A few key ingredients can explain a significant amount. Salt, sugar, and fat make American foods taste appealing, while also producing serious health problems.

In Salt Sugar Fat, these three key ingredients are portrayed as the essence of processed foods. Other ingredients are viewed as secondary, whereas the addictive power and negative health effects come from these three key ingredients.

The key ingredients each provide taste, texture, and benefits to cooking and preserving foods. They all complement each other; for example, salt making sugar taste sweeter, and sugar making fat taste better. The author also describes the three ingredients as interchangeable.

The food industry applies engineering techniques to food. It then leverages large marketing budgets. This combination results in precise attacks that consumers can hardly resist.

In Salt Sugar Fat, numerous food scientists discuss the mathematics, psychology, and biology for manipulating consumers to eat more food. The US Army has hired some of these food scientists to engineer its own food.

Next to salt, sugar, and fat, marketing is seen as a fourth key ingredient. Moss treats television advertisements and other messaging as weapons deployed by the food industry to sell its unhealthy products. Through fleets of vehicles in poor neighborhoods, to high-priced celebrity endorsements, the marketing muscle of the food industry is portrayed as a necessary ingredient.