One-Food Diets: From Bananas to Apples and Eggs

In the clinic, I often hear patients ask, "Doctor, is it true I can lose weight by only eating bananas?" I understand the temptation when these single-food diets trend so heavily on social media. To be honest, I once tried an apple-only diet for a few days years ago, and I still vividly remember how dizzy I felt.

What Exactly is a One-Food Diet?

A one-food diet is exactly what it sounds like: a diet/weight management method that relies almost entirely on one specific food. Usually, it involves eating the designated food for two meals and a small portion of a regular meal for the third, or replacing almost all meals with that single food for a certain period. According to a medical media summary, the core idea is to drastically reduce daily calorie intake by repeatedly eating a single, accessible food like bananas, apples, sweet potatoes, or eggs.

Common variations include the banana diet, apple diet, potato diet, tomato diet, egg diet, and the Emperor (meat) diet. Because they are simple, they are easy to start—but that also means there are many pitfalls to watch out for.

Why Does It Feel Like You're Losing Weight Fast?

The principle is surprisingly simple. For an average adult weighing 60kg, the recommended daily energy intake is about 1800–2100 kcal. A one-food diet creates a low-calorie meal plan where intake drops significantly to around 1000–1200 kcal. In short, the temporary weight loss isn't due to some "mysterious efficacy" of a single food, but rather due to calorie restriction.

Following the same logic, you would see similar results by reducing the portion size of any food. It’s not that the banana worked magic; the number on the scale dropped briefly because you cut your usual intake by nearly half. Confusing this point makes it easy to fall into the misconception that "this specific food causes weight loss."

The Reality Behind Popular One-Food Diet Items

Let's look at the banana diet first. One banana is about 98 kcal, which seems manageable, but the nutritional composition is heavily skewed. While rich in carbohydrates, dietary fiber, and potassium, it lacks essential nutrients like protein, fat, and iron.

The apple diet is similar. Its low calorie count certainly helps reduce total intake, but it results in a diet deficient in fat, protein, and fat-soluble vitamins. The same applies to "mono diets" involving tangerines, watermelons, or mangoes that trend on social media. One source points out that such single-fruit diets have a high probability of a yo-yo effect, even suggesting they should not be continued for more than two weeks.

Vegetable-based diets aren't much better. Cucumbers and tomatoes provide plenty of water and fiber but almost no protein. Potatoes and sweet potatoes are primarily carbohydrates, leaving other nutritional gaps. Protein-focused foods like eggs or tofu are slightly better, but since they lack vitamins and fiber, you still end up with an unbalanced diet.

Observed Side Effects in Practice

Looking only at the scale, it might seem like you've lost 1–2 kg in just a few days. However, hearing the stories of patients in my clinic reveals a different picture. While there may be short-term weight loss, it is often followed by side effects such as nutritional imbalance, muscle loss, hair loss, anemia, constipation or diarrhea, menstrual irregularities, and the yo-yo effect.

I have seen female patients visit because their menstrual cycles were disrupted after prolonged fruit-only diets lacking protein. Others worry about losing more hair than usual. Above all, once they return to regular meals, the yo-yo effect—where they gain back more than they lost—follows almost like a formula. This is why experts do not recommend one-food diets.

The Korean Medicine Perspective

In Korean medicine, a diet consisting of only one type of food for a long period is seen as a habit that breaks the balance of the Spleen and Stomach (비위). The Spleen and Stomach are the pathways through which our bodies accept food and convert it into energy. When the same food is consumed repeatedly, the rhythm of digestion and absorption becomes monotonous, causing vital energy (Qi) to become biased.

For example, if you eat fruits with a "cold nature," like apples or bananas, for every meal, your internal system becomes cold, which can lead to loose stools or cold hands and feet. Conversely, a protein-only diet can dry up body fluids (진액), leading to constipation and dry skin. What started as an attempt to lose weight ends up creating constitutional imbalances such as Qi deficiency, Blood deficiency, and Phlegm-dampness. Therefore, I advise patients to "eat less but eat a variety of foods suited to your constitution" rather than relying on a single item.

Practical Tips for Immediate Application

To see results while avoiding extremes, just remember these points:

• Don't replace a whole meal with just bananas or apples; include protein (eggs, tofu, lean meat) and vegetables.
• If you must try a fruit-only diet, do not exceed two weeks for safety.
• Instead of suddenly dropping your daily total below 1000 kcal, start by reducing processed foods and simple sugars from your current diet. This minimizes side effects.
• If you experience constipation, menstrual irregularities, or dizziness, stop immediately and return to regular meals. Your body's signals are the most accurate.
• Even if you eat the same amount, chewing thoroughly and eating slowly helps you feel full faster and reduces the burden on your Spleen and Stomach.

I often see patients whose physical condition improves significantly after just a month of changing a few small habits.

One-food diets come with a high price for their perceived speed and simplicity. No one wants to experience losing their hair, their period, and their energy along with the weight. At Baekrokdam Clinic, we offer the Baekrok Gambi-jung program, which combines herbal medicine with dietary coaching tailored to each patient's constitution and lifestyle rhythm. If you want to manage your weight healthily without relying on a single food, let's talk in the clinic.