Eating a diet of junk food for just one week was enough to damage a part of the brain that signals overeating, suggests a new research by experts at Macquarie University in Sydney. Researchers found that after seven days on a high fat, high added sugar diet, volunteers in their 20s scored worse on memory tests. The findings suggest that a junk food diet makes it harder for people to regulate their appetite and damage to the 'hippocampus' is a possible cause. The hippocampus normally stops us from binging on more food when we are full by suppressing memories of how tasty it is. The phenomenon has been demonstrated for the first time in humans, say researchers.