There is only one trick I am aware of, eat less while doing more stuff. The oxygen idea is pretty bad. See https://en.wikipedia.org/wiki/Oxygen_toxicity https:

There is only one trick I am aware of, eat less while doing more stuff. The oxygen idea is pretty bad. See https://en.wikipedia.org/wiki/Oxygen_toxicity https://en.wikipedia.org/wiki/Oxygen_toxicity The oxygen thing works the other way around hypoxic environments increase metabolic rate for a small number of days. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4091035/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4091035/