Dr's Casebook: Are you really as hungry as you think?

Dr Keith Souter writes: A study from Sheffield Hallam University a few years ago found that how filling you think a meal to be, can affect how much you eat later. In other words, it affects the amount of hunger you experience.

They did this in a neat way by giving 26 people an omelette for breakfast on two different mornings. On one day they were told they were having a two-egg omelette and on the other day a four-egg omelette. In reality, on both days they received a three-egg omelette.

They were then allowed a pasta lunch four hours later. This allowed the researchers to easily measure how many calories they ate at lunch. They also measured their levels of ghrelin, the hunger hormone.

They found that when people ate what they thought was a smaller, two-egg-omelette they felt hungrier at lunch and actually consumed more calories at lunch than they did on the days that they ate the perceived, four-egg omelette. Their ghrelin levels, however, remained the same on both days.

This shows that the person’s expectation of how hungry they would feel had a definite effect. The ghrelin response was the same, so it shows that they were not experiencing an actual physiological increase in hunger.

Significantly, when they measured the amount of food consumed over the rest of the days, they still found that the total intake was greater when the people thought they had the smaller breakfast. This implies that the psychological impact is from the memory of the food that they had eaten.

This suggests that the influence of the mind on how hungry one can feel is quite important. This may be why slimming diets can be so hard, because if you think the food on the plate is not going to make you feel full, it can make you feel hungry, even though your hunger hormone level has not risen.