It always tickles me when a new scientific study confirms what we already regard as a truism. This time an experiment by Yale University and University of Southern California reveals that when you're hungry, you tend to crave more junk and high-fat foods.
To reach this conclusion, they took normal-weighted and obese individuals and hooked them up to an IV that would regulate their glucose-levels; thus making the brain think they're either hungry or full. Then they stuck them in an MRI machine and flashed pictures of objects, including low-calorie and high-calorie foods.
When the normal-weighted subjects were full, their brains showed more activity in the area that governs logic, reasoning and planning. They did not crave the high-calorie stuff. When they were hungry, the part of their brains that controls motivation, reward and addiction lit up. Junk food, their brain is thinking, is just what the body needs to replenish itself quickly.
A more interesting conclusion is that the brains of the obese individuals responded the same to the junk food whether they were hungry or full. Robert Sherwin, one of the authors of the paper that was published in the Journal of Clinical Investigation says, “In obese people, that executive control is not activated when their blood sugar isn't falling. So they have continued activation of their reward system and that system dominates even if they're not hungry.”