Originally Posted by Jonny Bones
Are you really saying that fat doesn't need oxygen but muscle does? They both do, that's why very muscled up guys and fat guys all tend to have cardio issues.
No. Fat does need oxygen, but it doesn't require more oxygen when you are fighting like muscle does. Muscle uses oxygen to support energy production in muscle. If you do more work with your muscles, they will require more oxygen to fuel the process.
Fat guys have cardio issues not because their fat is eating up oxygen but because they are typically out of shape. That is, they have low cardiovascular fitness so they aren't supplying their muscles with enough oxygen.