But while his puppy fat may seem sweet, Coleman is now concerned about his weight.
The 10-year-old, who made his debut in the TVB series The Money-Maker Recipe, is 1.43 metres tall and weighs 46.5 kg. This makes his Body Mass Index 22.6.
For his age, 23 is considered obese, according to the Centres for Disease Control and Prevention in the United States.
Coleman admits that he loves high-fat food like cheese and ice-cream. But he knows he's got to start making better choices.
"I considered myself a fatty and I am seeing a dietician. I was asked to cut down on fatty food," he says.
"Now I bring cereal to school as a snack."
Coleman is not alone in the struggle to maintain a healthy lifestyle in Hong Kong.
A recent international study found that under-18s in Hong Kong are less fit than their peers in the West.
Researchers at the University of South Australia studied the cardiovascular fitness of youngsters aged between nine and 17. They found that, on average, they were 15 per cent less fit than their counterparts between 1970 and 2010.
The decline in fitness was twice as high in Asia, where participants were 30 per cent worse off than their peers in the 30-year period.
Researchers measured how fast and far the youngsters could run in five to 15 minutes. On average, today's children took 90 seconds longer to run about 1.6 kilometres than their counterparts did 30 years ago. The decline was seen in boys and girls across all ages.
Coleman is not surprised by the results. "Local youngsters are privileged and can eat whatever they want," he says. "This, coupled with the heavy pressure from homework, does not leave enough time to exercise. It adds up to being less fit."
The Primary Five student, from Ma Tau Chung Government Primary School (Hung Hom Bay), adds: "I only get physical education lessons twice a week - it's definitely not enough."
Dr Lobo Louie Hung-tak, an associate professor at Baptist University's department of physical education, says the overprotective nature of parents doesn't help.
"Swimming, cycling and running are good aerobic exercises. But many school children just do not do them ... some parents consider swimming dangerous," he says. "Thus, many schools do not have swimming lessons to avoid receiving complaints from parents."
Louie believes parents often prefer their offspring to engage in "structured activities".
"They may arrange for their children to play music, because this could help them get into good schools," he says.
Louie also thinks young people aren't encouraged enough to work out. "Many parents don't like their children doing sports, considering them a waste of time."
His department recently found that 20 per cent of secondary school students did not know how to ride a bicycle and 47 per cent did not know how to swim.
"Young people can be fit in different ways. They can be skilful, like a tennis player. But not all types of fitness relate well to health," Louie says.
"The most important is cardiovascular fitness, which is the ability to exercise vigorously. You don't have to be an Olympic star to do sports. Parents should inspire youngsters to exercise regularly."
Additional reporting by Ng Kang-chung