Objectives: To investigate the weight loss effect of Gambi-tang in obese and overweight adults.Methods: From September 1, 2016 to December 31, 2021, a retrospective chart analysis was conducted on adult men and women who were prescribed <i>Gambi-tang</i> to address obesity and overweight in the National Medical Center (NMC). Partial analysis by age, obesity (Body Mass Index, BMI), duration of dose, and cumulative dose was also conducted.Results: The weight and BMI of the study subjects showed a significant decrease of more than 5% on average before and after treatment. In an analysis of age, significant differences by age could not be confirmed. In the analysis by obesity level, the effect of reducing weight, body fat, and abdominal fat rates in the obese and highly obese groups was greater than in the normal and overweight groups. There was no significant difference by group in the analysis by dosage period. In the analysis by cumulative dose, the greater the cumulative dose up to 1,800 g, the greater the decrease in weight and body fat. The side effect that patients appealed to the most was misjudgment, but not to a serious extent.Conclusions: <i>Gambi-tang</i> has been shown to be effective in weight and body fat loss for both obese and overweight adult men and women.