Obesity and Complications in Prader-Willi Syndrome

Obesity is the most obvious physical feature of Prader-Willi syndrome (PWS). About one third of PWS subjects who are untreated 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]
There are four recognized factors contributing to obesity in PWS:
  • Hyperphagia or overeating beginning in early childhood (between 1-6 years)
  • Decreased 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
  • An inability to vomit
These factors all play a role in the causation of obesity in PWS and require the help of specialists to manage both the 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 that are also seen at an increased rate 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 for individuals with PW. These may include:
  • Weight control through diet restriction (about 60% of normal daily caloric intake)
  • Exercise programs tailored to the individual and depending on health status, age, and jointly established goals
  • Hormone therapy, including growth hormone therapy which leads to increased height, decreased fat mass and increased muscle mass, and increased metabolic rate, and sex hormone therapy


Information & Support

For Professionals

Genetics in Primary Care Institute (AAP)
The goal of this site is to increase collaboration in the care of children with known or suspected genetic disorders. It includes health supervision guidelines and other useful resources; represents a collaboration among the Health Resources & Services Administration, the Maternal and Child Health Bureau, and the American Academy of Pediatrics.


Author: Merlin G. Butler, MD, Ph.D. - 9/2008
Reviewing Authors: Merlin G. Butler, MD, Ph.D. - 11/2014
Kyna Byerly, MS, CGC - 8/2008
Content Last Updated: 11/2014


This page was developed in partnership with the Heartland Genetic Services Collaborative 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.

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