Someone at work said you could sweat 10 pounds a day -
has anyone heard of these types of things?
Is there something factual to this or is it bunk?

lmao sweat 10 pounds a day....? are you out in the sun 24/7?? you can die off dehydration and sun damage... well to your question i believe your coworker lied to you... i live in az too... the temp can do none or slight changes to your weight.... unless you are jogging in the heat and excersing a lot...

To use your term, this is "bunk." You can sweat a lot each day but other than minimally boosting the weight you lose from water weight, it won't affect your overall health. But, you do need to be careful when exercising outside because AZ is so dry you don't realize how much water you really are losing--keep water with you at all times.

When I was younger and much more physically active, I could loose a substantial amount of weight in s short period of time... and alot of it was sweating in the heat. Now that I'm older and my metabolism has slowed down way down the only thing sweating in the heat does for me is give me a whopping headache. I think for most people the summer represents weight loss because they're out doing more. And they want to look good in less clothing. And the great garden foods are everywhere... instead of the winter comfort foods, like mac and cheese. It probably should be said that those w/o air conditioning loose weight just out of sheer misery.