When he spoke with Lena he did not take anything back that he said. Those are the facts.
Well, sort of. It's arguable whether he took anything back or not. He totally backpedaled and tried to the point of being obvious to avoid calling her "fat" although eventually it became unavoidable (since she brought it up).
Did he honestly have a change in heart? Maybe. Or maybe he got scared about pissing off Perez Hilton (who was mad about his comments) and was afraid of getting in a pissing match with someone who may well have dirt on his own private life. Like whether or not Stern is really bald and wearing a wig. Or whether he's cheated on Beth or his ex-wife. Or countless other things that most people are scared to bring up around Stern (except in a joking manner) but Perez may have no problem engaging in open warfare with him.
I'm 50/50 on either but it is REALLY strange the complete 180 he did, but particularly the backpedaling he did about her being fat. Especially when confronted by her on it. Normally he's more honest about a person being fat but this time he completely tried to downplay/avoid what he said earlier. Noticeably so.
Regardless of all that, the show has really taken a fall over the past few years and is but a shadow of its former self. Saying Stern is "mailing it in" wouldn't be much of an exaggeration.