A study provides evidence that being overweight makes people tired and sedentary – not the other way around.
“Overweight people often get stigmatised as lazy and lacking discipline. The results suggest that the idea commonly portrayed in the media that people become fat because they are lazy is wrong,” said lead researcher Aaron Blaisdell from University of California, Los Angeles (UCLA).
“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,” he added.
To understand this, life scientists led by Blaisdell placed 32 female rats on one of two diets for six months.
The first, a standard rat’s diet, consisted of relatively unprocessed foods like ground corn and fishmeal.
The ingredients in the second were highly processed, of lower quality and included substantially more sugar – a proxy for a junk food diet.
After just three months, the researchers observed a significant difference in the amount of weight the rats had gained, with the 16 on the junk food diet having become noticeably fatter.
“One diet led to obesity, the other did not,” Blaisdell noted.
The experiments also suggest that fatigue may result from a junk food diet.
As part of the study, the rats were given a task in which they were required to press a lever to receive a food or water reward.
The rats on the junk food diet demonstrated impaired performance, taking substantially longer breaks than the lean rats before returning to the task.
In a 30-minute session, the overweight rats took breaks that were nearly twice as long as the lean ones.
These findings suggest that a pattern of consuming junk food, not just the occasional binge, is responsible for obesity and cognitive impairments, Blaisdell added in the research published in the journal Physiology and Behaviour.