Among the F1 rule tweaks for 2019 is a stipulation that a driver and their seat must weigh a minimum of 80kg.

Previously, driver weight was only included within the overall F1 car weight rules, meaning a lighter driver offered teams advantages in terms of balance placement or lower car weight overall if the design was over the minimum.

The rule change means that any team with a driver and seat under 80kg must now add ballast to make it up to that weight.

Bottas said the rules had made a huge difference to him this winter.

"Yes, I've been able to actually eat," he said. "It's quite nice to be able to gain a kilo or two. Getting pretty close to my natural weight.

"I think the regs are very good. For taller drivers it makes it easier.

"For many drivers for a long time you've had to be below your natural weight.

"It's very easy to get ill or sick. Obviously the last six years every winter I've had quite a long period of being ill.

"It was the first winter for many, many years I didn't have any flu or sickness.

"I can eat more and make sure when I train I get all the nutrients and recover well. I feel good."

In Melbourne on Thursday he explained that the previous rules had been a constant pressure.

"We do big training camps in the winter and I haven't had to think on every meal that if I have one or two calories too much it is going to make me gain weight," he said.

"So it's been really good to be able to recover well - you sleep better, feel better, feel less ill, because I think in my whole career in Formula 1 I've had to be a couple of kilos below my natural weight and then it's always fighting, fighting at the weight."

Bottas's Mercedes teammate Lewis Hamilton said last month that he had been able to rethink his training routine and focus on building more muscle mass with the flexibility the rule change offered.