A recent study, as reported in the Globe and Mail today, provides some confirmation of what many rowers have long felt - protein in a diet suppresses appetite better than fats or carbohydrates. In fact, the researchers were looking at the hormone ghrelin , secreted by the stomach, which is an appetite stimulant. Drinks containing more protein did a better job of suppressing ghrelin than fats, and while carbohydrates initially did a good job, later on they were quite poor. This of course will be familiar with anyone who is quickly satisfied by a high carb feed, only to be extremely hungry shortly thereafter.
This obviously bears some resemblance to the effect seen in high glycemic index foods, where insulin reacts to high blood sugar after high carbohydrate foods, often overreacting and actually lowering blood sugar.