But it's all good with the NRL club, who has given the five-eighth their blessings to eat anything he likes this pre-season.
The NRL's breakout star of 2024, 19-year-old Galvin is busy hatching a plan to avoid second-year syndrome as he awaits the arrival of his halves partner to pre-season training in the new year.
So far, that plan has not involved consulting with four-time premiership-winner Luai, whose highly anticipated arrival at the Tigers was delayed by Samoa's tour of England.
"I haven't spoken to him at all yet," Galvin said of Luai, who is tipped to help reverse the Tigers' fortunes after three consecutive wooden spoons.
"I think he's going to come back a little bit before Christmas and in the new year he'll start training again.
"We know how good of a player he is, he'll take so much pressure off me. He'll run the team, do what he needs to do and I'll just play off the back of that. Whatever he wants, I'll do."
In the meantime, Galvin has set himself a goal to improve his fitness and has already shaved three seconds off his 1.2km time trial, which he now runs in four minutes 12 seconds.
"I'm pretty impressed with that," he said.
"I think if you work hard, good things happen on the back of that.
"(Second-year syndrome) is why I've come back fitter this year ... I don't want to worry about that second-year syndrome."
Packing on size is also a top priority for the naturally rangy Galvin, who is no longer an unknown quantity for opposition defences and will be targeted if he remains lightweight.
Galvin has shot up two centimetres since the winter, now standing at 193cm, but putting on size in the other direction has been more difficult.
The five-eighth has only been able to put on one kilogram so far, but is hopeful the Tigers' new diet plan will change things.
"I don't eat enough. Every morning I'm in here, they tell me, 'Eat breakfast, eat lunch', they watch me eat and that. I've got to put the kilos on. I struggle with that but I'm trying my best," he said.
"The dietician Clare (Flower), she says, 'Eat what you want, Lachlan', so it's pretty good."
Galvin isn't worrying about hitting calorie targets, instead putting his faith in Ronald McDonald to guide him.
"I get a dinner box from Maccas on the way home,' he said. "That's why I love playing."
"Clare spoke something about that (calorie target) but I don't even know what that means. I didn't really listen at school that much.
"I'll just try eat as much as I can. If I come in the morning and I weigh more than I did yesterday, I'm happy."
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