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 “rewarding” and, for the same reason, often end up overeating on these foods. This “wisdom” is so obvious that it has rarely been challenged in rigorous studies – that is, until now.
In a paper just published in OBESITY, 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.
Thursday, November 5, 2009
Has anybody done this study with 28 obese people? Are their results different?
Thursday, November 5, 2009
I’m so glad I found your site. I love finding solid intellectual data in easy-to-digest form. Thank you for your work! Keep it up!
Tuesday, November 10, 2009
I’m not so sure I completely agree with the conclussions of this article. I do agree that if a person is quite hungry before they start a meal then the choice of which food and how much it will take to feel satisfied affects the decision. But, in my mind, (and experience) taste plays a huge role in the food choice and the level of fullness is at times a distant second to the brains desire for more of that taste. If someone is not really hungry and the temptation of an addictive food is offerred, say two large chocolate-chip cookies versus an orange I know the choice is too often the wrong one.
Wednesday, November 11, 2009
To people researching choice of “tasty” vs “fill-up” food:
Try testing (testing, not asking) the SAME people after bringing them to different levels of hunger.
Day 1: Have test subjects over for lecture and chat on some irrelevant topic. Serve meal on time, with a wide variety of food to choose from. Note what they eat.
Day 2: Have tests subjects go to gym and put in a full round of exercise. Serve meal late (Make sure you haven’t a diabetic or someone else for whom getting really hungry would be dangerous) Offer same food choices, note what people eat.
Do people eat differently as regards “tasty food” vs “food to fill you up” when they have different levels of hunger?
I wonder about this because I have a teenage son who is an athlete and he craves what he calls “hearty” food – which is traditional food my mother made in the 50’s. Meat or fish, potatoes, and 2 or 3 vegetables. Apple pie for dessert. (but if he’s hungry and there’s only apple pie ready right now he’s not happy – he wants dinner first, “real food”)
If he’s not training he’s not hungry – at least not ravenous – and he’s quite happy to snack on pie or cookies.
(His only weight problem is keeping it on)