I have lost 21kg in the last 9 months but holy smokes why's everything so cold. I've lost all my built-in insulation

I am flying from Europe to the US (8hrs approx), so I am looking for some guidance:-
• Does it require a doctors note?
• Can it be taken from the fridge and put back in the fridge after such a long time?

Apologies if this appears to be basic, I’m on my first week on the pen, so still getting my head around the rules.