Prader-Willi Syndrome and Complications from Obesity

Obesity is the most obvious physical feature of Prader-Willi syndrome (PWS). About one-third of individuals with untreated PWS weigh more than 200% of their ideal body weight. The paradox of the underweight infant with PWS evolving into an overweight or obese child and adult has led to considerable speculation regarding pathophysiology [Mutch: 2006] [Miller: 2006] [Holsen: 2006]

Four recognized factors contributing to obesity in PWS are:

  • Hyperphagia or overeating beginning in early childhood (between 1-6 years)
  • Reduced physical activity relating to decreased muscle tone and quantity, and increased fat mass
  • Reduced metabolic rate (about 60% of normal) related to decreased muscle mass
  • Inability to vomit
These factors require the help of specialists to manage obesity and its co-morbidities. If left untreated, the obesity can be life-threatening.

Obesity-related findings include:

  • Heart failure
  • Hypertension
  • Thrombophlebitis and chronic leg edema
  • Ulcers and cellulitis
  • Orthopedic problems
  • Abnormal lipid profiles
  • Diabetes mellitus, type II

Other findings seen at an increased rate when compared to the general population with obesity include:

  • Obstructive sleep apnea
  • Narrowing of the airway
  • Impaired respiratory function
  • Hypoventilation
  • High carbon dioxide levels
  • Increased risks of complications with general anesthesia
  • Hypometabolism

Effective strategies to prevent or limit obesity are necessary throughout the lifespan of individuals with PWS:

  • Weight control through diet restriction (about 60% of normal daily caloric intake)
  • Exercise programs tailored to the individual’s health status, age, and jointly established goals
  • Sex hormone therapy and growth hormone therapy, which leads to increased height, decreased fat mass, increased muscle mass, and increased metabolic rate

Authors & Reviewers

Initial publication: September 2008; last update/revision: July 2019
Current Authors and Reviewers:
Author: Merlin G. Butler, MD, PhD
Funding: This page was developed in partnership with the Heartland Genetic Services Network and was funded in part by a Health Resources Services Administration (HRSA) cooperative agreement (U22MC03962). We appreciate the Prader-Willi Syndrome Association (USA) for their outstanding support of individuals with PWS and their families and for the information they provide on their website – – to which we have provided several links within the Diagnosis Module.
Authoring history
2014: revision: Merlin G. Butler, MD, PhDR
2008: update: Merlin G. Butler, MD, PhDA
2008: first version: Kyna Byerly, MS, CGCCA
AAuthor; CAContributing Author; SASenior Author; RReviewer

Page Bibliography

Holsen LM, Zarcone JR, Brooks WM, Butler MG, Thompson TI, Ahluwalia JS, Nollen NL, Savage CR.
Neural mechanisms underlying hyperphagia in Prader-Willi syndrome.
Obesity (Silver Spring). 2006;14(6):1028-37. PubMed abstract / Full Text

Miller J, Kranzler J, Liu Y, Schmalfuss I, Theriaque DW, Shuster JJ, Hatfield A, Mueller OT, Goldstone AP, Sahoo T, Beaudet AL, Driscoll DJ.
Neurocognitive findings in Prader-Willi syndrome and early-onset morbid obesity.
J Pediatr. 2006;149(2):192-8. PubMed abstract

Mutch DM, Clément K.
Unraveling the genetics of human obesity.
PLoS Genet. 2006;2(12):e188. PubMed abstract / Full Text