It happens frequently to people who are in a very hot environment. Despite drinking lots of water, they still get sick, because they've been sweating a lot, and just drinking water doesn't replace the essential salts your body needs. This happened to the teenage son of some friends. He was in Japan with a group of folks, it was July, hot and humid. The tour leader reminded them to drink lots of fluids, but this boy didn't like the taste of the energy drink, so he just had water. He dropped like a stone a few days into the trip. Fortunately, they knew what was wrong and got him right in just a few hours.
When our daughter and I were in Tokyo visiting friends, it was late July, early August. Although the temps were only in the mid 80's, it was extremely humid and you'd sweat profusely. I thought it was just because I was overweight, and we were doing a LOT of walking. Then I noticed the little bitty Japanese women walking around with bottles of Porcari Sweat (an energy drink with salts in it), a fan and a little washcloth to wipe the sweat from their brows. I didn't feel so bad after that! ;o) The great thing is that just about every third street corner, you'll find a vending machine selling the energy drink, or sodas, or water. Heck, there are some places where right next to the machine selling water, there are vending machines selling BEER! Tastes REAL good on a hot day, I can tell you! ;o)
BTW, I saw Marie on "Dancing with the Stars" and she looked in perfect shape. Not too thin and certainly not fat. Some women on TV look so thin like drug addicts.