The below image is taken from http://www.mendosa.com/satiety.htm and is a compilation of the results obtained in a 1995 study, cited at PubMed (http://www.ncbi.nlm.nih.gov/pubmed/7498104/)

It's Called the Satiety Index

All the foods on the list are rated for satiety level relative to bread being given an arbitrary value of 100%. The higher the percent value on the satiety scale, the more that food satisfies your hunger.

Each subject in the study was given 240 calories of each of the foods on the list over a course of time, trying to rule out as many variables as possible to determine how each of them performed against each other at making them feel satiated (full).

The Boiled Potato Takes the Cake, So to Speak

Of the foods tested in the study, the boiled potato scored the highest for satiety, coming in at 323%. That's to say, eating a 240 calorie amount of a baked potato satisfies one's hunger to the same degree as eating (323/100) * 240 775.2 calories of white bread!

The Croissant is the Biggest Loser

In contrast, the croissant comes in at 47% (less than half the satiety level of white bread). One would have to eat 240 * (100/47) 510.6 calories of croissants to feel equally as full as they would eating just 240 calories of white bread. They'd have to eat 240 * (323/47) 1649.2 calories of croissants to feel about as full as if they'd just eaten 240 calories of a boiled potato! Is that not insane?

Conclusion of the Study

The results show that isoenergetic servings of different foods differ greatly in their satiating capacities. This is relevant to the treatment and prevention of overweight and obesity.

Conclusion Translated into Regular, Everyday English

Focusing one's diet more and more on the high value end of the Satiety Index is very likely to result in less calorie intake and, therefore, healthy weight loss.

Conclusion Translated for the Caveman

Eat more boiled potato. Eat less croissant. Ugh.