Hormone called Ghrelin.

So apparently there is a link to what you perceive you eat to how the body processes it.
This was a tremendous story on Morning edition this morning.
Ghrelin is a hormone secreted in the gut. People in the medical profession call it the hunger hormone. When ghrelin levels in the stomach rise, that signals the brain that it's time to seek out food.
"It also slows metabolism," Crum says, "just in case you might not find that food."

I am going to take this one step farther and link it to  the consumption of diet drinks and possibly refute the findings.  People think they are consuming zero calories. And somehow they have no weight gain. So this so called called placebo effect is quite the obvious opposite.

Or maybe the negative publicity of diet soda's have the intended one off placebo effect.

Diet soda's sales have plummeted recently.

There used to be a common perception (mis-perception) that when you consume Thai/Chinese food you would be hungry an hour later. I do not know it always filled me up fine. Probably the perception that people were eating healthy would leave them hungry an hour later.

So in this case Statistics are more like an early season one-piece.