The minimum weight of a car has increased from 733kg to 740kg for the upcoming campaign.
But more importantly, at least 80kg of that must be made up of the driver, his seat and driving equipment.
It is rumoured Hamilton has increased his weight by 8kg to make up the difference.
The Brit has been more relaxed than usual with his diet in the build up to the season.
Hamilton is hoping to win his sixth world title with Mercedes this term.
And he is feeling comfortable with his body composition.
“For me it is much more,” Hamilton told Motorsport Magazin of the weight rule changes.
“I’m heavier, although I do not eat sweets often, of course I could eat whatever I wanted during the break, but I always remained very active.
“I’ve enjoyed training more than ever before. It used to be less fun, but if you can make it interesting and different It’s something else.
“I’ve been pretty clean since last month. Body fat is dwindling, I’m more defined and have more efficient muscle mass, I’m not trying to be the Hulk because of course it takes time to build muscle, but it was great to be able to eat whatever you want.
“The seat was really interesting, we did not have to adjust much, although I’ve gotten a lot heavier, which will certainly go a bit up and down over the coming weeks, but all that’s left is to keep the shape and hit the ball stay.”
Meanwhile, Haas driver Romain Grosjean also spoke of his happiness of the rule changes.
“I was 68 kilograms last season, now I weigh 73 kilograms, in the morning,” he said.
“I feel stronger now, I do not know if I need it in the car, but in any case in life.
“It was not great to starve yourself down and not be able to eat as you please.”