Prader-Willi syndrome (PWS) is a rare genetic disease, with hyperappetite and severe obesity. At present, there is no effective drugs and interventions to help control the appetite of PWS patients. More and more evidence has shown that gut microbiota is closely related to obesity. Probiotics and prebiotics can improve the structure of gut microbiota, thus improve blood lipid levels and other biochemical indicators of obese people. Therefore, this study intends to explore the effectiveness and safety of probiotics and prebiotics in controlling appetite and weight gain of PWS children.

Prader-Willi syndrome (PWS) is a rare genetic disease, with hyperappetite and severe obesity. Morbid obesity and related complications caused by hyperappetite are the most common causes of poor prognosis and death in PWS. At present, there is no effective drugs and interventions to help control the appetite of PWS patients. At present, more and more evidence has shown that gut microbiota is closely related to obesity. Probiotics and prebiotics can improve the structure of gut microbiota, thus improve blood lipid levels and other biochemical indicators of obese people. Therefore, this study intends to explore the effectiveness and safety of probiotics and prebiotics in controlling appetite and weight gain of PWS children. Participants will be divided into three groups, receiving probiotics, probiotics+probiotics or placebo treatment, and observe the changes in body weight, the structure of gut microbiota and metabolic level.

Inclusion Criteria:

• Pre-adolescent children with Prader Willi syndrome which were definitely diagnosed by gene testing.
• Consistent with the diagnostic criteria for obesity.
• Not participate in other research projects at present or three months before the research;
• Agree to participate in the test and obtain the consent of their parents; voluntarily be the subjects and sign the informed consent form.

Exclusion Criteria:

• Losing weight in ways other than the intervention measures of this project, such as taking weight loss drugs or known drugs that cause weight change;
• Use antibiotics within 1 month before the study and lasted for 3 days or more;
• Use probiotics within 1 month before the study and lasted for 3 days or more;
• Complicated with liver and renal insufficiency (alanine aminotransferase and serum creatinine indexes exceed 2 times the upper limit of the normal value set by the hospital);
• Have gastrointestinal diseases affecting food digestion and absorption (such as severe diarrhea, constipation, severe gastrointestinal inflammation, active gastrointestinal ulcer, acute cholecystitis, etc.); severe diarrhea refers to watery stool 3 or more times a day and lasts for 3 or more days. severe constipation refers to defecation 2 or less times a week with difficulty in defecation;
• Surgery was performed within 1 year before the study (except for appendicitis and hernia surgery);
• Have hepatitis B, active tuberculosis, AIDS and other infectious diseases;
• Those who are suffering from mental illness and are taking psychotropic drugs such as antidepressants.

After applying to the researcher, the researcher will decide whether to share the data