Insulin

Insulin is an anabolic hormone that is secreted by the pancreas in response to glucose, amino acids, and hormones. Insulin promotes protein, fat, and glycogen synthesis, and inhibits catabolic processes.

Glycemic Index

Different foods yield different blood glucose responses. The glycemic index is an indicator of a food's impact on raising blood glucose levels. A food's index is determined by comparing the blood glucose response of the food to that of white bread or glucose. The higher the glycemic index, the greater the food's impact on increasing blood glucose levels.

Foods with simple carbohydrates or starches that are easily hydrolyzed by the digestive tract generally have high glycemic indices. However, there are individual responses to different foods,and it is important to note that most foods are eaten in combination with others, as in a meal.

Fiber, especially soluble fiber, and fat can slow the absorption of carbohydrates from the digestive tract, blunting the glycemic effect of a food.

Serotonin

Serotonin is a brain chemical that promotes a sense of well being. Some common anti-depressants act by increasing serotonin availability in the brain. A side effect of these drugs is a decrease in appetite.

Insulin promotes amino acid entry into the body’s cells, but tryptophan is partially protected from this effect because it is the only amino acid loosely bound to albumin. An insulin spike after a carbohydrate load results in an increase in the tryptophan to large neutral amino acid ratio in the blood, and a resultant decrease in competition for trypotphan entry into the brain via the amino acid carrier at the blood brain barrier. Increased tryptophan in the brain could result in increased serotonin production. Therefore, people who crave carbohydrates may be looking for a "serotonin fix". Avoiding the insulin "spikes" by regulating carbohydrate intake would decrease the "dependence" on carbohydrates.

Diet and Water Weight

Individuals consuming a high protein/low carbohydrate diet often experience a dramatic weight loss in the first week. Low carbohydrate diets result in a loss of glycogen stores and a concomitant water loss. One gram of glygogen "holds" four grams of water; the average adult has glycogen stores of 400 grams. In addition, high protein diets promote water loss to rid the body of excess nitrogenous wastes. Some of the high protein diets are ketogenic, and ketosis is also dehydrating. The water weight lost is regained with the return to a higher carbohydrate intake.