Prader-Willi Syndrome Macronutrient Study
Prader-Willi Syndrome Macronutrient Study
The overall objective is to explore the mechanisms by which macronutrients regulate food
 intake and weight gain in Prader Willi Syndrome (PWS).

 Previous studies from the investigators' labs suggest that the increased appetite of PWS may
 be triggered or maintained by an increase in the levels of ghrelin, an appetite-stimulating
 hormone produced primarily by the stomach. This study will compare the effects of low
 carbohydrate diet versus low fat diet on levels of ghrelin, appetite suppressing hormones and
 markers of insulin sensitivity in patients with PWS.

 The investigators hypothesize that the low carbohydrate diet will suppress plasma active
 ghrelin and increase appetite-suppressing hormones to a greater degree and for longer
 duration than the low fat diet and will thereby reduce hyperphagia and increase satiety. The
 investigators also hypothesize that the low carb diet will improve hormonal and metabolic
 markers (fatty acids, amino acids and organic acids) of insulin sensitivity and inflammatory
 cytokine profiles of children with PWS.
Inclusion Criteria:

 -  diagnosis of Prader Willi syndrome confirmed by chromosome analysis (ie. interstitial
 deletion of paternally-derived chromosome 15q, uniparental maternal disomy or other
 chromosome 15 abnormalities)

 -  age 5 years to 17 years

 -  written informed consent and assent obtained and willingness to comply with the study
 schedule and procedures

 -  free T4, TSH values in the normal range (either endogenous or with thyroxine
 replacement)

 -  weight stable (BMI percentile fluctuation of <5 percentiles) over the preceding 2
 months prior to the study

 Exclusion Criteria:

 -  presence of other clinically significant disease that would impact body composition
 including diabetes mellitus, chronic inflammatory bowel disease, chronic severe liver
 or kidney disease or neurologic disorders

 -  concomitant use of medications known to affect body weight or investigational drug in
 the past year