I looked into your O2 theory recently but under the idea of " Is more oxygen better". From what I learned, your blood is 99% saturated at 21% oxygen; so, I don't think that would work. Maybe just try breathing more? Expel twice as much Co2 as you usually do.

But my tips, drink more water, eat less and move more. If you do a combination of these things relative to where you are now, you will lose weight.