The Mexican had bulked up over the winter to better cope with the more physical nature of 2017's cars, but has been asked by his Force India team to trim off some weight because its new challenger was too heavy in testing.
"I have tried so hard to lose weight in the last couple of weeks since Barcelona," said Perez, who has already lost more than two kilos since testing finished.
"Obviously I increased my weight from last year purely by training harder, putting on more muscle, but I was on an extreme diet all last week and still now until Saturday [I will do the same].
"I am all the time very hungry. As much weight as I can lose, the better it will be for us."
Perez said the issue of car weight had come up at Barcelona, but the team would only find out properly in Australia just how much it needed to lose.
"We haven't weighed the car actually, because in testing you have a lot of sensors and things on the car," he said.
"Right now, considering that I lose two kilos or three since Barcelona, then probably we might be quite close."
Perez was confident, however, that the weight issue would not affect Force India for long, as fixes would be in place by the Bahrain Grand Prix at the latest.
"I think the weight, sooner or later we will be on it," he said. "If not this weekend, then latest by Bahrain, so I don't think that is a big issue."
Third still possible
Perez believes that Force India has the platform to challenge strongly again in 2017, but says it will not be starting the season in the perfect position.
"The objective is still to finish third, to move up," he said. "What we have seen in winter testing is that we are not at the level that we would like to be to start the season.
"But I think this year – especially this year – the upgrades we are going to have, not only us but the rest of the teams, are huge. So I am still very optimistic.
"It is not important where you start, it is where you finish. The season is very long and I am still very optimistic and very confident that the team will do a great job this year."
Source: www.bing.com