by Tim Henriques T-Nation
One often-overlooked component in the relentless pursuit of muscle is the importance of nutrient-rich blood. This article intends to give you, the lifter, an understanding of how the body regulates blood nutrients and what hormones are involved in the breakdown and build up of tissue.
Understanding this will help you make better sense of nutrition plans and will help clarify the key relationship between hormone levels and physique improvements.
That said, this article is not meant to be a detailed thesis on the subjects of nutrient breakdown and transport and I don't claim a perfect mastery of the material at that level. However, just because a topic can get pretty deep doesn't mean it isn't worth examining on a more fundamental level.
The Blood Notes
Your blood is constantly circulating in your body (it does about one full circuit every minute at rest) and is carrying vital nutrients to your various cells and tissues. The body likes to keep blood levels reasonably static and has a number of ways of monitoring and controlling this. The two major ways of affecting blood levels are taking something new into the system (i.e., eating food) and breaking down previously stored nutrients.
The eating food part is straightforward. You eat food, which consists of carbohydrates, proteins, and fats. The food is then broken down through digestion into various building blocks – glucose for carbohydrates, amino acids for protein, and fatty acids for fats. The body then absorbs these building blocks from the bloodstream. Most of this happens in the stomach (secondarily) and the small intestine (primarily).
Once your blood levels are normalized, any excess nutrients are then stored for future use. The body stores glucose as glycogen, a complex carbohydrate, in the liver and the muscles. A normal person has about 300-500 grams of glycogen in their body – about 100 grams are in the liver and the rest spread throughout the muscles.
Amino acids are stored as protein. An important note is that they're not just stored inside protein (and thus not functional), but they're stored as muscle. This muscle can then help you move, lift, and impress the ladies.
Fatty acids are stored as body fat, otherwise known as adipose tissue. While fat can only be stored as fat, it's worth noting that excess carbs and protein can also be stored as fat.
This process of storing and building up is considered to be anabolic and the key hormone regulating the storage of all nutrients is insulin.
If the body needs nutrients and none are consumed from food, it will begin to break down its storage supply to keep blood levels normal. This process of breaking down the tissues is considered to be catabolic.
All key storage forms can be broken down back into their original form – glycogen into glucose, protein to amino acids, and adipose tissue to fatty acids – and these building blocks can now be used for energy.
There are two key catabolic hormones associated with this process. Glucagon is released to break down glycogen into glucose. Glucagon also is responsible for the breakdown of adipose tissue into fatty acids. However, it's not responsible for breaking down protein.
(Tim H. prediction: Glucagon will become a drug of choice for bodybuilding in the future since it breaks down fat but not protein.)
Cortisol is the hormone that breaks down protein into amino acids and then converts them into glucose, which can be used for high intensity energy. The key signal for the body to release cortisol is when glycogen levels are low and glucose is needed for energy – think running 10 miles at a good clip while on a restrictive diet.
Cortisol can also be released when one is under high levels of chronic stress (think overtraining or being in a bad situation such as divorce, terminal illness, etc.).
Here's a picture that tries to capture what's taking place:
There are some key things to point out. First, I like to think of the process of storage and breakdown as either one-way streets or two-way streets.
A two-way street is when the process can be reversed. Glucose can be stored as glycogen and then glycogen can later be broken down into glucose – this is a two-way street. Each nutrient and its basic storage form function like that.
A one-way street is when that physiological process happens in just one direction. For example, excess protein can be stored as fat, but fat can't be broken down into amino acids. Protein can be broken down and turned into glucose, but glucose can't be turned into amino acids.
Key Hormone Summary
What follows is a simplistic and short summary of some (not all) of the important hormones in the body. To reiterate, the endocrine system is very complex – included here are a few interesting tidbits for people engaged in serious fitness training.
Anabolic (tissue building) hormones
Testosterone – released from the sex organs, Testosterone directly affects skeletal muscle by telling it to grow larger and stronger, releases GH, and directly affects motor nerves by improving their efficiency, thus increasing neuromuscular coordination.
Growth Hormone – released from the pituitary gland, GH increases protein and connective tissue synthesis, breaks down fat, and boosts the immune system.
Insulin – released from the pancreas, insulin serves as the shuttle to take the building blocks of the macronutrients out of the blood and store them, thus lowering the blood levels of those nutrients.
Catabolic (tissue breakdown) hormones
Cortisol – released from the adrenal glands, cortisol breaks down muscle tissue to be used as fuel in the form of glucose. It can also break down glycogen and adipose tissue, suppress the immune system, and may suppress bone formation.
Catecholamines – more commonly referred to adrenaline, catecholamines are also released from the adrenal glands. They break down all nutrients to increase the blood levels (so more fuel is available for work), increase the heart rate and blood pressure, decrease reaction time, and increase force production.
These hormones are very useful to the fitness enthusiast but one can't constantly release adrenaline without consequences. Compared to the other two catabolic hormones listed, catecholamines would be reserved for "special" fight or flight responses.
Glucagon – released from the pancreas, glucagon helps break down glycogen into glucose and fat into fatty acids.
Why Do We Need to Know This?
Knowing this information helps you make a plan to achieve your goals. If you want to lose weight then obviously you can't continuously fill up the blood pool with food coming in – you have to restrict that part of the equation (control calories) at some level.
Some foods can be converted into other forms easier than other foods. For example, simple processed carbs can be converted to fat easier than more complex, natural carbs.
There are times when you want to raise your blood sugar and thus get a bit of an insulin spike, for example immediately after a workout. Knowing this can help you see the value of peri- and post- workout nutrition/supplementation.
I see gym members all the time working out on the treadmill, most assuredly with the goal of losing weight, while sipping on a Gatorade. This knowledge helps you realize that while drinking a carbohydrate-containing sports drink certainly might aid performance, drinking one with the goal of aiding in weight loss is not the ideal path to follow.
If building muscle is your goal, this information can help you realize that the body wants blood levels to be stable, and thus in most circumstances reasonably frequent meals that prevent catabolism and promote anabolism are necessary.
To avoid getting fat in the process, those foods need to consist of good quality protein and fats with some carbs, but without over doing the total food and carbohydrate consumption.
Finally, intermittent fasters take note, this info can also help you understand why intense exercise when fasted is both tough to do and likely not ideal for the serious lifter.
If glycogen levels are depleted, the body still needs its high intensity energy – fat alone isn't enough to fuel a killer workout as it's a long lasting but weak fuel. It will then release cortisol to meets its needs, likely resulting in the loss of muscle.
So the athlete is breaking down their muscle to fuel their workout, which is supposed to build their muscle – see the problem?
The bottom line is that understanding this information helps make nutrition make more sense, and in these days of conflicting data and experts arguing over the minutia, anything that makes sense sounds good to me.