The scientific way to lose weight

Forget about pills, diets and exercise. We're going to use fucking thermodynamics.
Your fatass body is a heat engine, designed to keep mammals warm and alive.
Every day you lose heat to maintain that warmth, this burns calories but not enough to lose weight.
Now we have a way to take that little engine to overdrive.
Fill a bathtub with cold water(cold but not too cold), get in for 6 hours and enjoy.
In the time you'll lose calories like extreme full day exercise but without moving a muscle.

This reminds me of the Aristotle conundrum of Achilles racing the tortoise. The tortoise had a head start while Achilles moved twice as fast. By the time Achilles managed to catch up to where the turtle last was, the turtle would be ahead, and so on ad naeuseum. Logically Achilles could never win. Of course, basic math blows this perplexing riddle to pieces, but the idea that one could endlessly prove arguments with circular logic remains true.

The reality of doing what the OP described is that your body will slow down or completely halt other mechanisms (sex drive, among other things)in order to focus on producing heat. This will also slow down your rate of energy consumption from all other vectors while increasing energy consumption in heat management. It would probably end up being a net zero gain or would show a minimal effect at the cost of having to sit in a cold as fuck bathtub for half of your waking day.