The origins of this delectable buttery pastry are lost in European history. Croissants titillate our food reward circuits with their extremely high calorie density, concentrated fat and starch, and salt. We enjoy their light texture, which in fact conceals a hefty load of calories. We seem to particularly enjoy foods, such as ice cream, popcorn, and bread, that are calorie-dense but give the illusion of lightness.
Because of their extremely high calorie density and palatability, croissants provide little fullness per calorie consumed. In their landmark paper on the satiety value of common foods, Susanna Holt and colleagues reported that croissants are the least filling of the 38 foods they tested-- far less filling per calorie than even white bread (1).
In other words, because of how they interact with sensors in the mouth, stomach, and small intestine, croissants scarcely provoke the sensation that tells us to stop eating. As a result, we don't stop eating until we've taken in more calories than we need.
At the same time, the effects of croissants on brain reward circuits make us more likely to crave and choose croissants in the future, and more likely to develop a habit of eating them regularly.
There's nothing wrong with treating yourself to a croissant every now and then, but if you're concerned about excess weight it may be best to eat something else.
Image credit: Sundar1 via Wikipedia