Lewis Hamilton says he has put on 5 kilograms because the weight rules have been changed for 2019.

A regular on magazine covers, the five time world champion has admitted he has enjoyed the relaxation of the rules.

It's the same story with many other drivers, who have put on between 1 and 2 kilos over the winter.

"Oh, it's more with me. But I'm still within the limit, so everything's fine," Hamilton said.

He says he only put on muscle, but admitted he indulged in "pancakes and Cheetos".

"I am not trying to be the Hulk, but it takes time to put on muscle in the right way and it has been great to eat bigger portions," said the Mercedes driver.

"I feel in the best shape I have ever been and can lift more weights."