Romain Grosjean doesn't feel that Lewis Hamilton's vegan diet is the correct route which an athlete should go down. News ruled were brought in this year about weight, but the Frenchman feels that it's not the right way to do things.
Hamilton is still well clear at the top despite his diet and is set to seal his sixth world title this weekend in Mexico.
"I think it is a bad thing to be an athlete and follow a vegan diet, Grosjean said.
"From what I know, there have been some examples of endurance athletes who have become vegetarians or vegans and have had to stop their diets because they didn't have enough energy to exercise.
"It is no secret that I practice long-running and cycling sessions, so I need to eat substantially not only in terms of quantity"
Grosjean is 17th in the drivers' standings and the Haas driver has picked up just eight points so far this season in another tough season for the team.