In this chapter, van Tulleken attempts to better understand UPF and its effects on our bodies by looking at what he calls the three “ages of eating” (79). He looks at the means, in these different ages, by which life extracts energy from its environment to grow and procreate. In the first age, bacteria “ate” inorganic materials like iron to make energy. In the second age of eating, an evolutionary shortcut emerged where some animals got their energy from eating other life that had already processed energy. As animals became more complex in this second age, so did their eating requirements. Eating was needed to provide both energy to live and “the elements and molecules that we need to make our bodies” (84).

The evolutionary competition of the second age drove complex systems, like the gut microbiome, to extract the necessary energy and materials from food and to neutralize toxins produced by plants to protect themselves. As a development of this age, processing and cooking gave humans a large evolutionary edge over other predators. It allowed them to kill parasites and extract more energy from food. In 1879, with the invention of saccharin, humans entered the third age of eating.