"Ronaldo is fat or isn't he?" asked Lula as he spoke to the team in their hotel at Konigstein, around 20 kilometres from Frankfurt, on Thursday.
Coach Carlos Alberto Parreira replied: "He's strong, Mr President, the structure of his body has changed, he's no longer that thin boy from 1994.
"He's really had a year of difficulties including two months without playing for Real Madrid when he was injured but he will certainly by ready for the World Cup."
Ronaldo's season with Real Madrid was plagued by a series of minor injuries and he played his last match on April 8, when he limped out of the 1-1 draw with Real Sociedad on the hour with a thigh injury.
TOUGH BATTLE
Ronaldo has frequently been the subject of speculation that he is fighting a tough battle against the flab.
He said last week that the rumours no longer bother him and that he laughs them off.
Ronaldo's nagging worries have continued since Brazil began their World Cup preparations in Switzerland in May.
He limped off at halftime in Sunday's 4-0 win over New Zealand in Geneva, in which he scored the opening goal, complaining of blisters on his feet.
On Thursday, he missed training with a sinus problem.
Lula began the conference, which was witnessed by reporters, by reminding the squad that they were hot favourites.
"You must all be aware that this is a magical moment for the team," he said. "Nobody will consider that idea that Brazil will not win the cup, I've never seen such unanimous agreement in my life."
He then called on 36-year-old captain Cafu to lead by example.
"Cafu, you have to make sure these boys don't ever lose their patience ... even when they're provoked."
Lula said that winning an unprecedented sixth world title would be a boost for a nation plagued by social injustice, violence, poverty and corruption.
"It will lift the self-esteem of the Brazilian people," he said.
"You can be sure that Brazil will come to a standstill to watch you, including myself. I'll be sitting in front of the television cheering you on."
Brazil face Croatia, Australia and Japan in Group F.
(writing by Brian Homewood in Frankfurt)
