All things are relative. My most comfortable bike jacket is an EU60 and my one remaining wedding/funeral/court case suit, is a UK48 and just a bit tight across the chest and shoulders. Relative to me, he is skinny and you need to eat more Andy
I eat considerably more than you would expect for my 5'11", 11 Stone frame but it doesn't make much difference even though I'm nearer 60 than 55, so I don't think I will ever grow into the jacket.