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genetics and weight gain for Prader-Willi syndrome (PWS)

Ask Nurse Lynn: Genetics and Weight Gain

Question:

Female, 7 years old, Unknown deletion

Does the identification of PWS by genetic testing PWS give conclusive results? In other words, your child either has or doesn’t have PWS?

Does a child with PWS gain weight event if her caloric intake is restricted? Would a “less than normal” caloric intake still result in weight gain?

Nurse Lynn’s Response:

Yes, genetic testing for PWS is conclusive —There’s no ambiguity: a child either has the specific genetic abnormality that causes PWS or they do not.

Yes, a child with PWS can still gain weight even on a calorie-restricted diet, and here’s why:

1.Extremely Low Metabolic Rate

Children with PWS have a significantly lower resting energy expenditure (REE) than other children their age and size. Their bodies burn fewer calories at rest, meaning:

  1. -Even a diet that seems “low calorie” by standard guidelines may be too much for their unique metabolic needs.
  2.  
  3. -Some children may need 25–30% fewer calories than typical children to maintain or lose weight.

2.Body Composition

  1. -Low muscle mass (which burns more calories).
  2.  
  3. -Higher fat mass, which burns fewer calories. This imbalance further lowers calorie needs and contributes to easier weight gain.

3.Hormonal and Genetic Factors

  1. -Hypothalamic dysfunction affects hunger, satiety, and metabolism.
  2.  
  3. -Growth hormone deficiency, common in PWS, contributes to lower muscle mass and higher fat storage.
  4.  
  5. -Hormonal imbalances can make fat loss and weight control much harder.

4.Food Seeking and Behavior

Even with strict controls, children with PWS may:

  1. -Find hidden food, sneak food, or consume inedible substances (hyperphagia-related behaviors).
  2.  
  3. -Struggle with rigid food rules, leading to behavioral challenges that can result in extra or unintended calorie intake.

Resources:

https://www.pwsausa.org/wp-content/uploads/2022/12/Nutrition-Adolescence-Adult-Revised-Aug-2022.pdf

https://www.pwsausa.org/wp-content/uploads/2022/12/NUTRITIONAL-PHASES.pdf

https://www.youtube.com/watch?v=-BtFDfPLonw

https://ipwso.org/information-for-families/dietary-management/

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