You start with what you eat. There are three (four if you include drinking) main categories: Protein Carbohydrates Fat Your goal is to take reduced carbon (ca

You start with what you eat. There are three (four if you include drinking) main categories: Protein Carbohydrates Fat Your goal is to take reduced carbon (carbon bound to hydrogen) and metabolize it to oxidized carbon (carbon bound to oxygen). That process releases energy your cells can use. The problem with oxidizing carbon is that it creates toxic products ("free" electrons) and involves splitting atmospheric oxygen (O2) into O-, which is very reactive. So then you need a whole host of other pathways to contain that reactive compound. If you really want to understand it, follow the carbon as it comes in, and trace it through to CO2. That's the pathway, and everything else is to support that.