What a load of baloney. I worked at an aluminum smelter back in the 70’s, with summertime temps on the potline surpassing 140 degrees. Hot, hard work requires salt tablets and plenty of water. It was tough, but paid well and I was skinny.
I got stuck many a July day stacking bales in a tin roofed barn. Getting out of there and relaxing in the mere 100° outside temp was a real treat. Never drank more and peed less in my life!