[SpicyLemonZest]

https://www.bmj.com/content/349/bmj.g7257 is one analysis of oxygen/CO2 exchange being a major component of weight loss. As the authors say, it's really a question of chemistry; the CO2 you metabolize from your fat has to go somewhere.

To be clear, I think your instinctive reaction is correct. It would be extremely silly for someone to read this analysis and conclude that they'll lose weight if they learn some special breathing technique to maximize CO2 output. The point is that "calories in - calories out" as a diet strategy is the same kind of error.

[dekhn]

By the way, if you ever want to start a scientific argument, bring up this paper among doctors and scientists. It never fails to start a big argument that is usually concluded with "human metabolism does not violate the conservation of mass/energy" (many doctors and scientists believe that "burning fat" with oxygen causes you to lose weight directly).