An interesting study in 2004 showed when subjects ate a 12 inch sub sandwich, vs an 8 inch sandwich, their ratings of hunger and fullness were not significantly different.
This has had me thinking quite a bit! Even though the study participants took in more calories with the larger sandwich, they were just as satisfied as those who ate the smaller sandwich. This leads me to believe that hunger and satiety have a strong mental component when it comes to portion control, as well as a physiological component.
The specific study results state:
The portion size of the sandwich significantly influenced lunch intake for both males and females. The majority of individuals consumed the entire 6-inch sandwich. When served the 12-inch sandwich, compared with the 8-inch sandwich, females consumed 12% more energy (74 kcal) and males consumed 23% more energy (186 kcal). Despite these differences, ratings of hunger and fullness were not significantly different after eating the 12-inch and 8-inch sandwiches. (source)
Increasing the portion size of a sandwich increases energy intake (Journal of the Academy of Nutrition and Dietetics, March 2004)
What can we learn from this study
When a food is presented to us in a serving that feels complete , such as a full sandwich, a muffin, or a bowl of cereal, we are satisfied and satiated when we ‘finish the meal’. We eat the full muffin or eat the full sandwich, regardless of the size. When the size difference is subtle, the feelings of being full are very similar.
This makes a lot of sense to me in this example of some muffins I recently purchased. The two muffins were incredibly similar in size. The bakery muffin weighed only 33 grams less than the Costco muffin, and had 80 fewer calories. After eating each one, the level of satiety was rated similarly, yet with the bakery muffin, we saved 80 calories! Over time, 80 calories adds up, so why not be equally satisfied with less food?