What exactly is a 'cheating day,' and why does it often seem to ruin my dieting progress?

I truly understand the desperate urge to indulge after strictly dieting; I’ve experienced that 'one day won't hurt' mindset myself. Conceptually, a 'cheating day' is meant to 'trick' the brain so it doesn't lower the metabolic rate out of a perceived starvation state. The problem is that this often becomes toxic to the system. When you suddenly flood your body with high carbohydrates after a period of restriction, insulin is released explosively, flipping the 'fat storage switch.' From the perspective of Traditional Korean Medicine (TKM), this triggers a vicious cycle of Spleen Deficiency (脾虛) and Phlegm-fluid (痰飮). When the Spleen’s transformative function is weak, sudden overconsumption causes the body to produce Phlegm-fluid—a sticky, pathological waste—rather than healthy energy. This accumulation obstructs the circulation of Qi and Blood (氣血), eventually changing your constitution into one that resists weight loss. If cheating escalates into bingeing, it can even lead to Blood Stasis (瘀血), causing the body to feel heavy and swollen. Successful dieting is not a war with your body, but a negotiation. The key is to reward yourself within your digestive capacity. We should first examine your specific constitution and focus on clearing out this accumulated Phlegm-fluid together.