Model Case #1:
The young girl refuses to eat because eating leads to stomach pains and nausea. She is missing out on school and losing weight.
Model Case #2:
The boy is on the wrestling team and is concerned that he will not make his desired weight class in time for the competition. Therefore he goes on an intense dietary change to lose the weight.
Model Case #3:
The young student has a habit of eating several helpings of junk food upon returning home from school. He is often unaware of how much he has eaten until it is time to hide the evidence before his parents arrive home.