insulin and building

The Role of Insulin in Building Muscle (and Bodybuilding)

Insulin is a hormone recognized most widely for its role in regulating blood glucose (or blood sugar) levels in the body. When glucose levels rise after eating, the pancreas releases insulin in order to drive glucose into the liver, muscles, and fat cells.

Generally, high insulin levels cause a decrease in muscle and fat breakdown and a corresponding increase in muscle building and fat storage. This is why insulin is classified as an anabolic hormone. As a result, the role insulin in muscle hypertrophy and growth has been a topic of interest for the past few decades.

This article will explore two controlled uses of insulin: (1) timing meals in order to manipulate the release of natural insulin and (2) injecting supplemental insulin.

Maximizing Insulin Response

In order to maximize your body’s natural insulin response, eating before and after strength training is critical. Eating before your workout not only fuels your body for the task ahead, but also releases insulin, which will decrease catabolism (destructive metabolism) and prevent muscle breakdown.

After your training, eating within 30 minutes will replace muscle glycogen (carbohydrate stores) and promote muscle repair and growth of tissue damaged during exercise. Both meals/snacks should contain at least 2-3 servings of carbohydrates AND protein, such as Greek yogurt with granola or a turkey sandwich.

Protein shakes and bars can also be good options when whole food is not a convenient option. Training on an empty stomach can leave you feeling weak and easily fatigued during your workout, and skipping your post-workout meal will result in decreased muscle synthesis and increased soreness.

Even for the amateur strength trainer, nutrient timing can help maximize the body’s natural insulin response and keep you in an anabolic state.

While planning your meals around your workouts is a proven strategy for decreasing muscle breakdown and increasing muscle repair, some competitive bodybuilders take the process a step further, injecting supplemental insulin to further promote muscle anabolism. In order to gain a better, more practical understanding of the role insulin plays in muscle hypertrophy, I reached out to Steve Spaulding, a national level bodybuilder based in Columbus, Ohio.

Steve Spaulding’s Take

Steve has over 15 years of experience as a bodybuilder and personal trainer, and offers coaching services through his business SS Fitness. Steve pointed out that injecting insulin to promote hypertrophy can be extremely risky and should only be considered under the supervision of a doctor or a coach with verified experience.[1]

According to Steve, Humalog is the most common source of insulin used by bodybuilders, “at a dose of 4-6 units for basic users.” If you are going to take insulin as part of your strategy, it is absolutely essential that you also consume the right amount of carbohydrates at the correct times in order to keep your blood glucose from dropping to dangerously low levels.

Steve noted that most users consume 10g of carbohydrates per unit of insulin immediately after injecting. Steve also stated that more advanced users may take much higher doses of insulin, and while it can contribute to increased anabolism and improve the quality of muscle gained, in most cases the risk simply does not outweigh the reward of using this hormone.

According to a study published in 2015 in the Journal of European Endocrinology, taking a normal therapeutic dose of insulin (similar to what someone with diabetes would take) does not result in increased muscle growth when amino acids are present in the body. In other words, simply taking a BCAA supplement or drinking a protein shake before your workout can stimulate muscle synthesis such that a normal dose of insulin likely won’t confer any additional benefit.[2]

According to the same study, the amount of insulin necessary to actually trigger increased muscle hypertrophy was approximately 50 units per day–an amount far beyond what our body could ever produce naturally. For reference, a typical therapeutic insulin dose for someone with diabetes would be roughly 10 units of insulin per day.[3] Injecting 50 units of insulin risks hypoglycemia, coma, or even death.

For the average person (and even the average bodybuilder) seeking to gain muscle mass, eating protein and carbohydrates 30 minutes before and after your workout to stimulate muscle growth and repair is the safest course of action.

Steve summed this point up in a concise, no-nonsense way:

The risk far outweighs the reward. If you are a recreational bodybuilder or compete at the local level there is absolutely no reason for you to be using insulin.

Proper nutrient timing and training tailored to your goals is your best bet. Please feel free to leave questions or comments about this topic!

NOVA Sports Nutrition would also like to wish Steve good luck at North Americans in 6 weeks! Follow Steve on Instagram: @bbuildersteve


  1. Spaulding, S. (2017, July 19). E-mail interview.
  2. Trommeln, J., Groen, B., Hamer, H., DeGroot, L.C., & Van Loon L.J. (2015). Mechanims in endocrinology: exogenous insulin does not increase muscle protein synthesis rate when administered systematically: a systematic review. European Journal of Endocrinology, 173(1), R25-34. Retrieved from:
  3. Snyder, C., & Hirsch, I.B. (2014, April 10). Type 2 diabetes and insulin. Retrived from:

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