Overweight indiivudals can be seen as lazy with lack of motivation, lethargy and decrease in performance. Now, a new study has found that consuming excessive amounts of junk foods can lead to obesity and as a result, make an individual lazy.

According to the journal Physiology and Behavior, researchers used rats to illustrate that a refined low-fat diet high in simple sugars and refined flour induces obesity and also lethargy.

Researchers at the University of California, Los Angeles, based their findings off of a study conducted by UCLA scientist Aaron Blasisdell, who believes that fatigue is the result of eating too much junk food.

The study observed 32 female rats during a six month period. The rats were divided into two diet groups - 16 rats were given standard rat's diet comprising of unprocessed foods ,such as ground corn and fish meal, and the remaining were given a diet of highly processed food with more fat and sugar.

Lead author Aaron Blaisdell, who studies animal cognition at UCLA, analyzed and documented the data, including the difference in weight gain, which was highly visible just after three months. The diets contained approximately the same amount of fat, protein and carbohydrates, but the rats on the junk food diet had become noticeably fatter.

"By three months there was a statistical difference between the two groups, and from there we just saw a steady, progressive, increase in weight in the rats eating the refined diet," Blaisdell said.

After three months researchers gave the rats a task in which they were required to press a lever to receive a food or water reward and results stated that the junk food diet rats showed impaired movements. During a 30-minute session, the obese rats reportedly took longer breaks than the lean rats. This finding suggested that rats experienced fatigue from eating a junk food diet.

After six month, the researchers switched the diet. The obese rats were given a nutritious diet for nine days but researchers found that it did not help reduce the subject's weight or improve their lever responses; rats kept on junk food for nine days did not see a weight gain. Researchers concluded that eating a junk food diet led to obesity and cognitive impairment.

"Overweight people often get stigmatized as lazy and lacking discipline," Blaisdell said. "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. Either the highly processed diet causes fatigue or the diet causes obesity, which causes fatigue."