Behaviourally, children with Prader-Willi Syndrome tend to be floppy, sleepy and passive in the first year. Their muscle tone begins to improve towards the end of the first year and they become more active and alert. These are often related to the insatiable desire to obtain food, which develops between one and four years of age and is accompanied by excessive or rapid weight gain, and is physically, emotionally and socially debilitating. Excessive intake of food may cause life-threatening obesity and often involves foraging for food, stealing and hoarding food. Research shows that people with Prader-Willi Syndrome think a lot more about food than other people, and may continue to eat at a steady rate as long as food is available.
Dietary management is the corner stone of managing the obesity.
Typically, carers have to limit access to food and take over total control of food intake. Behaviour modification methods which rely on reinforcement and self-monitoring as part of weight control and exercise programmes, are also required. Long-term maintenance of weight loss is difficult to achieve, and problems with weight control can become worse in adult life when, with increased independence, food is more readily available. Outbursts of rage and aggression, stubbornness and belligerence, are common in affected individuals, beginning around age three to five, becoming more marked later in childhood and persisting into adulthood. They may be over friendly, with impulsive chatter, but most are also reported to be immature and socially isolated.