst.
Pause, before the first meal
Coffee with cream, water, salty mineral water. If you train fasted — salt before the workout, mineral water afterward.
First meal
Salt your food normally, don’t be afraid. A 150 g salad with olive oil, vinegar and Himalayan salt, avocado — that’s potassium and magnesium.
Dinner
At least 30 g of sauerkraut — salt and potassium. A handful of nuts or chia seeds — magnesium. Fatty fish — potassium and magnesium together.
Before bed, if your calves cramp
Magnesium in the evening: mineral water with magnesium or a supplement after consulting a doctor. Night cramps are almost always magnesium.
Salt — 3-5 g per day, approximately one teaspoon. If you can't consume that much salt, drink salty mineral water, at least one liter per day.
How to understand what’s missing: salt, potassium, or magnesium?
Three electrolytes cause similar weakness, but each has its own “signature.” Sodium: headache, dizziness when standing up, daytime sleepiness, “hunger” an hour after a substantial meal. It goes away with salt water in 15-20 minutes—that’s the test.
Potassium: cramps, palpitations, muscles feel “flabby,” especially in the legs. Potassium from supplements should be taken cautiously and only as prescribed by a doctor, while it’s difficult to overdo it from food: half an avocado, 150 g of spinach, and 100 g of salmon provide more than a gram.
Magnesium: nighttime calf cramps, a twitching eyelid, anxiety, poor sleep. A low-carb diet usually provides enough magnesium if you eat nuts and seeds every day—in this method, that means 2-3 tablespoons of flax and chia seeds plus a handful of nuts. If you can’t sleep at night and feel drawn to the refrigerator, magnesium is the second thing to check after dinner.
Normal during the pause
- A wave of mild hunger that goes away with water and salt
- Slight weakness during the first 3 days
- Loss of 1-2 kg of water during the first week
- Stomach rumbling between meals
Signal to add salt and water
- Headache every morning
- Dizziness when standing up from a chair
- Heart palpitations and trembling during the pause
- Cramps at night, "cottony" legs
Common mistakes with salt and water
- Removing salt “so as not to swell” — during a break, this works the opposite way
- Drinking 3-4 liters of water without salt to “stifle hunger”
- Expecting the headache of the first few days to go away on its own instead of having a pinch of salt
- Drinking sugary sports drinks for the sake of electrolytes
- Taking potassium tablets without tests and a doctor
Frequently Asked Questions
Which salt is best?
The method recommends Himalayan salt: it contains slightly more potassium, calcium, and magnesium. But the main purpose of salt is to provide sodium, and any salt does that. Iodized salt is a good choice if you don’t eat fish and seafood.
Is it harmful to eat 5 г of salt a day?
For a healthy person on a low-carb diet — no: the kidneys excrete some sodium on their own because insulin is low. If you have hypertension or kidney or heart disease, discuss it with your doctor; there are no general guidelines here.
Are electrolyte powders necessary?
They’re convenient, but not essential. Salt, mineral water, avocado, greens, nuts, and sauerkraut provide everything you need. If you choose a powder, make sure it contains no sugar or maltodextrin.
How much water is already too much?
If you drink more than 3-3,5 L, your urine is completely colorless, and you feel worse rather than better, that’s too much. Add salt and cut out a liter.
- Fasting Schedules
- How Fasting Feels
- Meals Around the Window