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Swelling, Circulation, Weight, and Water Metabolism

Reviewed by: 자임당
Swelling, Circulation, Weight, and Water Metabolism

On the way home from work, your shoes feel tight, and the next morning, the scale shows a number more than 1 kg higher. You don't recall eating an unusual amount the day before. Conversely, after practically starving for a few days, the number drops sharply, only to return to its original position two days after resuming normal meals.

If you interpret all these numbers as body fat, your judgment will consistently be off. A scale measures the entire body. Inside it are not just fat and muscle, but also undigested food in the stomach, unexcreted feces, and, most importantly, water. This is where swelling, body weight, and water metabolism intertwine.

Grains in a glass jar and a bottle of water
Grains in a glass jar and a bottle of water

A 1 kg Fluctuation in a Day Is Not Fat

Carbohydrates are stored in the liver and muscles in the form of glycogen. However, glycogen is not stored alone. It brings water with it.

A study on the relationship between muscle water and glycogen recovery published in the 『European Journal of Applied Physiology』 (European Journal of Applied Physiology) in 2015 tracked the recovery process of 9 trained adults after prolonged exercise in a hot environment. Under conditions of restricted fluid intake, a 1:3 ratio was confirmed, where 3 g of water was stored in the muscles along with 1 g of glycogen. Under conditions of sufficient fluid intake, the ratio increased to 1:17, meaning there is also water stored independently of glycogen.

Glycogen stored in the liver and muscles is measured in hundreds of grams. Calculations show that body weight can fluctuate by 1-2 kg simply by the storage being emptied and refilled. Sodium works in the same way. The number on the scale rises the day after consuming salty soup because the salt retains water.

Body fat does not fluctuate like this. It changes slowly over several weeks, depending on energy balance. It is closer to the truth to consider a 1 kg fluctuation within a day as coming from water.

Why the Scale Drops Significantly in the First Week of Low-Carb Diets

Understanding this structure allows for a different interpretation of the rapid weight loss in the initial stages of dieting.

A study on the composition of weight lost during short-term weight reduction published in the 『Journal of Clinical Investigation』 (Journal of Clinical Investigation) in 1976 compared isocaloric low-carbohydrate ketogenic diets and mixed diets for 10 days each, analyzing what the reduced weight consisted of. The low-carbohydrate group lost approximately 467 g per day, with a composition of 61.2% water, 35.0% fat, and 3.8% protein. The mixed diet group lost weight more slowly, at approximately 278 g per day, but its composition was 37.1% water, 59.5% fat, and 3.4% protein.

This means that the group with faster weight loss accounted for more than half of their reduction as water. When carbohydrates are consumed again, glycogen and water also return. A 1-2 kg increase in weight a few days after stopping a diet is not due to gaining that much fat, but rather the refilling of previously emptied stores. It is closer to an expected outcome than evidence of failure.

Empty chair by the window and sneakers on the floor
Empty chair by the window and sneakers on the floor

Calf Muscles Pump Venous Blood Up the Legs

When discussing water metabolism, it's easy to only think of the kidneys, but whether water accumulates in tissues is also determined by lower limb circulation.

Arteries are directly pushed by the heart. Veins are different. They must return blood from the toes to the heart against gravity, but their pressure is low. Therefore, two mechanisms are used: venous valves that prevent backflow, and the calf muscles. Each time the muscles contract, the deep veins between them are compressed, pushing blood upwards, and during relaxation, the valves prevent it from flowing back. This is why the calf is called the second heart. Lymphatic vessels, which collect interstitial fluid and return it to the veins, also largely depend on the slow contraction of the vessels themselves and the movement of surrounding muscles.

The problem is that this pump only operates when muscle contraction and relaxation are repeated. It stops when you sit for a long time. The situation is no different even if you stand almost without changing your posture, such as at a checkout counter or in front of a cooking station. This is why people who sit all day and people who stand all day report the same symptoms in the evening. The phenomenon of swollen feet after a long flight is the clearest example illustrating this structure.

What Is Evidence-Based and What Is Merely Appealing to Numbers

Commonly recommended methods have varying levels of evidence.

Compression is the most well-documented. The Cochrane Review 「Compression stockings for preventing deep vein thrombosis in airline passengers」 (revised 2021) examined 12 randomized trials involving 2,918 participants and meta-analyzed 9 of them, totaling 2,637 participants. Leg swelling was reduced in 6 trials with a mean difference of −4.72 (95% confidence interval −4.91 to −4.52), but due to limitations in swelling measurement methods, the level of evidence was rated as low. In contrast, asymptomatic deep vein thrombosis was found in 50 out of 2,637 participants, with 3 wearing stockings and 47 not wearing them (odds ratio 0.10). For this outcome, the level of evidence is high. This means that even with the same compression, the weight of the evidence changes depending on the target.

Exercise is different. The Cochrane Review 「Physical exercise for non-ulcerated chronic venous insufficiency」 (2023) gathered 5 randomized trials with 146 participants, but the difference in calf pump ejection fraction at 6 months was unclear, and all symptom and quality of life indicators had a very low level of evidence. Leg elevation is simple in principle, but clinical data is sparse.

The diuretic effect of coffee or tea temporarily expels water. The number on the scale might drop the next day, but the underlying structures of valves, muscle pumps, and lymphatic pathways remain unchanged. Arbitrarily obtaining and taking diuretics cannot be recommended more clearly. A paper titled 「Diuretic Administration in Patients with Renal Disease」 published in the 『대한내과학회지』 (The Korean Journal of Medicine) summarizes that loop diuretics can cause hyponatremia, hypokalemia, hypomagnesemia, and metabolic alkalosis, while thiazide diuretics can additionally cause fluid volume depletion, impaired glucose tolerance, and hyperuricemia. Potassium-sparing diuretics, conversely, can worsen hyperkalemia. These are medications used while monitoring electrolytes and kidney function, not something to start on your own simply because you appear swollen.

Folded compression stockings and a glass of water on linen
Folded compression stockings and a glass of water on linen

Korean Medicine Distinguishes Between *Isu* and *Bogi*

Korean medicine also has a framework corresponding to water metabolism. The nature of water is called *susup* (水濕, water-dampness), and problems with its circulation are addressed in the language of *gihyeolsunhwan* (氣血循環, qi and blood circulation). Here, there is a divergence: it does not group the same phenomenon as either water accumulating due to excess, or water accumulating due to insufficient power to push it up.

The 「비만 한의표준임상진료지침」 (Korean Standard Clinical Practice Guidelines for Obesity) (2024), developed by the Korean Society of Korean Medicine for Obesity and listed on the National Korean Medicine Clinical Information Portal, also divides *byeonjeung* (pattern identification) into two axes. The *siljeung* (實證, excess pattern) side includes *seup* (濕, dampness), *dam* (痰, phlegm), *eohyeol* (瘀血, blood stasis), and heat accumulation in the spleen and stomach, while the *heojeung* (虛證, deficiency pattern) side includes *giheo* (氣虛, qi deficiency), *biheo* (脾虛, spleen deficiency), and *yangheo* (陽虛, yang deficiency).

*Isu* (利水, promoting diuresis) aims to expel accumulated water, while *bogi* (補氣, supplementing qi) addresses the power that moves water. In Korean medicine, if water is continuously removed in a state judged as *giheo* (qi deficiency), it is believed that the *gi* (vital energy) will further decline. Therefore, Korean medicine does not equate the approach to swelling with "simply removing water like a diuretic."

Which approach is appropriate is determined through a clinical examination, including interviews and pulse diagnosis.

The sequence is clear. After screening for warning signs and confirming the absence of underlying diseases, lifestyle management and prescriptions follow. Jaimdang's Gongmicha is a food (tea) containing ingredients like corn silk and is not intended for the prevention or treatment of diseases. Gongbihwan, which is considered when weight management and a tendency to swell are intertwined, is different in nature. It is a medicine whose consumption is determined through a Korean medicine doctor's examination and prescription. Its preparation involves a process where standardized herbal ingredients are quantitatively analyzed for marker compounds using HPLC at an off-site herbal dispensary in Paju, Gyeonggi Province, with quality control checks for each batch. The criteria for distinguishing the causes of morning swelling are separately detailed in [Swelling and Edema: What's the Difference?](/en/journal/swelling-water-metabolism-basics).

Dried medicinal herbs like Astragalus root on a wooden tray
Dried medicinal herbs like Astragalus root on a wooden tray

Four Things to Check First When Your Weight Suddenly Increases

  • Recall yesterday's carbohydrates and soup — The day after increasing carbohydrate intake again or consuming salty soup, glycogen and sodium retain water. See if it returns to normal within 2-3 days.
  • Distinguish between returning within two days and continuously rising for several days — A continuous increase in one direction for several days, rather than fluctuation, reflects fluid retention and warrants medical consultation.
  • Observe the time spent sitting or standing and your leg circumference in the evening — If you spent a long time without changing posture, your muscle pump has rested. Also check if only one leg has become thicker.
  • Note anything new started for diuretic purposes — If you have arbitrarily started diuretics, supplements, or high-caffeine beverages, record the timing and dosage and inform your doctor during consultation.

References

*This article is intended to provide information on swelling, body weight, and circulation, and does not guarantee the diagnosis or treatment efficacy of specific diseases. Gongmicha is a food product and is not intended for the prevention or treatment of diseases. Gongbihwan is a prescription medicine whose consumption is determined through a Korean medicine doctor's examination and prescription, and individual responses may vary. Diuretics should not be taken arbitrarily without medical consultation. If only one leg swells, you experience shortness of breath, or your weight continuously increases over several days, seek medical attention without delay.*

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