Carrots will not sustain; they have a high glycemic value (according to Mr. South Beach diet) and basically turn to sugar and blast through your system....they will not remotely fill you, but if you need a zap of energy in about 1/2 hour, carrots and orange juice should be quite helpful.
value" refers to. http://www.mendosa.com/gilists.htm lists the
glycemic indices and glycemic loads for carrots from four different
studies, and the glycemic indices (how fast your blood sugar rises
after you eat them) are all over the place, but the glycemic loads
(the product of glycemic index and "available carbohydrates", which
is total carbs less fiber, i.e., the amount of carbs your system
actually absorbs) are all low. I take this to mean that carrots
contain a lot of fiber and a small amount of sugars or things that
your body converts to sugars. Perhaps if your sense of being satiated
depends on getting a lot of carbs, then carrots won't fill you, but
if it depends only on getting something in your stomach, they will.