In PWS, obesity (defined as increased weight for age) does not begin until after infancy which is a time when poor feeding and slow weight gain are typical. Hundreds of genes have been identified that may play a role in weight gain and obesity. Children who have unexplained, significant obesity before the age of 5 years may have a different genetic cause for their obesity. Genetic does not mean “inherited” in this situation.

When obesity occurs after childhood, there is less chance that it is due to a rare genetic condition such as PWS. Family patterns and the environment are more likely to be the cause of high weight late in childhood or in adulthood.

When obesity occurs before age 5 years, or when a child has significant relentless hunger despite enough food to eat, a genetics evaluation should be considered to rule out PWS or other recognized genetic causes of obesity.

Rare genetic disorders which cause obesity in early childhood include those associated with the MC4R pathway, for example:

  • POMC deficiency obesity
  • LEPR deficiency obesity
  • Leptin deficiency obesity
  • Prader-Willi syndrome


Other genetic syndromes associated with obesity

  • Alstrom syndrome
  • Bardet-Biedl syndrome
  • Cohen syndrome
  • Fragile X syndrome


There is information about these rare disorders at 

Tumors of the pituitary/hypothalamic region (brain) or severe head trauma

Brain tumors such as craniopharyngiomas can result in behaviors seen in PWS such as unrelenting hunger and subsequent obesity. These tumors and severe head traumas that injure parts of the brain can lead to excessive hunger. Children with pituitary tumors will have symptoms such as growth failure, thirst abnormalities, visual problems, and headaches, not just weight gain.

Butler MG, McGuire A, Manzardo AM. Clinically relevant known and candidate genes for obesity and their overlap with human infertility and reproduction. 

J Assist Reprod Genet. 2015;32(4):495-508.

Butler MG. Single gene and syndromic causes of obesity: Illustrative examples. Prog Mol Biol Transl Sci. 2016;140:1-45.

The information provided in this publication is intended for your general knowledge only and is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions 

regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read in this publication. 

Permission is granted to reproduce this article in its entirety, but it may not be reused without the following credit line: Reprinted with permission from the Prader-Willi Syndrome Association (USA), 8588 Potter Park Drive, Suite 500, Sarasota, Florida 34238 * 800- 926-4797 * 941-312- 0400 * Fax: 941-312-0142 * *