A diet of junk food not only makes rats fat, but also reduces their appetite for novel foods, a preference that normally drives them to seek a balanced diet, reports a study published in the open-access journal Frontiers in Psychology.

The study helps to explain how excessive consumption of junk food can change behavior, weaken self-control and lead to overeating and obesity.

The team of researchers, led by Professor Margaret Morris, Head of Pharmacology from the School of Medical Sciences, UNSW Australia, taught young male rats to associate each of two different sound cues with a particular flavor of sugar water – cherry and grape.

Healthy rats, raised on a healthy diet, stopped responding to cues linked to a flavor in which they have recently overindulged. This inborn mechanism, widespread in animals, protects against overeating and promotes a healthy, balanced diet.

But after 2 weeks on a diet that included daily access to cafeteria foods, including pie, dumplings, cookies, and cake – with 150% more calories – the rats' weight increased by 10% and their behavior changed dramatically. They became indifferent in their food choices and no longer avoided the sound advertising the overfamiliar taste. This indicated that they had lost their natural preference for novelty. The change even lasted for some time after the rats returned to a healthy diet.

plåtmonster skrev:Socker, Fett och Salt så tycker hjärnan mumma! och beodrar dig att genast äta. Brukar sällan vara bra saker.