March 18, 2012

Insulin, Leptin, And How 'Bulking' Can Limit Building Muscle!

What You Need To Know About Insulin

Insulin is said to be the most anabolic hormone because of its ability to:

·        Activate protein synthesis, glycogen synthesis, and glucose uptake in muscle and fat tissue

·        Inhibit protein degradation, glycogen breakdown, and gluconeogenesis

However, when insulin is present in the blood, it also:

·        Inhibits fat from being burned

·        Activates glycolysis (the burning of carbs for energy)

Insulin is released into the blood in response to carb consumption primarily, and determines whether or not what was consumed will be used for immediate energy, or stored for later usage (in muscle tissue, or the liver as glycogen).

The body is designed to dispose of glucose as it enters the bloodstream because high levels of glucose in the blood is toxic. When muscle tissue or the liver reaches its glycogen storage capacity, the sensitivity of these tissues to insulin decreases to signal that glycogen stores are full, but the remaining glucose in the blood still needs to be disposed of.

When glucose can’t get into muscle tissue or the liver, more insulin is released in attempt to slam it in there, but the excess glucose is ultimately converted to triglyceride, and stored as fat. This becomes problematic because the greater the insulin response, the more resistant the cells become, leading to more fat inevitably being stored over time.

What You Need To Know About Leptin

Leptin is produced and secreted from bodyfat (which is also a hormonal organ), therefore the more bodyfat there is, the more leptin there (potentially) is.


·        Controls metabolism, and regulates hunger.

·        Tells the body to stop producing and secreting insulin after a meal – remember, the greater the insulin response, the more resistant the cells become. Leptin helps prevent this.

·        Increases the burning of fat in muscle tissue, fat tissue, and the liver (to provide energy, and prevent too much fat from being stored).

·        Increases the storage of fat in fat tissue, and the liver (to prevent excess bodyfat loss that may threaten survival or reproductive ability).

·        Is responsible for maintaining optimal thyroid function – when leptin levels are normal, the body will convert T-4 to T-3 (the inactive form of thyroid hormone to the active form). When one becomes leptin-resistant, and attempts to reduce calories to lose weight, the body goes into starvation mode and stops converting T-4 to T-3 to prevent from wasting away.

During/following a meal, leptin is released (from fat cells) to let the body know it is full and to stop eating, while also acutely increasing the metabolism to use the calories that were just consumed for energy to prevent unnecessary bodyfat from being added.

Restricting calories results in the fat cells shrinking initially, as excess fat is used for energy in periods of energy deficit, but soon enough the leptin response during/following a meal is limited, meaning the appetite stays elevated, and the metabolism slows down to decrease energy expenditure and prevent too much bodyfat from being burned.

Why Bulking Is Not An Ideal Way Of Gaining Size

When fat cells become saturated (which is what happens when one eats excessively in an attempt to gain size), more fat cells are created, and since fat cells produce leptin, having more of them naturally results in a greater leptin response than is needed.

When leptin levels are chronically elevated due to increased bodyfat, the message is prevented from getting to the brain to preserve the sensitivity between the brain (hypothalamus) and leptin, meaning the brain doesn’t receive the signal that the body is full after a meal, or that it already has enough bodyfat to survive, so the appetite remains elevated, causing more food to be eaten, and more fat to ultimately be stored. This becomes problematic because the more leptin there is, the more resistant the cells will become to it, leading to less fat being burned, while always feeling hungry.

Once a fat cell is created it is on the body for life (unless it is surgically removed). The body has the ability to add more fat cells (which it does when current fat cells are saturated), but it can’t remove them. Fat cells can shrink by using their fat content as a source of energy, which is what happens when calories are reduced and/or energy expenditure is increased, but the cell itself doesn’t disappear. The more fat cells there are, the easier it is for the body to store fat, and by adding fat cells, the body basically becomes better at storing fat, and worse at getting lean (losing fat).

Overeating increases the leptin set point, meaning a given amount of food that was once satiating, and caused the body to increase its metabolism and start burning fuel for energy, has now increased, and what was once excessive has become the norm. By consuming less than the excessive norm in an attempt to lose weight, the fat cells will shrink initially, but the body believes it’s getting less than is needed, and goes into *survival mode by slowing down the metabolism, while increasing the appetite.

*Cheat meals once or twice a week prevent the body from going into survival mode, which promotes the continued burning of fat.

The Insulin-Leptin Connection

Upon consuming a meal (especially a high carb meal):

·        Insulin is released to shuttle the nutrients

·        Leptin is released to tell you that you are full, speed up the metabolism, and signal that no more insulin is needed (since you’re supposed to be full and not continue eating anyways, there’s no need for anymore insulin to be released).

When the cells are resistant to leptin what happens is:

·        Insulin is still released in response to a meal to shuttle the nutrients

·        Leptin is still released to tell you that you are full, speed up the metabolism, and also to stop sending out insulin, but the message isn’t received, resulting in excess amounts of both insulin and leptin being released, which can result in insulin resistance, leptin resistance, or both – which is possibly the worst thing that could happen, especially if gaining muscle is a priority.

Insulin Resistance + Leptin Resistance = Growth Resistance

Even though a surplus of calories is needed to fuel new growth, after a certain point the excess fatty acids, triglycerides, and glucose become toxic, and sustained nutrient overload can impair the ability to build muscle, as higher levels of bodyfat decrease the ability to synthesize protein.

Insulin resistance results in carbs being stored as fat instead of muscle glycogen, and also the accumulation of triglycerides in muscle tissue, which further contributes to insulin resistance. As muscle insulin sensitivity decreases, so does glucose uptake, meaning less glycogen is stored, and thus muscle fullness is reduced, and the ability to achieve a ‘pump’ during training is limited.

There is a positive correlation between bodyfat and insulin resistance in that the higher the bodyfat, the more resistant the tissues are to insulin and leptin, while the lower the bodyfat, the more sensitive the tissues are to both. As insulin sensitivity is reduced, more fat is gained, more leptin is released, and when leptin levels are high enough for long enough, leptin resistance sets in.

Now You’re Fucked!

The ‘endoplasmic reticulum’ (ER) located inside each cell, is a major site for protein synthesis, and also where the metabolic signals to control glucose, lipid, and protein metabolism are integrated. When the demand to synthesize protein exceeds the cell’s ability to supply it, the ER becomes stressed.

Fat Cells

The ER is very important in regards to fat cells because it is responsible for producing leptin as well, and the larger the cell becomes, the more leptin it produces. If the supply outweighs the demand, and leptin is produced at a greater rate than it is being used, the ER becomes stressed, to which it responds by reducing protein synthesis in attempt to force the body to use the available supply that it’s already created. This is problematic because this process increases inflammation, which is a cause AND effect of stress, thus causing further stress! Nutrient excess is what causes this increased demand for protein synthesis in fat cells to produce leptin, and for proteins needed for triglyceride production and fat storage.

Because synthesizing protein is an energetically expensive process, insulin resistant fat cells can't take up enough glucose to meet the energy demands of protein synthesis, which causes further stress, and the cycle between insulin resistance, leptin resistance, oxidative stress, and inflammation, continues from there.

Muscle Cells

When a fat cell is stressed from nutrient overload, fatty acid uptake slows down, so it gets stored as intramuscular triglyceride instead, since insulin resistant muscle tissue is unable to burn it for energy. This further decreases insulin sensitivity, which causes stress, and inhibits muscle growth because when muscle tissue is stressed, it becomes less responsive to all the triggers for protein synthesis (mechanical tension/loading, anabolic hormones, leucine, etc).

Be Smart!

If bulking is the chosen strategy put on weight, understand that it comes with its fair share of drawbacks, some of which may permanently affect future abilities to get lean. Since insulin resistance can set in, even in trained individuals, in short periods of time, bulking should be limited to periods of a few weeks at a time. When muscle fullness begins to deplete, and the ability to get a pump while training is lost/limited, it’s probably a sign that the bulk has run its course, and continuing down that path with come with negative, and possibly irreversible consequences.

A smarter approach would be to avoid bulking altogether, because the time it can take to get things back to normal may not be worth the hassle in the first place. Not to mention, life will not be all that pleasant when you’re hungry all the time, even when in a caloric deficit.

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