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The Anabolic Window & Your Hormones

Nutrient Timing Revisited

Posted by jmboiardi - June 26th, 2015

What is the “Anabolic Window”?

There seems to be some confusion about what the "anabolic window" is and its importance post-workout as well as the role of various hormones when it comes to building muscle and losing body fat.   The term “Anabolic Window” is a bit nebulous as everyone is different and has their own metabolic idiosyncrasies. The main concept is that post workout is when your body's demands for glucose and protein are at their highest as muscle fibers have been damaged and glucose has been expended. To optimize growth, it is best to replenish these stores within 60 minutes of working out - hence the term "anabolic window". However, the body is very receptive to these nutrients even 2 hours or more post workout. Some people say it is OK to miss this window and just make up the nutrient and calorie deficit with your next meal.  I personally do not recommend missing post workout meals on a regular basis as doing so will be like taking one step forward and one step back. If you occasionally miss a post workout meal, eating some additional calories at your next feeding will do more good than harm but won't be as effective as post workout as your body will not be as receptive for nutrients.

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Glucose and Glycogen – What is the Difference?

Glucose and Glycogen are intertwined. Glucose is the preferred fuel source by all body tissues. It is the form of sugar present in the blood after your internal body processes have digested the sugars (of all types) you eat. Monosaccharides, Disaccharides, and Polysaccharides are the various sugars in all food. Glucose is the simplest and easiest form for the body to use as fuel.

Glycogen is a storage medium for glucose usedby the liver and skeletal muscles. Think of them as local containers of glucose to be used for additional energy demands when needed. Glucose is like gasoline and glycogen is like a gas tank. Muscles use this extensively as they are within muscle tissue locally and the liver releases glucose from its glycogen stores when the body's glucose levels are low or there is increased demand for glucose - especially for the brain which consumes about 120 grams/day of the glucose produced in the body from carbs. This is also why sometimes after a big carbohydrate meal your muscles look bigger and fuller and why bodybuilders carbo-load two days prior to a contest after months of carb restriction.

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The Role of Hormones

There are 4 primary hormones to be concerned with when trying to build muscle and lose body fat: Insulin, Growth Hormone, Cortisol, and Testosterone.  

Insulin is one of the most powerful and anabolic hormones in the body. There is a delicate balance between Growth Hormone and Insulin in bodybuilding that you can naturally manipulate via food, eating windows, and exercise or manipulate via drugs. Insulin's main job is to force nutrients into your cells - glucose, protein, fats - and signal your fat cells to store excess glucose and calories as body fat. This is why it is sometimes called the "fat storing hormone." It is produced in the Pancreas. Type 1 diabetes is when specialized cells in the pancreas don't produce enough insulin.Type 2 diabetes is when you continually eat foods full of processed and simple sugars and your pancreaspumps out so much insulin to reduce the rush of glucose caused by these simple sugars that your body cells "ignore" insulin and become resistant. This is dangerous as glucose is TOXIC to the human body in high dosages and is the main cause of Metabolic Syndrome in America. This is why diabetics die of insulin shock, lose limbs and their eyesight as high glucose destroys their vascular system, and are at high risk for heart disease and cancer. This is why fat and cholesterol have never caused heart disease contrary to the mis-information we have been fed for decades. Carbohydrates of all forms stimulate insulin release. Protein has a minor impact and fats have no impact at all. This is why you need to watch the amount, types, and timing of eating carbs when you are trying to get real lean and for optimal health.

Cortisol is your "fight or flight" hormone produced in the Adrenal glands on top of your kidneys.  It can facilitate gluconeogenesis, which is when the body can convert protein and fats to glucose in times of starvation.  Gluconeogenesis is one example of why the body can live without carbs but can’t live without protein and fat. However, the body will switch to burning fat before it cannibalizes protein.  Only in severe starvation situations is protein cannibalized.  Cortisol forces all your blood to your periphery like your muscles (thus inhibiting digestion of food), makes you more alert, and reduces testosterone levels - the body is preparing to fight or flee and thus can't be bogged down with trying to digest food and build muscle.  Cortisol is catabolic – meaning it is not designed to build muscle or stimulate your metabolism but rather prepare the body to run or fight.  Stress induces a Cortisol response.  Too much stress makes the body think it is in constant danger which leads to too much Cortisol being released which counteracts your efforts in trying to build muscle and lose body fat.   Working out too long or too intensely too often will increase Cortisol secretion.  Cortisone, the most powerful catabolic steroid and anti-inflammatory available, is derived thru enzymatic action by peripheral tissues on Cortisol.

Growth Hormone is produced in the Pituitary gland in your brain.  Its primary role is the growth and repair of bodily tissues.  It also is the key hormone to unlock all types of fat stores to release their fatty acids to be used as energy when glucose is low or not present.  Insulin and Growth Hormone are antagonistic which means when one is present the other is not and visa versa.  Hence, Insulin tends to be predominate in the day and Growth Hormone at night when you sleep.  Here is where an eating protocol like Intermittent Fasting (IF) comes into play.  By eating only wholesome carbohydrates with a low glycemic index (Insulin impact) during a set “feeding window” of usually 8 hours you restrict Insulin release to a set time frame.  When you fat the rest of the day and thru the night – usually 16 hours – Growth Hormone is released.  After 12 hours of fasting, Growth Hormone levels can spike as much as 2000% naturally.  Since the body has no glucose for fuel yet still has demands for energy (especially the brain), guess where the fuel comes from?  The answer is your body fat.  With the typical American diet of simple processed sugars and long eating windows, the body is constantly in a state of Insulin release which not only leads to fat storage but also limits the time Growth Hormone is active to burn body fat.

Testosterone is the primary male sex hormone produced in the Testes from direct signaling by the Pituitary gland in the brain.   We all know the importance of this hormone for building muscle.  It is the primary anabolic hormone for males and the primary sex drive hormone for both men and women – though men produce 100s of times more Testosterone than women.  High blood glucose reduces serum testosterone levels which is why Metabolic Syndrome leads to “man boobs” and high body fat as well as erectile dysfunction.

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All these hormones work as part of a delicately balanced and closed-loop feedback system called the Endocrine System.  Food, environment, stress, and other external factors all have impact on this system and how it performs.  Weightlifting and a nutritious diet have the most positive effect for both body transformation and health.  This is why I am not a fan of IIFYM or “cheat meals”.  The effects on metabolism and the endocrine system are real and over time produce deleterious effects on health and body composition – regardless of your age.

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What about eating some peanuts and raisins after working out?

Scott_Herman  Edit  Delete  Close

It's a start, but in my opinion defintiely not enough food.  What are your daily macros?  Have you used my calculator on the @mealplan page?


Nice article! I fast until 45 mins before I train, I get some carbs in me and eat post workout. Occasionally I have to train in the morning which means I do miss that post workout window, its only once a week though if that.

Scott_Herman  Edit  Delete  Close

just keep some sweet potatoes on standby! haha


Great artice @jmboiardi, I am sure you opened the eyes of many "bros" today with this!


I have no thyroid - lost it to cancer. I've been on levothroxine for a good while now. How much fun (how much harder) will it be for me to build muscle?

jmboiardi  Edit  Delete  Close


Sorry to hear that.  The Thyroid is indirectly involved with muscle building as it controls metabolism and body heat.  It does not directly impact testosterone, growth hormone, or insulin levels.  However, if your thyroid is sluggish and you experience hypothyroidism you will have a hard time burning carbs and fats and will have low energy which will affect your workouts.  If your doctor is consistently measuring your Thyroxin medication levels and testing your TH hormone levels and they are in the normal range for someone of your age, you should have no harder time building muscle than someone who still has their Thyroid gland.


Thanks for taking the time to put this article together John. Much appreciated!


Getting that food in post workout is super important. Sure, it doesn't have to be the minute you drop that last weight, but getting a shake in about 30 minutes after working out, and a meal another 30-60 minutes later is what I try to do.

And it's important to know how those hormones work, given how much of an impact they will have on your gains.

Great article @jmboiardi!


Thats an ideal article


It is extremely important to replenish your storages after burning through them after a workout! You definitely do not want to fast for TOO long after a workout!

jmboiardi  Edit  Delete  Close

Agreed.   I cap it at no more than 90 minutes after a workout.  Immediately afterwards is ideal but some people can't make that window and worry too much that their workout was all for not if they can't refuel within 60 minutes.  90 minutes is a safe threshold.


Great article @jmboiardi !
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another awesome article @jmboiardi