Source: Dr. Stephan Guyenet. Why do we Overeat? A Neurobiological Perspective. 2014.
One factor that contributes to overeating is food variety.
The graph above shows a study where rats were split in 3 groups… one group got regular healthy chow, the second group got one type of junk food, but the third got multiple types of junk food at the same time (20).
As you can see, the rats eating one type of junk food gained more than the ones eating rat chow, but the rats eating multiple types of junk food gained the most… by far.
There is some evidence that this is true in humans as well. When we have more types of foods available, we eat more… and sometimes more than our bodies need (21).