I think it was an otter.
Yeah I know, late to the party 
Ah, so you have seen Meet the Feebles.
No, wait, that was a walrus.
Well this got off topic fairly quick, but what the hell:
Well, how much weight did he loose in how long?
IIRC, the rule of thumb is that you can loose about 2.5 pounds a week safely. So figure that’s 10 pounds a month, he could in theory loose 60 pounds in about 6 months. Of course, if he was working out, he might put on some muscle, which would increase his weight somewhat, but he’d still look a lot better.
So I guess it just depends on how long it took him to get to that point.
I noticed this a few weeks ago when the trailer for his King Kong remake was shown on Channel 4 in the UK. Quite a change :eek:
After a very quick google, it looks like he got thin mostly during the shooting of Kong, and accomplished by not eating or sleeping the full time.
It looks like filming took 4 months, so guesstimating at 60 pounds lost (but probably more), probably he wasn’t at his healthiest at the end of production. 
If you look at the Production Diaries, you can see he was thin before shooting began. So he did it the healthy way.
The latest Production Diary has Phillipa Boyens, the co-writer, and she’s lost a lot of weight too. She looks great.
He went to Hogwarts?