What's a "Hanshin yoku"?

So recently, my wife heard that doing "Hanshin yoku" is good for a diet. What is that, you might be asking yourself?
Turns out it's just a bath that's not completely full. All you have to do is fill the bath so the water comes to about your belly button. The temperature should be between 38 and 40 degrees Celsius (100 to 104 degrees Fahrenheit).  You should try to stay in it for about 30 minutes. Just make sure you keep the top half of your body out of the water. This way you'll sweat a lot.
It's basically like a home sauna. I don't know if it really helps, but the days we do it, I usually see some kind of weight loss the next day. So why not give it a try. Get a good book, jump in the bath and relax for half an hour.