You might find going to the gym a hassle, but what if you had a personal trainer in your pocket?

This is what Kurbo - a mobile app to help people manage their weight - is designed to be.

The company, which is based in the United States, has been working with Singapore's Health Promotion Board (HPB) on two pilot projects involving 220 children from 15 primary and secondary schools.

After a three-month trial, seven out of 10 children lowered their body mass index scores to a healthier level, an HPB spokesman said.

He added: "Six out of 10 participants ate healthier by consuming more fruit and vegetables, and increased physical activity.

"Their parents were confident that they and their children will continue the positive lifestyle changes made."

The app allows children to track fitness goals - including meals, weight and exercise - in order to reach personal targets. Once a week, they meet their fitness coach via video calls to set up new goals for the weeks ahead.

Kurbo co-founder Thea Runyan said: "We incorporated a lot of important behaviour modification strategies. Our goal was to make this fun."

Gilbert Yong, eight, joined the programme last year when he was in Primary 1. His mother, Mrs Wiliana Yong, said that Gilbert has become a lot more aware of what he is eating after encouragement from his coach.

"Before, it was very difficult to move him away from snacks, especially the sweet stuff," said Mrs Yong, a lecturer.

"But (the coach) taught Gilbert how to read food labels, and now he is very conscious... For example, he knows that a certain product has a lot of sugar."