Q. Doctor, everyone says they’re dieting with Subway sandwiches. How exactly does it work, and why does it help with weight loss?

The popularity of the Subway diet stems from the consumer's control over ingredients. Dieters typically choose Wheat or Honey Oat bread, exclude pickles, and stick to salt, pepper, and olive oil. Medically, this is a clever strategy to manage 'blood sugar variability.' By avoiding refined carbohydrates and sugary sauces, you prevent insulin spikes, allowing the body to burn energy actively instead of storing it as fat. In Traditional Korean Medicine (TKM), this is understood as preventing the formation of Phlegm-fluid (痰飮), which are metabolic residues. In a state of Spleen Deficiency (脾虛), these residues accumulate throughout the body, leading to weight gain and lethargy. Even in clinical practice, I’ve noticed that eating processed, high-sugar sandwiches results in immediate bloating and heaviness. This dietary approach significantly reduces the burden on the Spleen. Dietary fiber from vegetables helps expel waste, while unprocessed proteins support the circulation of Qi and Blood (氣血). Properly managing sauces also helps prevent Water Toxicity (水毒), which causes unnecessary fluid retention. While hollowing out the bread to reduce carbs is helpful, the most important factor for preventing the yo-yo effect is providing 'clean fuel' that doesn't disrupt your metabolic system.