Researchers from Yale University suggest that the mindset place a very important role in how much food you eat at each meal

The researchers gave a 380 calorie milkshake to the participants of the study, saying that the milkshake was either a 620 calorie “indulgent” shake or a 140 calorie “sensible” shake. The researchers found that those who thought they were drinking the high calorie milkshake had low levels of ghrelin hormone which stimulates the hunger pangs compared to those who thought that they were drinking a 140 calorie milkshake.
“This study shows that mindset can affect feelings of physical satiety. The brain was tricked into either feeling full or feeling unsatisfied”, lead researcher Alia Crum said.
Source-Medindia