Satiety Trumps Reward?Thursday, November 5, 2009
According to conventional wisdom, people tend to go for highly-palatable energy-dense foods because these are more ÔÇ£rewardingÔÇØ and, for the same reason, often end up overeating on these foods. This ÔÇ£wisdomÔÇØ is so obvious that it has rarely been challenged in rigorous studies ÔÇô that is, until now.
In a paper just published in┬áOBESITY, Jeffrey Brunstrom and Peter Rogers from the University of Bristol, tested this seemingly obvious assumption in a series of rigorous experiments – with surprising results.
In these studies, 28 normal-weight participants were asked to rate pictures of 17 commonly consumed foods in terms of palatability, expected satiation and ideal portion size. Importantly, expected levels of reward were assessed based on equicaloric amounts of foods.
Surprisingly, while there was no relationship between the amounts of selected foods and their palatability, reward levels and portion sizes were closely associated with expected satiation. Thus, subjects were likely to select larger portions of energy-dense palatable foods not because they liked these foods more but because they did not trust these foods to fill them up.
In fact, when compared calorie for calorie, subjects considered energy-dense foods as distinctly LESS rewarding than the same caloric amount of less energy-dense foods.
These findings clearly challenge the notion that people tend to select and overeat highly palatable caloric-dense foods simply for hedonic reasons. Rather this data is far more in line with the notion that meal-size selection is largely driven by the expected satiating effect of foods.
Or in other words, the reason that people will eat more calories as French fries than the same number of calories as carrots is because they know that they will need more French fries to get the same sense of fullness.
So even if you don’t prefer French fries over carrots, if you had to self-select the amount of French fries that you think will give you the same level of fullness as a pound of carrots, you will likely widely overshoot your goal in terms of calories.
Perhaps this is why putting caloric content on menus and food labels may be a good thing.