New six-time world champion Lewis Hamilton has admitted he put on 5 kilograms this year.

The Mercedes driver is an ardent supporter of veganism, telling the Malaysian magazine The Edge that it helps him to be a better athlete.

"I often see messages on my Instagram saying 'I need my protein because I am trying to bulk up'. Well, I just bulked up," said the 34-year-old.

"I put on 5kg this year and have gone from 68 to 73kg on a fully vegan diet."

Hamilton also cares about current social issues like climate change, and says he is involved in Mercedes' efforts to improve in the area.

"Mercedes-Benz is a huge organisation and I have got a phone call with the CEO later today to discuss how we can work on getting rid of all the leather supplied to the cars," he said.

"I want to be part of a system that is going to help heal the world and do something positive for the future."