XUZHOU (Jiangsu) • A young Chinese boy touched the hearts of many when he put on around a third of his weight in less than two months, in a race against time to donate his blood marrow to his leukaemia-stricken father.

Cao Yinpeng had just turned eight when he learnt that his father was dying from leukaemia as doctors could not find a suitable donor to perform a blood marrow transplant - his father's only hope to survive.

The boy was a match for his father, Mr Cao Lei, a clerk from Xuzhou in eastern China's Jiangsu province. But tipping the scales at just 35kg, Yinpeng was 10kg too light to meet the minimum donor weight requirement.

While China's marrow donor programme website stipulates that donors should be aged between 18 and 45, exceptions are sometimes made for younger donors to save the lives of family members.

Earlier this year, Yinpeng stopped going to school to focus on fattening up before the bone marrow transplant in July, China's CCTV news reported.

With help from his family, he devised a plan to meet the 45kg weight requirement which would enable his body to produce enough blood.

He increased his food intake and kept fit by doing brisk walking for an hour every evening. He avoided strenuous exercise.

In the days leading up to the transplant, Yinpeng had to endure several sessions of blood collection - to ensure a steady supply of fresh blood for his father - and having chilled blood pumped back into his body.

In one session, doctors spent five hours drawing 800ml of blood from his body and infusing him with another 500ml of blood.

The blood marrow transplant in July was a success. Mr Cao is reportedly on the road to recovery and Yinpeng has since learnt how to cook to better take care of his father.

"My father gave me my life. I want to give him back his life too," Yinpeng was quoted as saying in local reports.

Weibo user Zheng Qing said it was hard to believe these words came from an eight-year-old.

"Even a child knows how to repay his parents. Grown-ups like us should do better."