When Insulin Is Released
Insulin is released due to a rise in the body's blood sugar level that is induced mainly by your eating carbohydrates and protein. Insulin is primarily responsible for the direction of energy metabolism after eating. Insulin helps regulate blood sugar levels and helps keep them in the proper range.
Insulin binds to specific receptors in cell membranes and diffuses glucose into the cell. Insulin also helps activate glycogen synthase, a process in which glycogen is stored in muscle tissue. In this process, two-thirds of glycogen is stored in muscle tissue while one-third is stored in the liver. Liver glycogen is used primarily to help keep blood sugar levels at a stable level.
Insulin causes glucose transport proteins to increase their activity, which allows for increased glucose uptake by muscle cells. Although insulin helps dispose of blood glucose by storing it as glycogen in muscle tissue and the liver, it can also convert the excess to fat. But then again, insulin can also shut off the fat-burning process. That makes insulin truly a double-edge sword. Many people don't know that insulin causes amino acid uptake into muscle tissue, giving the muscle cells more amino acids to help in the growth-and-recovery process. Insulin promotes protein synthesis via stimulation of the RNA translation process.
Enhancing Glycogen Levals
So you have a hormone that can enhance glycogen levels in the muscle cells, thereby creating a more favorable environment for growth, not to mention causing cell volumization, or swelling. Keep in mind that for every gram of glycogen stored in the muscle cell, three grams of water are stored as well. Insulin's opposing hormone is glucagon, which is activated when blood sugar levels are too low. Glucagon can break down muscle tissue and reduce glycogen stores, so it's important to control it.
So insulin is anabolic in that it allows for a greater absorption of amino acids into muscle tissue but a problem because it can cause fat storage. How do you use insulin to your advantage and minimize its fat-storing effects? The answer is to raise and lower insulin levels at different times in the day. You want to raise insulin levels in the morning and right after a workout - so it's a good idea to take creatine at those two times to maximize absorption.
Spiking Insulin Levels
Spiking insulin levels after a workout by taking in simple carbohydrates and protein - preferably in liquid form - can block the catabolic effects of the hormone cortisol and enable key nutrients to replenish muscle cells. It can also enhance protein breakdown synthesis and lower the breakdown of protein secondary to weight training.
Just are there are times that you want to spike insulin levels to maximize nutrient uptake, there are also times when you want to lower insulin as much as possible to prevent fat storage. One of those key times is at night, before bedtime. Since metabolism is generally lower at night, eating carbohydrates or certain amino acids, like the BCAAs (Branch Chain Amino Acids) - leucine, isoleucine and valine - can cause an insulin response, which may lead to greater fat storage.
It's a good idea to lower your carb intake at night and eat more fiber and protein. Eating fat, fiber or even protein - especially caseinate - along with carbohydrates lowers the rate at which they enter the bloodstream. This tactic reduces insulin levels and may halt fat storage that can result from eating the carbohydrate by itself.
As you can tell, manipulating insulin levels can be hard, but when the desired results are received, your body (and girlfriend) will thank you.
Jalai, R. (2002, October). The Power of Insulin. Ironman, pp. 252-262.