I don’t think resisting/negating the poison was done by changing weight as such, just another aspect of total bodily control.
ryu hayabusa
changing the size of your body assumingly changes the size of organs needed to absorb poison such as the liver, that’s why it takes bigger doses of tranq darts to knock out elephants. The size of them and all :p
Wereael
While it may be possible that she resisted the poison by changing her weight, it’s not definite until confirmed in-comic, unless Aria wants to step in. It’s a good theory though.
ryu hayabusa
till then I suppose xD
Aria
As far as these two particular functions go, they’re pretty much unrelated! “Changing her weight” is adjusting how her body’s physical manifestation is affected by outside factors, so she’s expending energy against the atmosphere’s to make herself more buoyant or more heavy. “Negating poison” is more internal, either accomplished by bolstering her metabolism to filter it out or, if it’s something especially lethal, slowing the speed that she processes it until she can get help.
So, while it looks pretty cheap from the outside, most of a commanders’ tricks are just using energy to fight their environment’s effects on them, not actually impervious to damage or poison or any of the things they like to claim. It also takes a proportional amount of power to accomplish all this, which might end up being harder on the body than the original assault was.
He probably means total body mass, which is how she would be lighter and heavier. People that weigh more in general are more resistant to drugs, poison, and have a higher tolerance for alcohol, among other things.