Effects of energy density and portion size on development of acquired flavour liking and learned satiety.

The concept of learned satiety (LS) suggests that associations between the sensory quality and post-ingestive effects of foods may lead to acquired control of meal-size. Although a recent study appeared to support LS since participants learned to eat more of a flavoured cereal with lower energy density (ED) after repeated experience, suggesting that they adjusted voluntary intake to ensure adequate energy was consumed, the large serving portion used in training may have lead to over-satiation. To investigate this further, groups of 12 men were assigned to one of four conditions based on the trained serving portion (150 or 300 g) and presence or absence of cues to differentiate high and low ED versions. In the absence of sensory cues, neither mass consumed nor rated pleasantness differed between high and low ED conditions either before or after training, resulting in greater energy intake in the high ED condition. When sensory cues differentiated ED, intake increased significantly post-training in both the high ED condition trained with the small portion and low ED condition trained with the large portion, and flavour pleasantness changed similarly. Moreover hunger increased significantly after the food was tasted in both conditions where intake increased. These data provide further evidence that learning can moderate meal-size dependent on energy content, but suggest that these changes are driven by changes in flavour liking rather than LS.