Insulin is perhaps the most talked about hormone in our industry. Many vilify it as the number one cause of obesity. On the other hand, many bodybuilders take it in hopes of it adding ridiculously crazy amounts of muscle onto their physiques. How can we have such wide discrepancies? The answer is that insulin itself has several roles. These include driving glucose into cells (primarily muscle and liver), stimulating the formation of glycogen, increasing the use of carbs as fuel, increases satiety, increasing the formation of fat and decreasing the use of fat as fuel. Given all of these factors, the goal for those looking to optimize their physiques would be to enhance the anabolic effects on muscle, while inhibiting the anabolic effects in fat mass. The general regulator of this process appears to be Insulin Sensitivity. This article will discuss insulin sensitivity and what factors influence it.
What is Insulin
Insulin sensitivity refers to the ability of insulin to “talk” to tissue. We are of course primarily interested in liver and muscle insulin sensitivity. If insulin sensitivity is high in these tissues then you need very little insulin to increase glucose uptake, glycogen storage, and the converting of glucose into rapid useable energy (Gulli et al., 1992). On the other hand, if you are insulin resistant the opposite occurs in that you need a lot of insulin to do the same job! Generally speaking, when insulin is drastically high then the use of fat as fuel is drastically impaired. In addition, insulin drives blood towards muscle giving a full, nutrient-rich, round look.
Genetics & Insulin Sensitivity
As we all know, blood is most definitely thicker than water. Many people think that obesity is the true cause of insulin resistance. However, genetics is certainly an underlying factor for both. The main way to study this is to take two sets of lean individuals. The first set comes from parents who are lean and insulin sensitive, while the second set comes from parents who are both obese and insulin resistant. When you do this, even though the offspring of the insulin-resistant offspring are lean, they still at the cellular level show all the signs of beginning insulin resistance (Gulli et al., 1992; Pratianawatr et al., 2001; Short et al., 2004). The primary reason why they are able to have normal blood glucose levels is that their pancreas is releasing more insulin. However, all hope is not lost because diet may serve as an answer; Mitochondria
A major player in Insulin Sensitivity?
The powerhouse of our cells are mitochondria. These are the organelles that produce the majority of energy in our body’s. The mitochondria help convert both carbohydrates and fats into ATP (energy). In individuals who are insulin resistant, mitochondria do not work properly (Pratipanawatr et al., 2001). When not fully operational, fatty acids cannot be fully broken down in muscle. When this happens the fatty acids build up in the muscle as triglycerides (stored fat), and eventually convert to many harmful byproducts which are toxic to insulin signaling (Pan et al., 1997). Thus, the key to overcoming insulin resistance is to:
A. Increase the amount of mitochondria in tissue
B. Increase the function of the mitochondria
So how do we do this? The answer is that we need to stress the mitochondria by short bouts of energy deprivation in the cell. Secondly, we have to prevent the build up and stagnation of fat in our tissues. This can be manipulated at least three ways. These three ways include diet, exercise, and supplementation.
Diet & Insulin Sensitivity
A famous study by Dr. Bob Wolfe investigated the question as to if a high-fat diet impaired mitochondrial functionality. You see, up to this study high-fat diets had been vilified. In fact, researchers have said high-fat diets cause obesity and insulin resistance. However, when Wolfe and his team infused fat into human subjects blood they found no negative effects on insulin sensitivity. In fact, the only thing that happened was the fats were used as energy. However, when he infused fats and carbs at the same time guess what happened? Fat burning halted and insulin resistance was immediately increased!
Why is this the case you ask? Without getting into too much complexity, fat must be oxidized or used as fuel in the mitochondria. As discussed, if fat is not used, it builds up in the cell. This causes toxic byproducts to be formed, which cause insulin resistance. It turns out that insulin blocks the entry of fats into the mitochondria. It does so by inhibiting the rate-limiting transport enzyme for fat which is called Carnitine palmitoyltransferase I (CPT-1). This impairs mitochondrial function and insulin signaling. Thus, the first way you can improve insulin sensitivity is by manipulating your carbohydrates.
Chronically high carbohydrate overfeeding (>150 % greater than needed) leads to insulin resistance within days. Thus, it is plausible that by training periodically in a low carbohydrate state that you can improve mitochondrial function and optimize insulin sensitivity. In fact, research from Hansen (2005) and Yeo (2008) found that training every other session in a carbohydrate-depleted state increased markers of mitochondrial function and robustly enhanced fat oxidation. Finally, very low carbohydrate ketogenic diets (<30 grams per day) may also drastically improve insulin sensitivity (Volek et al. 2004)!
Training & Supplementation
The final ways to increase insulin sensitivity are training and supplementation. Both of these rely on the same principle; activating the cells fuel gauge. To clarify inside of our cells lies a sensor which can detect low energy levels. In particular, when muscle glycogen is depleted you turn the sensor on. This sensor is called AMPK. It’s called this because our main energy source in our body is ATP. When ATP is depleted you form AMP. AMP activates AMPK which stands AMP-activated protein kinase. AMPK increases fatty acid transport and oxidation (use as fuel) in the mitochondria. It also turns on the pathways which increase mitochondria itself. Training works by depleting energy in the muscle. This, in turn, turns on AMPK.
High-Intensity Interval Training (HIIT) will rapidly deplete the energy in the cell resulting in an increase in AMPK. As you use up your cells energy through HIIT, AMPK will rise causing an increase in insulin sensitivity. Another way is to perform giant sets. Giant sets as we know are a form of training where we target one muscle group, but we do so in a circuit. Not the basic circuit training you would find at your local gym’s group fitness classes though. To perform a giant set you would choose a muscle such as quads, then perform 3-5 movements at a higher intensity for 3 to 4 rounds at 8-10 reps with 2-4 minutes between each giant set.
We know that giants sets are a great way to increase metabolic rate and improve insulin sensitivity by decreasing the energy in a cell and increasing AMPK. Lastly, low intensity, steady state cardio will deplete energy in the cell and increase AMPK. Furthermore, supplements such as Cinnamon (Cassia or Ceylon) and Berberine at a dose of 6g/day and 0.5g three times/day, respectively, may optimize insulin sensitivity.
Key Take Away Points from Article
1. Insulin is a hormone which increases the storage of carbohydrates primarily in liver and muscle and is important for blood flow and the pumps you get in the gym.
2. Insulin also increases fat storage when levels are high.
3. Insulin Sensitivity is the ability of insulin to signal its effects in tissue. If insulin sensitivity is high then you need very little insulin to drive glucose into tissue after you eat. If its low, meaning you are resistant then you will have high insulin levels, greater body fat stores, and impaired blood flow.
4. Impaired function and number of mitochondria due to a build up of intramuscular fat seem to trigger insulin resistance.
5. Not combining a high carbohydrate diet with high fats can minimize the risk for insulin resistance.
6. Various exercises which deplete muscle glycogen can increase mitochondria and their function and thus improve insulin sensitivity.
1. If you like higher carb diets then we recommend cycling them. On those days we recommend purposely depleting the muscle with exercise.
2. Glycogen depleting exercise such as high intensity cardio is paramount for increasing insulin sensitivity.
3. If you are highly resistant to insulin and both parents are obese or diabetic you might consider a generally low carb lifestyle. Ketogenic dieting for example works very well here.
4. Various insulin sensitizing agents assist in improving insulin sensitivity. These include ketones, cinnamon and berberine.