The Role of Insulin in Muscle Gain and Fat Loss By Mike Westerdal of CriticalBench.com
Insulin is an important but often misunderstood hormone. It is perceived as having somewhat of a dual personality in that it is often viewed as being both a 'good guy' and a 'bad guy.' For instance, like IGF1, insulin can have an anabolic, positive impact on muscle growth and development. However, it has also been shown to contribute to an unwanted increase in body fat. This double-edged sword effect is the result of the multiple roles insulin plays in the metabolic system. Mostly due to misunderstanding and an underserved reputation as being a 'schizophrenic' hormone, many people have misconceptions about insulin and the various roles it plays in regulating the body's metabolism.
First of all, insulin is produced in the pancreas and fulfills important functions in regulating the energy and glucose metabolism in the body. In this role it is plays a key role in determining how our bodies make use of the energy obtained from the foods we eat. Consuming foods or beverages with high sugar content stimulates the release of insulin into the bloodstream to manage the spike in sugar. It does this by directing the sugar into the muscle cells and other organs for use as an energy source.
Insulin also plays an important role in regulating the body's cells including their growth and spurs cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle. Glycogen is partially responsible for giving muscles their 'full' appearance but more important, it is the primary fuel source used by the body during resistance training activities. Increasing the storage capacity of glycogen in skeletal muscle cells provides the body with loads of energy during training. In addition, insulin helps to prevent the unnecessary breakdown of muscle proteins, resulting in more muscle being manufactured (anabolic) than is destroyed (catabolic), therefore increasing muscle mass.
As noted, insulin also influences the burning of body fat as a fuel source. However, when insulin levels are continuously high it inhibits the use of body fat as fuel. Lower levels of insulin are associated with enhanced fat burning capacity. Basically, an increase in the use of body fat as a fuel source is inversely correlated to lower levels of insulin in the bloodstream. But keeping insulin levels excessively low for extended periods inhibits muscle growth.
The complexity of insulin's impact on the metabolic system is due in large part to its interrelated relationships with both growth hormone and insulin-like growth factor 1 (IGF1), each of which has a strong anabolic effect in muscle cells. Remember that both insulin itself and IGF1 are viewed as anabolic agents that can inhibit the breakdown of muscle protein while simultaneously promoting DNA synthesis, amino acid uptake and muscle growth.
We already know that many different types of fat and muscle cells require insulin in order to be able to absorb glucose. But sometimes, the body develops a condition known as insulin resistance, which occurs when the muscle cells' insulin receptors become less receptive to the functions of insulin. As a result, not as much insulin enters the muscle cells and other organs, resulting in abnormally high glucose (sugar) levels in the bloodstream. This is known as insulin resistance, which has been shown to be contributing factor in the onset of type 2 diabetes.
As I mentioned, there are a great deal of misconceptions surrounding insulin and its role in muscle building and fat loss. Not surprisingly, these false ideas encourage many guys to take actions that they mistakenly believe will enhance insulin's muscle building and fat burning effects in their bodies. Severely limiting carb intake is one example of a tactic that is falsely believed to positively impact insulin's metabolic roles. They pursue this route in the hopes of minimizing insulin's activity but unfortunately, this strategy does not have the desired effect because it overlooks the important biological functions of insulin.
A better approach to optimizing insulin's role in muscle building and fat loss—while also maximizing the relationship between insulin and IGF1—is through periodic periods of fasting and undereating combined with strenuous exercise followed by post-recovery meals that include both proteins and carbs. The periods of fasting and undereating appear to facilitate an increase in both growth hormone and IFG1 receptors in the muscle cells. When followed up by a post-training meal that includes proteins and carbs, this finalizes the anabolic actions of both the growth hormone and the IGF1. The intake of carbs is essential because growth hormone and IGF1 anabolic actions are only fully activated when insulin levels are increased as they are when one consumes carbs.