Galan007
|Quantum Observer|
During his fight with T&A, Galactus sustained heavy damage--his armor was devastated, and he was 'bleeding' cosmic energy:
http://imgur.com/6gkCCzF
http://imgur.com/YgVPx8h
http://imgur.com/dv3jVbd
http://imgur.com/cPqHbeD
http://imgur.com/OfsstQV
When Galactus was retrofitted with the tech Thanos devised to weaponize him, the 'bleeding' was stopped/siphoned into the machine, but his armor was still in a state of disarray:
http://imgur.com/ItS9fZx
Furthermore, it was outright stated that Galactus was starving whilst being used to Annihilus' whim, as he was only being fed "a trickle" of cosmic power--just enough to keep him alive:
http://imgur.com/Od79xHg
And all of the cosmic power from the planets he destroyed was being siphoned into the canisters:
http://imgur.com/Mcc94th
(Essentially those canisters contained the energies of numerous worlds.)
That being said, when Galactus first awoke from his imprisonment, he still looked like complete shit:
http://imgur.com/LidHShT
But when we next see Galactus, he looks very healthy(his armor and injuries are repaired), and the cosmic energy canisters are circling him:
http://imgur.com/KCtOu6j
He then goes on to unleash a galaxy-spanning wave of omnidirectional destruction:
http://imgur.com/RCxDXCG
http://imgur.com/2ja58qc
http://imgur.com/xCl8eEb
In a nutshell: given the overall magnitude/scope of the 'HMR' blast+Galactus' general appearance before and after we see the canisters encircling him, I think it's safe to assume that he was not only feeding on them, but that the energies within them were sufficient to replenish him--remember, cumulatively they contained the cosmic power of multiple planets, so Galactus being satiated from them shouldn't be out of the question, imo.
I find it that far more likely than believing that a less-than-well-nourished Galactus is responsible for preforming what is arguably his greatest on-panel display of power to date(ie. a galactic attack.) /shrug