Researchers at the University of Hong Kong found those from low-income backgrounds had a 30 per cent higher chance of having a weight problem, compared to those from wealthier families.
They interviewed 10,000 students from 400 secondary and primary schools. Study leader Professor Patrick Ip, from the department of paediatric and adolescent medicine, said less-privileged families tended to feed children low-cost, fatty food.
While these types of meals are filling, they increase a young person's chances of becoming overweight.
"Parents of low-income families work long hours, leaving them with limited time to take their children out for exercise," Ip says. "They also have less knowledge of how to prepare healthy meals."
Ka-yan is an eight-year-old student at Fresh Fish Traders' School at Tai Kok Tsui. She is 1.37 metres tall and weighs more than 40 kilograms. That makes her body mass index (BMI) 25, which is considered overweight. She lives with her family in a subdivided unit in Sham Shui Po, and her dinner usually consists of pork, fish and preserved vegetables.
"We cannot afford fresh vegetables. We only get fruit when Ka-yan takes some from school. Her father works long hours and only takes her outside to play on Sundays," says Ka-yan's grandmother, who cooks her dinner every night.
The school principal, Leung Kee-cheong, says many low-income families buy cheap frozen meat because they cannot afford fresh fruit and vegetables.
"Parents like to deep fry food to get children to eat more. They also feed them bread and instant noodles to make them feel full. To help our students lead a healthier life, the school provides them with fruits every week," he says.
Lawmaker Kwok Ka-ki wants the government to subsidise sporting activities for low-income families.