Don't recall it saying anything specific just that it was a traumatic moment for "the group" and they killed the boy and buried him, but they did mention that... It was in the wiki about the show I was reading. To be honest though, similar things have been shown in the show... Zombies in the church seemed a little slower and more decayed, Bicycle Girl (despite having no lower torso) was noticeably unable to grab quickly or be too aggressive... The Wiki seems to point out a few things from the comics but I haven't read them yet myself.
Kirkman says they're instinctively eating though, not a need per se... They're pretty dumb and primal... Milton I'm quite sure is who mentions them starving to death but they may just simply become more lethargic as they're decayed further too. I think that makes sense for the most part.
They didn't mention time-frames for the decaying in anything I read... Years, decades... It's shown on the show though, clearly. Don't know about the comics but one of the wiki things mentioned pure white eyes as the iris and eyeball decayed is a sign of the zombies decaying over time in the comic.
The wiki contradicted itself (and the show, at least) on the "lurker" thing and kept saying they were "playing dead"... I don't see that. Dormant maybe after not finding food or stimulation for a while, but some of them in the show clearly are waking up slowly to move to what got their attention... others woke up quickly and attacked immediately.
Mazara outright said they are NOT starving but are decaying in a Q&A that came up in the search, but here's a quote from the Wiki:
In "Walk With Me", it is revealed that zombies starve, but at a significantly slower rate than humans. When a living person goes into starvation mode from lack of nourishment, their body begins breaking down fat tissue, followed by muscle tissue and converting it into energy. Eventually, the body will begin breaking down the tissue of vital organs and the person eventually expires when those organs cease to function. In theory, if a zombie cannot find a food source, the zombie pathogen will probably cause a break down of body tissue and convert it into energy even though they are dead, until they basically wither away to nothing.
I think this is where Milton says it, but again I think he could just be witnessing decay... or perhaps the food makes them more vibrant and a lack of food makes them more sluggish, but not dying of starvation?
The wiki says they can climb ladders and, I don't know about you guys, but I don't recall them climbing anything. If anything, I recall them NOT climbing up after Rick and Glenn in Downtown Atlanta.
Here's more on eating habits...
Zombies prefer to eat living flesh: birds, animals, and people. If living food isn't available, zombies will eat meat from dead corpses, unless, in the case of humans, the corpse reanimates as a new member of the undead. Zombies do not digest food. When their bodies are "full", the undigested meat will be forced out through the anus. As zombies are dead, it is assumed that their bodies will continue to rot even if they are well-fed. If no sustenance is available, zombies will starve, ultimately contributing to the rate of decomposition. Unlike humans, however, who can only live several months without food and a few weeks without water, zombies can survive for perhaps years without any nourishment.http://walkingdead.wikia.com/wiki/Zombies
There are some citations to specific notes from the show and comics...
I knew someone on the show mentioned them starving, but the show's so widely separate of the comic at this point who knows.
Issue 55 seems to mention something about a "malnourished walker" the group encounters, as well, but I can't find much more than that.