I don't see much difference in both pictures honestly.
In the second picture he has a much more prominent jawline and visible cheekbones, all the tell tale signs of someone who has extremely low body fat.
It's not like he was fat in the first picture though.
1. Angle is different(rather the direction he is looking) Cheekbones and jawline are always accentuated stronger looking up than downwards.
2. Lighting is different.
3. He has longer hair in the second pic which tends to make your head look slimmer.
I am not saying you are wrong. But don't think it's the best of comparisons.
This is him in 2014 after beating Zarra's record. Even taking the hair and all else into consideration there is still a noticeable difference.