But inside his young body, there is a lot going on.
Stuart is suffering from Langerhan's cell histiocytosis (LCH), a rare type of brain tumor.
"It's not cancer, but it behaves like cancer and is treated like cancer," Stuart's father Dave said.
The tumor, which is on Stuart's pituitary gland, was found in October. The tumor has halted the production of anti-diuretic hormone in Stuart's body, and he will need hormone replacement therapy for the rest of his life.
Dave and his wife Sara first realized something might be wrong when Stuart couldn't quench his thirst.
"He started drinking a whole lot," Sara said. "Just insane amounts."
Because there is diabetes in the family, Sara and Dave worried that was what Stuart had.
A magnetic resonance imaging test (MRI) revealed the tumor.
LCH tumors fall into one of three subtypes, all of which require different types of treatment. The location of Stuart's tumor has made it impossible for doctors to determine which type his tumor falls into without doing a position emission tomography scan -- a nuclear medicine imaging technique that produces a three-dimensional image of functional processes in the body.
Without that scan, Stuart's treatment cannot begin.
The Owens' insurance company will not foot the $10,000 bill for the test, calling it "experimental."
To help raise the money for the PET scan, Mark and Sue Blake, owners of the Bon Ton diner in Bainbridge, will donate 20 percent of Saturday's sales to the Owens.
"(The Owens) are regular Friday and Saturday night customers," Sue said. "This was just a way we thought we could help them."
Sue's parents, former Putnam County residents Carlos and Barbara Bucklew, have donated a week's stay in October at their condo in Panama City, Fla., to help out. A raffle for the getaway will be held at the Bon Ton at 8 p.m. on May 2. Tickets are $10 each and can be purchased at the diner.
Histiocytosis awareness bracelets are also being sold at the diner for $4 each.
No matter what happens, Stuart will undergo chemotherapy, radiation and steroid treatments. If the PET scan happens and treatments begin soon, the tumor will likely not spread and cause any damage.
Most children afflicted with LCH are much younger than Stuart.
"He's at the extreme high end of the age range," Dave said.
Stuart, an eighth-grader at North Putnam Middle School, said he feels fine. He said his friends know he's sick, "but don't make a big thing out of it."
"That's how I feel about it, too," he said.
Dave and Sara are proud of how well their son is coping.
"He knows that it's serious, but he also knows that it's treatable," Sara said. "He's old enough that the doctors talk directly to him, so he's not so scared."
Donations can also be made at the Bainbridge branch of Tri-County Bank.
Updates on Stuart's progress can be found at www.caringbridge.org/visit/stuartowen