Placing a high value on salt, sugar, and fat is no longer advantageous to our health, but the craving persists because the brain’s reward centers have not changed for approximately fifty thousand years.

In past millennia, human beings had access only to small amounts of fructose. Small amounts are perfectly okay for healthy humans, and fructose was historically available mainly from fiber-rich fruits, which were lower in sugar than they are today.

The mechanisms are a bit complicated, but the bottom line is that even though it is rich in energy, fructose basically tricks our metabolism into thinking that we are depleting energy—and need to take in still more food and store more energy as fat.[*5]