Study: Junk Food Rewires Your Brain to Make You Lazy

Now you can blame laziness on your diet instead of your personality.

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People tend to believe that weight gain is caused by laziness: We gain weight because we can't be bothered to get off the couch. And when you're packing on the pounds in the depths of your self-imposed wintery reclusiveness, it's not hard to see where that theory comes from.

A new study, however, may turn this popular belief on its head.

Researchers at UCLA have conducted experiments that suggest laziness does not beget weight gain; weight gain begets laziness. More specifically, and a bit surprisingly, junk food begets laziness.

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Aaron Blaisdell hopes his rats will alter perceptions about obesity and laziness.

The study involved preparing two different diets for rats: one low in fat but high in simple sugars and refined flour (essentially, processed junk food), and the other a typical rat diet full of complex carbohydrates. Both diets had roughly the same amount of fat, protein, and total carbohydrates. The researchers then fed the two different diets to two equal-sized groups of rats.

The obese rats took significantly longer breaks between attempting to get the reward, and would give up altogether sooner than the healthy rats.

Over the next several months, the scientists measured weight changes across the two groups and noticed a steady weight increase among the rats fed the “junk food” diet.

"One diet led to obesity, the other didn't," said Aaron Blaisdell, director of the study and professor of psychology at UCLA, in a statement.

But that was simply the beginning of the study. The researchers wanted to observe how the two diets impacted the rats' motivation levels. In other words, they wanted to see if junk food made the rats lazy.

After six months on their respective diets, the rats were individually taught to press a lever to access a spoonful of sugar water. With each successful activation, the scientists made it more difficult to obtain the prize by increasing the number of times the lever had to be pressed.

Both groups grew tired of the task as it became more difficult, but the obese rats took significantly longer breaks between attempts, and would give up on the task sooner than the healthy rats.

Blaisdell told the Los Angeles Times that all the rats "seemed" to have the same energy levels, so it wasn't the weight gain that caused the rats to slow down. Rather, he believes that the junk food diet actually changed the rats' brain chemistry, making them lazy.

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The junk food rat looks with envy upon his healthy cohort. [Credit: Aaron Blaisdell]

This runs contrary to conventional wisdom, which claims laziness causes weight gain—not the other way around.

"Overweight people often get stigmatized as lazy and lacking discipline," Blaisdell said in a press release.

"We interpret our results as suggesting that the idea commonly portrayed in the media that people become fat because they are lazy is wrong. Our data suggest that diet-induced obesity is a cause, rather than an effect, of laziness.”

Hero image: Wikimedia Commons, "AlejandroLinaresGarcia" (CC BY-SA 3.0)

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