Boy with deadly disease competes in triathlons to stay healthy Jake Vella has rare disorder that causes him to gain weight uncontrollably.

 -- Jake Vella is literally running for his life. The seven-year-old Maltese boy suffers from an extremely rare life-threatening disease that causes him to gain weight despite his healthy diet and vigorous exercise regime. Less than 100 people in the world have ever been diagnosed with the illness called ROHHAD, which affects the automatic nervous system and endocrine system.

But Jake is no ordinary kid. To help combat the disease he competes in triathlons like his father and follows a strict diet.

“Triathlons help Jake to keep fit and active. It’s good for his health and also gives him a chance to socialize with other kids,” his parents, Josue and Maruska Vella , told ABC News.

“He leads a normal life, goes to school, plays the drums, but he has to be very careful not to get sick and we are frightened that a simple flu could lead to other complications.”

When Jake was first diagnosed with the dangerous illness at age six in 2015, it came as a huge shock to the family. Nobody else on the small Mediterranean island nation of Malta suffers from ROHHAD, so there was no playbook to go by.

ROHHAD stands for rapid-onset obesity (RO) with hypothalamic dysregulation (H), hypoventilation (H), and autonomic dysregulation (AD). It is a rare, life-threatening syndrome that affects the autonomic nervous system (which controls involuntary actions) and the endocrine system.

People with this disease may exhibit a wide range of symptoms including slow heartbeat, excessive sweating, altered pupil response to light and they also may be unable to maintain normal water balance in the body or go through early or late puberty, according to the U.S. National Institutes of Health.

Typically the patient will experience rapid weight gain in a 6 to 12 month period and may be at risk for developing certain kinds of tumors. In Jake's case it has also caused a tumor to grow on his back. There is no proven cure for the disease.

The Vellas say they just live day-by-day and hope for the best.

Jake’s video has gone viral and helped raise awareness for the disease. The young triathlete dreams about meeting Alistair and Jonathan Brownlee, two of the world’s top triathletes. Jake cannot travel because of his illness but the Brownlee brothers’ manager has been in touch following the video’s success.

Nothing is organized yet, but Jake has his fingers crossed for a shot at meeting his idols.