Insulin is an Anabolic Hormone released by the pancreas. It’s primary function is to maintain safe and steady blood glucose levels around 80 to 100mg/dl. When blood glucose rises above 100, insulin is secreted by the pancreas. Then the insulin picks up the extra glucose out of the blood and stores it for future use. There are 3 storage areas for this glucose; muscle glycogen, liver glycogen, or adipose tissue.
The positive side: Insulin builds muscle, it inhibits catabolism of protein, which means the breakdown of muscle, insulin transports amino acids into muscles (BCAA’s). It also helps ensure the storage of glucose in muscle cells, thereby improving performance and recovery.
The negative: Insulin inhibits an enzyme called hormone sensitive lipase, which is responsible for breaking down adipose tissue (belly fat), decreases utilization of fat for energy, instead of burning carbs for energy, so it spares fat (making you fat). Insulin activates lipoprotein lipase, once activated by insulin, it breaks down triglycerides into fatty acids which are quickly converted back into trigylcerides and stored by adipose cells.
If you are looking to gain muscle, you will need a high steady level of insulin throughout the day. If you are strictly trying to lean out, you will want a much lower level throughout the day.
What if you want to gain muscle and loose fat? When blood glucose is is high, insulin is secreted and glucose is stored in muscle glycogen or liver glycogen. When blood glucose is low, insulin secretion is diminished and fat becomes the body’s primary source of fuel. Insulin is like a switch that controls from moment to moment whether you’re burning ft or building muscle. It doesn’t take a whole day for this to change to occur, in fact it can happen in moments. So what that means you can have focused periods of fat burning and muscle building by manipulating your carbs. We now understand that it is optimal to have carbs pre, intra and post workout, because insulin will not convert glucose to fat if it can first store it as glycogen. So after an intense weight training and cardio workout (not a lame ass, sleepy workout) both muscle and liver glycogen are depleted and ready to soak up serious glucose. You will often see bodybuilders during a leaning out phase to have very little carbs through the day, but load up, pre, intra and post, loosing fat and maintaining or even gaining muscle. Another way is to have low carb , and carb loading days. But that is subject for a different day!
So in conclusion, we still need carbs for energy, build and maintain muscle, but how we handle them is what you will see in the mirror.