In The Fourth Fuel, science writer Travis Christofferson weaves a fascinating narrative of humanities quest to understand how our bodies produce energy-transporting us on a scientific expedition from the past to the present-across early modern Europe to modern laboratories spanning the globe. The reader is taken on a riveting and revelatory journey that follows Nobel Prize-winning scientists from the 19th and 20th centuries as they map the pathways and cycles that comprise human metabolism. The reader is left with a new and lasting appreciation for the silent chemical motion that keeps us alive and healthy. Ultimately, the narrative arrives at a remarkable discovery that rewrites everything we thought we knew about metabolism-with profound therapeutic consequences. Coming back to the present, Christofferson reminds us that Americans are sicker than they have ever been. Heart disease, cancer, dementia, obesity and type 2 diabetes are rapidly becoming the norm. Yet we are presented with a revelation: the realization that we all have a potent, and easy-to-access hybrid metabolism that generates a different fuel-the fourth fuel-that "supercharges" our metabolism in a way that slows aging and by-passes the metabolic dysfunction that leads to the multitude of diseases that plague modern society.