Lack of Satiety: It’s Not Just About Food   

Linda M. Gourash, Janice L. Forster

Pittsburgh Partnership: Specialists in Prader-Willi Syndrome, Pittsburgh, PA

Lack of satiety is the preferred term for the appetite disorder of PWS, yet many persons continue to assume that the ability to eat large amounts of food means that persons with the syndrome experience severe hunger.  Several clinical observations argue against this and even suggest that hunger as well as satiety may be blunted/reduced:

.                       •           Infants with Prader-Willi syndrome are disinterested in food and cry very little. Anorexia with excessive weight loss has been observed in a number of older patients with the syndrome.

.                       •           Persons with the syndrome under continuous inpatient observation appear to tolerate low calorie diets and steady weight loss. They express satisfaction with their food when they are given large portions of low calorie foods and complete assurance of what each meal will contain in advance (part of Food Security).  Most patients “buy into” the diet accepting it pleasantly, proud of their weight loss.  They will still forage opportunistically and require the usual precautions. Families report success in sustaining patient satisfaction at home using Food Security Principles.

.                       •           “Hunger strikes”, sometimes prolonged, have been observed repeatedly in patients who object to exercise or other demands (but so far not over the diet).  

Further, a number of typical behaviors seen in PWS suggest a disordered appetitive drive not specifically related to satisfying nutritional needs:

.                       •           Overuse of nonnutritive flavored beverages

.                       •           Overuse of both smokeless tobacco and cigarettes

.                       •           Overuse of nutritional supplements, over-the-counter medications

.                       •           Overuse of salt; sweeteners  

Other behavioral characteristics can also be understood as a failure of somatic or other modifying feedback

.                       •           Altered pain awareness

.                       •           Skin picking

.                       •           Collecting excessive numbers of CDs, Videos, Beanie Babies etc.

.                       •           Hoarding unlimited amounts of pens, papers, markers, etc. (including food that is never eaten)

.                       •           Overuse of shampoos, conditioners, creams, lotions etc.

.                       •           Perseveration/arguing

.                       •           Incontinence

 Conclusion

These traits may all represent a failure in modifying feedback pathways.  Consideration should be given to the possibility that the neural basis for the food satiety disorder and for the behavioral traits of PWS is one and the same and is not specific to the weight regulation mechanisms centered in the arcuate nucleus of the hypothalamus.