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.
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 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