TIL the faintness sensation come from hyperventilation is a result of respiratory alkalosis, which is caused by reduced CO2 (acidic) level in blood. CO2 is equilibrated with HCO3- (basic) in blood as a pH buffering solution. The lung controls the amount of CO2 whereas the kidney controls the amount of HCO3-. So breathing rate is determined by the level of CO2. Although the CO2 exhaled contributes to the majority of weight loss in human, hyperventilation is not a feasible way to lose weight because the benefit is marginal compared to the downside of respiratory alkalosis. A better way to lose weight is through producing more CO2, which is achieved by increasing metabolism rate.