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IGF1 and Muscular Development

February 9, 2011 by  
Filed under Hormones, Muscle Building, Recent Posts

By Mike Westerdal author of Lean Hybrid Muscle RELOADED


When growth hormone travels from the pituitary gland to the liver it stimulates the production of insulin-like growth factors (IGFs), which are polypeptide protein hormones. Though there are a number of varieties, among the various IGFs, IGF1 is of the most interest to weightlifters due to its capacity to stimulate anabolic, muscle-building effects. It is comprised of 70 different inter-connected amino acids and is produced when growth hormone levels in the bloodstream rise, increasing the production of binding proteins. IGF1 is known to be the mediator of growth hormone anabolic effects. As such, the interconnected relationship between IGF1 and growth hormone is frequently referred to as the Growth Hormone/IGF1 Axis.

The growth of skeletal muscle cells (hypertrophy) is largely regulated by at least three identified processes:

1) satellite cell activity
2) gene transcription
3) protein translation

Evidence indicates that IGF1 can positively influence each of these mechanisms. Research has shown that an increase of IGF1 in the bloodstreams spurs growth and regeneration by the body’s cells—particularly among skeletal muscle cells, where it is shown to positively impact muscle strength, size and efficiency. Specifically, it contributes to skeletal muscle growth (hypertrophy) by provoking the synthesis of protein while helping to block muscle atrophy.

Other cells that are positively affected by IGF1 include cartilage, liver, kidney, skin tissue, lung, nerve and bone. IGF1 deficiencies can result in stunted growth as well as a host of other related health problems. There are also indications that because it is capable of activating insulin receptors, IGF1 has the ability to complement and enhance insulin’s effects on muscle development. Because IGF1 levels are so closely tied to growth hormone levels, lower levels of growth hormone in the bloodstream correlate to similar reductions in the production of IGF1. As is the case with growth hormone, IGF1 production peaks during childhood and adolescence and declines as we get older.

We know that the ability of muscle cells to bet bigger and stronger is the result of their unique capacity to continuously adapt to the stress of resistance training with weights. Part of the cells’ capability to accomplish this remarkable feat is attributed to muscle precursor cells that reside in and around skeletal muscle cells. These precursor cells are often referred to as satellite cells. For the most part, satellite cells sit dormant until they are called into duty by hormones such as IGF1.

Once activated by IGF1 the satellite cells divide and their nuclei become genetically similar to those found in skeletal muscle cells. This is a process known as differentiation. Once the satellite cells’ nuclei become similar to those of skeletal muscle cells they become critical to muscle growth and development. This is because skeletal muscle cells must increase their number of nuclei in order to grow larger and repair themselves. The larger the muscle, the more nuclei it requires.

igf-1-3Whenever a muscle grows in response to the stress of resistance training with weights, you will always find a correlating increase in the number of nuclei within the skeletal muscle cells.

But this is not the only way that IGF1 facilitates muscle development, growth and repair. IGF1 also interacts with a number of different stress-activated proteins that assist in the regulation of reactions in the muscle cells that maintenance, repair and growth. When IGF1 binds with these various protein receptors it stimulates a host of biological processes that contribute to and regulate muscle cell growth and development.

There are a number of strategies you can employ to stimulate production of IGF1 in your body. First, because it stimulates a strong hormonal response, resistance training with weights will boost production of IGF1. In particular, it induces its most potent anabolic state in skeletal muscle cells during the intense physical stress generated by heavy weight lifting. This is due in part to the fact that lifting heavy weights stimulates the production of growth hormone, which in turn signals the liver to produce IGF1.

Nutrition also has a very strong effect on the body’s ability to manufacture IGF1. For example, a structured regimen that includes occasional fasting combined with periods of undereating has been shown to have a positive impact on the body’s production of IGF1. Note that carb intake has a significant influence on IGF1 production. Evidence indicates that carb consumption should be minimized to one meal per day or immediately after an exercise session. Overall it is important to maintain sufficient calorie intake and increase consumption of omega-3 fatty acids. Omega 3 not only enhances anabolic actions but it also assists in protecting against insulin resistance.

CLICK HERE to learn more about a step-by-step system for eating the right foods, at the right times, with the best training program for maximum anabolic hormone production.


9 Responses to “IGF1 and Muscular Development”
  1. Javed says:

    Can you please cite evidences where carb consumption should be minimized to one meal per day or immediately after an exercise session. This would be helpful!.

  2. Nate says:

    this is all very interesting but Id really like to know your sources for this article.

  3. Jeremy A. Beidelschies says:

    Do you know how IGF-1 would affect someone who has diabetes type 2????
    By the way nice picture to open the article of my Brother Curt Dennis Jr.

  4. Alex says:

    Carbs only post workout ? are you talking about muscle building or fat loss ?
    How can i get 4000 calories in, just having carbs post workout ?
    Something is not right here..
    I know that GH rises when you are the most catabolic, but overdoing it and expecting to grow doesnt make sense to me. Unless you have refeeding periods you just cant get there, and with only one carb meal a day, you mat get ripped, but very weak..

  5. Mike Westerdal says:

    It’s not a strategy to use every day but I do have a warrior day in my Hybrid Diet which is part of my Lean Hybrid Muscle program and thousands of people have had great results from it. Have you tried it yourself? You’re right it seems counter-intuitive but there’s a ton of research on it. For references check out Brad Pilon’s, Eat Stop Eat and Ori Hofmekler’s, The Warrior Diet.

  6. alex says:

    I completelly agree and see the use of a fasting day, may it be weekly or monthly, in order of digestive system cleansing, recovery and even hormone balance..
    I also agree with having less, deserving or cycling carbs.. i for example just have one carb meal on off days, but the article seems to tells us to only have one carb meal post workout everyday.. that seems good if youre on a fatloss or maintaining diet, not gaining for sure..
    Carbs depend a lot on how much overweight you are, bodytype, etc.. you should have referred that orelse a lot of people might try this and stay lean but get nowhere.. just my 2 cents, keep up the good work !!

  7. BJN says:

    Kiefer goes into a lot of detail in his Carb Backloading book about why carbs only post workout and/or at night.

    A lot of his information can be found on his site:

    I’m not affiliated with him in anyway but for those really interested his book goes into thorough depth about why carbs after a workout and also why at night and what kinds to maximize Insulin response, etc…


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