Isegoria

It used to be that if researchers needed obese rats for a study, they would just add fat to normal rodent chow, but it turns out that it takes a long time for rats to become obese on this diet:

A breakthrough occurred one day when a graduate student happened to put a rat onto a bench where another student had left a half-finished bowl of Froot Loops. Rats are usually cautious around new foods, but in this case the rat wandered over and began scarfing down the brightly-colored cereal. The graduate student was inspired to try putting the rats on a diet of “palatable supermarket food”; not only Froot Loops, but foods like Doritos, pork rinds, and wedding cake. Today, researchers call these “cafeteria diets”.

Sure enough, on this diet the rats gained weight at unprecedented speed. All this despite the fact that the high-fat and cafeteria diets have similar nutritional profiles, including very similar fat/kcal percentages, around 45%. In both diets, rats were allowed to eat as much as they wanted. When you give a rat a high-fat diet, it eats the right amount and then stops eating, and maintains a healthy weight. But when you give a rat the cafeteria diet, it just keeps eating, and quickly becomes overweight. Something is making them eat more. “Palatable human food is the most effective way to cause a normal rat to spontaneously overeat and become obese,” says neuroscientist Stephan Guyenet in The Hungry Brain, “and its fattening effect cannot be attributed solely to its fat or sugar content.”

Rodents eating diets that are only high in fat or only high in carbohydrates don’t gain nearly as much weight as rodents eating the cafeteria diet. And this isn’t limited to lab rats. Raccoons and monkeys quickly grow fat on human food as well.

We see a similar pattern of results in humans.

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