The yo-yo effect is not simply weight regain but a form of 'overcompensation' as the body restores energy homeostasis. In Traditional Korean Medicine, it is mainly explained through spleen deficiency (pi xu) and phlegm-fluid (tan yin). Extreme low-calorie or rapid weight loss weakens the spleen (pi), which normally extracts qi and nutrients from food. When the spleen is strained, it enters a state of deficiency, causing the body to inefficiently use energy and instead store fat—this is the first mechanism. The second involves phlegm-fluid: excessive carbohydrate restriction or irregular eating during a diet leads to fluid and metabolic waste accumulation, slowing metabolism and causing bloating. When normal eating resumes, this phlegm-fluid converts to fat, easily bringing back weight. In other cases, intense stress or sleep deprivation after a diet can trigger liver qi stagnation (gan qi yu jie), disrupting appetite-regulating hormones—here, psychological stability and sleep management take priority. In practice, these patterns often mix, requiring assessment of individual constitution and diet history. For example, if you originally had poor digestion and a cold constitution, spleen deficiency is more likely; if you had frequent phlegm or sticky stools, phlegm-fluid should be addressed. From my own experience, preventing yo-yo is less about 'how fast' you lose weight and more about 'giving the body time to adapt.' Aim to lose no more than 5% of body weight over 2–3 months, and slowly transition dietary restrictions back to a normal, balanced eating pattern. Herbal treatments reinforce the spleen or eliminate phlegm-fluid—Bojungikki-tang (Buzhong Yiqi Tang) series or Ijin-tang (Er Chen Tang) series are representative—but the exact prescription varies by constitution and condition, so direct consultation is essential.