I heard that diet pills can cause irregular periods. Why exactly does this happen?

From a physiological perspective, the body is conservative; when energy levels drop sharply, it concludes that it is not an ideal time for reproduction and temporarily suspends menstrual functions. In Western medicine, this is seen as an overload of the hormone regulatory axis. In Traditional Korean Medicine (TKM), this aligns with a state of 'Blood Deficiency' (血虛), where essential blood and nutrients are insufficient. Furthermore, if diet medications overstimulate the sympathetic nervous system, the body's energy (Qi) becomes unbalanced, preventing nutrients from effectively reaching the Lower Burner (下焦, the pelvic region). When this is coupled with the accumulation of 'Blood Stasis' (瘀血, stagnant blood) or 'Phlegm-Fluid' (痰飮, metabolic waste), circulation around the uterus slows down, resulting in reduced menstrual flow or delayed cycles. Rather than relying solely on extreme calorie restriction or potent medications, it is crucial to assess your overall vital energy. If you have a 'Spleen Deficiency' (脾虛, impaired digestive and absorptive function), you may be more susceptible to these side effects. It is essential to adjust your approach by evaluating your current state of circulation and systemic balance.