A recent survey suggests the proportion of children who are overweight or obese in Hong Kong has more than doubled during the pandemic.

At a press conference on Thursday, researchers from Chinese University's medical school and the Paediatric Foundation said they polled more than 1,400 parents of kindergarten and primary school pupils earlier this month.

Eight out of 10 respondents said their children spent less time playing outdoor sports since the pandemic began, while half of them said their children ate more snacks and sweetened beverages.

As a result, the proportion of overweight and obese children rose from 4.8 percent before the pandemic to 13.5 percent, the researchers said.

For children aged between nine and 13, there was an increase from 7 percent to 24 percent.

Dr Lilian Wong, secretary-general of the foundation, said older children tend to have worse eating habits.

"This is why... we have to grasp the opportunity to teach younger students or children that they have to eat healthily. This is also an opportunity for parents to change their practice right now, otherwise when the children enter primary or secondary school, it will be very difficult to control their behaviour," she said.

The survey also covered how happy children are, with a happiness index falling from 8.51 out of 10 to 6.75 since the pandemic began.

"Obviously there are so many reasons why they are unhappy, like not being able to go to school and see their friends, and unable to go out and play, and seeing their parents all the time, being nagged," said Professor Albert Li, chairman of the paediatrics department at Chinese University.

Wong said the findings indicated that the more stressed parents were, the less happy their children would be. She said parents should pay attention to their own well-being while taking care of their family.