Prader-Willi syndrome (PWS) is a genetic disorder characterized by low muscle tone, short stature if not treated with growth hormone, incomplete sexual development, and a chronic feeling of hunger that, coupled with a metabolism that utilizes drastically fewer calories than normal, can lead to excessive eating and life-threatening obesity. The food compulsion makes constant supervision necessary. Average IQ is 70, but even those with normal IQs almost all have learning issues. Social and motor deficits also exist. At birth the infant typically has low birth weight for gestation, hypotonia (weak muscles), and difficulty sucking due to the hypotonia which can lead to a diagnosis of failure to thrive. The second stage ("thriving too well"), has a typical onset between the ages of two and five, but can be later. The hyperphagia (extreme unsatisfied drive to consume food) lasts throughout the lifetime. Children with PWS have sweet and loving personalities, but this phase is also characterized by increased appetite, weight control issues, and motor development delays along with some behavior problems and unique medical issues.