Does Herbal Medicine Make You Gain Weight? The Misconception and the Truth
The fundamental aim of herbal medicine in Korean Traditional Medicine (KTM), the traditional healing system of Korea also known as Hanbang (한방), is to correct the body’s imbalance and bring it to its healthiest, most balanced state. That correction runs in both directions: a person who is underweight may gain weight as their health returns, while a person carrying excess may shed unnecessary waste and lose it. And yet a persistent misconception follows the medicine around — that taking herbs makes you fat.
In Summary
- Herbal decoctions are water extracts: a single packet (about 100–120 ml) carries only 10–30 kcal — far less than an ordinary drink. The calories alone cannot meaningfully raise your weight.
- Weight that rises during herbal treatment usually reflects one of four things: improved digestion and a bigger appetite; eating more out of a “reward” mindset; the body restoring itself toward a normal weight; or, rarely, a prescription that does not suit you.
- An ill-fitting prescription can destabilize metabolism and bring fatigue, edema, or abnormal hunger — which is why diagnosis and prescribing belong with a KTM physician.
- If you notice worrying weight change, edema, or fatigue, do not stop the medicine on your own — consult the prescriber promptly so the cause can be found and the formula adjusted.
- The short version: you do not get fat from herbal medicine. You get fat from food.
The Misconception: “Herbal Medicine Is High in Calories”
The most common version of the myth is that the medicine itself carries enough calories to put on weight. It does not. Most decoctions are simply herbs extracted in water, and one packet — around 100 to 120 millilitres — contains only about 10 to 30 kilocalories. That is far below what you would get from an everyday beverage. Weight does not meaningfully increase on the strength of those calories.
The Truth: Why the Scale Actually Moves
So why does weight sometimes climb during a course of herbal medicine? The cause lies not in the herbs but in the changes happening in the body — and most of them are positive.
1. Better digestion, bigger appetite. Tonic formulas aimed at restoring energy often focus on lifting the function of a sluggish spleen-and-stomach (비위) — the digestive system. As gastric motility picks up and nutrient absorption improves, appetite naturally grows. The herb has not fattened you; you are simply eating more than before because your digestion works better.
2. The reward mindset. “If I’m taking a tonic, I should eat properly to match” — and so people reach more often for rich restorative dishes, or simply enlarge their meals. The intention is to help the medicine work, but the result can be calories in exceeding calories out, and the weight follows.
3. Recovery toward a healthy state. For someone whose weight had fallen below the normal range through chronic fatigue or illness, regaining energy prompts the body to start actively storing nutrients again as it climbs back toward health. This is not a problem; it is a positive sign of a return from an abnormal state to a normal weight.
4. A prescription that does not fit. Rarely, taking a formula that does not match your constitution or condition can raise weight. When a prescription is wrong for the body, balance breaks down, metabolism becomes unstable, and fatigue, edema, or an abnormal surge in appetite can appear. In such cases, stopping that formula and switching to the correct one usually brings the weight back. This is exactly why an accurate diagnosis and prescription from a KTM physician matters.
Managing Weight While Taking Herbal Medicine
Talk to the prescriber first. If you are worried about a change in weight, or notice edema or unusual fatigue, do not stop taking the medicine on your own — consult the KTM physician who prescribed it, promptly. Identifying the cause and, if needed, adjusting the prescription comes first.
Fill the new appetite with good food. An increased appetite is best met with healthy choices: fresh vegetables and quality protein rather than processed or high-fat foods, so the extra intake stays nutritionally balanced.
Keep moving, gently. Once your energy has recovered, pair the treatment with steady, light activity — a walk, some stretching. It raises energy expenditure and helps with weight, and it also aids the absorption and circulation of the medicine itself, improving its effect.
In Summary
Weight gain during a course of herbal medicine is, in most cases, not a problem with the medicine at all: it is either a positive signal that bodily function is normalizing, or the result of a change in eating habits — and occasionally a sign the formula needs adjusting. The calories in a decoction are trivial. So if the scale moves, look at the appetite, the plate, and the fit of the prescription rather than blaming the herbs — and take any concerns to your prescriber rather than stopping on your own. You do not get fat from herbal medicine. You get fat from food.
Related reading: Stress and False Hunger · The Spleen and Stomach in Korean Medicine
This article reflects the clinical observations and teaching practice of Professor Seungho Baek, Professor of Korean Medicine at Dongguk University College of Korean Medicine, specializing in Pathology and Oncology.
