Weight loss * Mental wellbeing

Our brains can be fooled to eat less

Our brains can be fooled to eat less Health foods labelled 'light' fail to satisfy

Foods aimed at helping us lose weight are often marketed as "low fat" or "light", but new research suggests that this approach may be misguided.

It seems our feelings of fullness after eating are linked to our belief about how much we have eaten, rather than the actual amount of food on our plate.

Scientists at the University of Bristol carried out a series of experiments to test how peoples' perceptions about how satisfying different foods might be affected their eating habits.

In one test, volunteers were shown pictures of the ingredients of a fruit smoothie. Half were shown a small portion and the other half a much larger portion. Both groups were then asked to rate the "expected satiety" - how full they would feel after eating - both before they ate the smoothie and after. Participants who were shown the large portion of fruit reported significantly greater fullness, even though all participants consumed the same smaller quantity of fruit.

A second test used a rigged bowl of soup which had a hidden pump fitted to it. This allowed the experimenters to increase or decrease the amount of soup in the bowl as the person ate it, without their knowledge. Three hours after the meal, it was the perceived (remembered) amount of soup in the bowl and not the actual amount of soup consumed that predicted post-meal hunger and fullness ratings.

Lead author Jeff Brunstrom commented that "the extent to which a food that can alleviate hunger is not determined solely by its physical size, energy content, and so on. Instead, it is influenced by prior experience with a food, which affects our beliefs and expectations about satiation. This has an immediate effect on the portion sizes that we select and an effect on the hunger that we experience after eating."

These results could have important implications for food labelling. For instance diet and health foods are often labelled as being "light" or "low fat" - phrases which tend to suggest they will not be a satisfying eating experience.

“Labels on 'light' and 'diet' foods might lead us to think we will not be satisfied by such foods, possibly leading us to eat more afterwards” added Dr. Brunstrom. "One way to militate against this, and indeed accentuate potential satiety effects, might be to emphasize the satiating properties of a food using labels such as 'satisfying' or 'hunger relieving'."

The results of the study will be presented at the Annual Meeting of the Society for the Study of Ingestive Behavior (SSIB).

This article was published on Tue 13 July 2010



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