This simply means that people with cancer are less active than healthy people because they get tired quickly or are in serious pain - both of which I can confirm.
You need to read up on the Miocene warm period - millions of years when the earth was mostly tropical and there were no cavemen with AC or SUVs warming the planet. Us monkeys have only been around for a few hundred thousand years.
I am in Central Europe. It is 38C outside and 27C inside. We went to swim in the local lake earlier and now I wear a wet T-Shirt. A wet shirt is not 'cold'. It just keeps you comfortable.