Valtteri Bottas has counted himself as not among those drivers who are dieting hard ahead of the 2016 season.

Red Bull's Daniel Ricciardo admits that he was told to lose 5kg before Melbourne, while Toro Rosso rookie Carlos Sainz slammed the pressure put on drivers by the regulations to be lighter than is healthy.

"It's not safe and not the right way to go," Sainz told Reuters. "We like to be fit and thin, that's our job, but it's not our job to be extremely skinny."

Meanwhile Bottas, who according to some reports dropped from 70kg to 67kg for the start of the heavier 'power unit' era in 2014, said that Williams is no longer asking him to drastically diet.

"I am no longer eating plain lettuce," he told Finnish broadcaster MTV.

"2014 was the most difficult year for weight but it is not any problem this year. I am at a good weight for me.

"It's a long season and you have to find the limit under which it makes no sense to go with your weight. So now I get to eat more than salad."

Bottas was also upbeat about his general physical condition, having missed the season opener in Melbourne a year ago with a back injury.

"I do special training for it that is now part of my routine," he said. "Physically I am in good shape overall and more ready than any other year."

The 2016 season begins with the Australian Grand Prix in Melbourne on March 20.