According to a new study from the School of Medical Sciences at Australia’s University of New South Wales, junk food can alter behavior by causing lasting changes in the brain’s reward circuiting, an alteration that triggers obesity.
Although the UNSW study was conducted on rats, the conclusions are likely applicable to humans because all mammals share similarities in the orbitofrontal cortex, which is involved in sensing and evaluating the pleasurable aspects of food. (Notice that we also see more overweight pets these days, too.)
Over time, animals (including humans) have evolved a simple mechanism that protects us from overeating: As we eat a particular food, the pleasure we get from eating it and the desire to eat more diminishes relative to other, uneaten foods. This phenomenon, called “sensory-specific satiety” reinforces the natural inclination to seek out a variety of foods, which promotes a healthy, balanced diet.