Prader-Willi Syndrome (PWS) is a rare genetic disability with a prevalence rate of 1 in 10,000-30,000 live births. 1,2) PWS is a complex developmental disability caused by a deficiency of genes expressed on chromosomes 15q11-q13, 3,4) resulting in growth hormone (GH) deficiency, hypogonadism, reproductive dysfunction, behavioral problems, hyperphagic problems, and obesity. 5,6) The cause of the abnormal body composition in PWS is not completely known. However, a unique pattern of body composition with increased body mass index (BMI) or total body fat mass (FM) and a decrease in lean body mass (LBM) has been observed in patients with PWS. 7) Individuals with PWS may have pathological obesity resulting from excessive weight gain or severe hyperphagia. 8) Physical deterioration and weight gain in patients with PWS can cause negative consequences such as metabolic dysfunction, cardiovascular disease, and early death. 8) There are pharmacological and non-pharmacological methods for treating these complications in patients with PWS. Nonpharmacological methods, such as dietary restriction or bariatric surgery, have limitations in improving the condition of patients with PWS. 8) In contrast, although they are nonpharmacological treatments, dietary interventions have been reported to be effective in preventing excessive weight gain. 9) However, another study has reported that nutritional intervention