This idea of a study conduct in the U.S. where smoothies provided two groups of people: some were told it was low in calories (140) and others that was had a lot of calories (620). The fact is that they all took the same milkshake 380 calories.
The researchers measured levels of ghrelin before and after eating. The ghrelin is a hormone released by the stomach when hungry. Ghrelin levels rise half an hour before eating, and returns to normal after eating.
The result was quite interesting; apparently the people who thought it was a high-calorie milkshake had lower levels of the hunger hormone, as if the body was affected by what you know the brain … while people who thought it a shake to lose weight reported higher levels.
What comes to demonstrate this simple study is that the package can significantly affect our consumption; we can eat more of a food that the information provided by the package we think is healthier when it really is not.