His love of his grandmother's food, which featured plenty of sugar, cream, fat and rotis (flatbread), and his lack of exercise, meant he was not just chubby, he was obese, weighing in at 90 kilograms before he hit his teens.

That is four kilograms more than his weight when he became India's first Commonwealth Games javelin champion at Gold Coast 2018.

He followed that up at Tokyo 2020 by becoming India's first Olympic champion in any athletics event, after which his popularity soared to such a level he found himself with more than four million followers on social media.

That is quite a rise for the son of an agricultural worker from a village in Haryana state in northern India.

His size as a child played a role in Chopra's introduction to athletics. His father signed him up to a gym in a local town and he moved on to Panipat, a nearby city where he first saw athletes throwing the javelin.

When Chopra tried it himself he could throw more than 40 metres with no training or knowledge of technique. It was clear he had a special talent, which was spotted by another javelin thrower, Jaiveer Choudhary.

"I started with Jaiveer - he supported me a lot when I knew nothing about javelin," Chopra said in one of the countless interviews he has given since becoming the biggest individual sports star in India. 

"He is coaching in the national camp now. He is very dedicated. Training with Jaiveer helped me improve my basics.

"In athletics, you develop slowly. Javelin is a very technical sport. I rectified my faults over time. Then I trained under foreign coaches who further rectified my errors. My coaches have helped me a lot. All that support has brought me here."

As a teenager Chopra improved to such an extent that he set a national record within two years, and a junior world record in winning the junior world title in Poland, a feat that shot him to fame overnight in 2017.

When he arrived in Australia for Gold Coast 2018, Chopra was a 20-year-old Commonwealth Games debutant, but was favourite for gold.

He won it in style, with a seasonal best of 86.47m, ahead of the Australian Hamish Peacock and perennial rival Anderson Peters, from Grenada, who became world champion in 2019.

His victory in Gold Coast, another landmark for Indian athletics, earned Chopra the honour of being his nation's flagbearer a few months later at the Asian Games in Indonesia, where he also won gold.

The Commonwealth Games is a major event in India, and his victory also led to Chopra winning the Arjuna Award, a prestigious honour for outstanding performance which was presented to him by India's President, Ram Nath Kovind.

Now Chopra wants what Peters has - the world title - and more besides.

After victory in Tokyo, he said: "I am not going to be content with this Olympic gold and sit on this laurel. 

"I would like to do even better and win gold again in the Asian Games, Commonwealth Games and again in the Olympics."

One thing is for sure - he will be one of the biggest attractions at Birmingham 2022.