After a While, The Reward isn’t Worth the Effort.
Six months into the study, all rats were trained to push a lever to get a spoonful of sugar water. The number of lever presses to receive the treat was gradually increased, making the work to receive the reward more difficult.
Rats in both groups began to slow as the task got harder, taking breaks between pushing the lever, with some giving up completely. Starting with the same energy level, however, rats in the obese group took more frequent and longer breaks and gave up twice as fast as the rats on the non-processed diet.
Researchers then switched the diets of the two groups. The rats in the original processed-food group didn’t lose weight or show improvement in the lever-pressing task. This observation led to the theory that a diet of processed foods has a direct effect on the chemistry of the brain that isn’t quickly reversed and is manifested through lethargy.
To test the “chicken-and-egg” theory, the scientists changed the sugar water to plain water. In this way, they could see if motivation was linked to just sugar intake. They found that the obese rats on the junk food diet showed less motivation for water even when thirst was induced. All this testing is significant:
“rats are a great animal model for humans because there is so much overlap in the systems that regulate appetite and metabolism.”
What this means for us is that we are now aware of another side effect of a diet with a high processed-food content.
“Impaired Motivation”
Adding insult to injury, in addition to gaining weight, contracting serious disease, becoming depressed, affecting memory and cognition, and feeling all-around crummy, processed foods make us not care about any of that.
“Diet-induced obesity produces a substantial deficit in motivated behavior in rats, independent of dietary fat content. This holds implications for an association between obesity and motivation. Specifically, behavioral traits comorbid with obesity, such as depression and fatigue, may be effects of obesity rather than contributing causes. To the degree that refined foods contribute to obesity, as demonstrated in our study, they may play a significant contributing role to other behavioral and cognitive disorders.”
Healthy Foods You Should Eat.
