This must have been one of Adam’s most grilling interviews ever.

32-year-old Adam and his girlfriend were down at The Howard Stern Show, where he ended up in an awkward discussion about Aguilera’s weight.

And we all know how much we hate talking about our weight…

Since the birth of Christina’s son, she has been struggling to lose the extra baby fat from her pregnancy. And over the past year she has been getting criticism from everywhere – if it’s not her body, it’s her fashion flaws too.

Stern said:"This is a sensitive subject for women, but why do you think she's gotten so heavy? …Is she upset? ... She used to be so f***ing hot ... And her clothes are too tight, right?"

"Her clothes are tight. She likes to wear tight clothes," Levine said. "She clearly likes to talk about being comfortable with being a woman and snapping her fingers and doing the whole thing.”

At one time Kelly Osbourne, who herself has firsthand experience with struggling to lose weight called Christina a “fat c*nt”.

I guess Adam probably figured discussing Christina’s weight was going to have bad consequences because when asked what size Christina is, he cleverly replied: "I'm keeping my f***ing mouth shut."

And he should.  It’s not fair to have a friend/colleague go on radio and start talking about such a sensitive subject.

Check out the interview clip below.

Christina Aguilera should: