Insulin – The Muscle Building Hormone

Insulin is a protein that is secreted from the pancreas when a carbohydrate or protein source is ingested into the body. It is transported in the blood in order to regulate blood glucose levels as they must be closely monitored by the body in order to ensure internal conditions in the body remain stable and constant.

Insulin’s Roles in the Muscle Cell

  • Glucose uptake across the cell membrane
  • Glycogenesis (Glycogen synthesis)
  • Amino acid uptake
  • Protein synthesis
  • Gluconeogenesis (the generation of carbohydrate from non carbohydrate sources – ie inhibiting protein degradation)
  • Glycogenolysis (the breakdown of Glycogen to glucose)


The conclusion of all of that is that insulin plays a huge part in muscle building as it allows for better amino acid uptake resulting in greater levels of protein synthesis. Furthermore, it increases glucose uptake into the cell, which results in fuelling muscular contractions. Does that mean we should look to maximize insulin levels throughout the body and we’ll experience great muscle gains with no negative effects, yes?

Not exactly. Insulin also has an anabolic affect in adipose (fat) tissue and it decreases the rate of lipolysis (fat breakdown) thus decreasing fatty acid plasma levels stopping the body from utilizing fats for energy.


In order to avoid insulin’s anabolic affects in the adipose tissue it’s ideal to be as sensitive to insulin as possible, to allow muscle cells to be able to utilize it effectively to fuel contractions and aid in protein synthesis. The more desensitized the insulin receptors become, the lesser ability the muscle cells have in utilizing the insulin and the more insulin is used in lipid formation and fat storage. The leaner an individual is the more sensitive they will be to insulin and thus, that individual may find it far easier to add muscle, as their insulin will be able to transport glucose and amino acids efficiently. This is where the ‘dirty bulk’ theory is shown to be false as leaner individuals are far more anabolic than individuals who carry a large amount of excess body fat.


Insulin Levels and Post Workout


z274Your body is most sensitive to insulin at particular times throughout the day. One of these is after a resistance training workout, so post-workout is a good time to have a source of carbohydrates and protein to spike insulin levels. Post-workout is when your muscles need nutrients urgently as they’ve just been broken down by your training and your body will be in a very catabolic (breaking down) state. Around 30g of fast digesting carbohydrates post workout with a source of easily digestible protein is sufficient to maximize recovery and protein synthesis. Followed by adequate intake of overall calories throughout the day.



7 Ways to Achieve Greater Insulin Sensitivity


  1. Resistance training
  2. Cardiovascular training
  3. Low carbohydrate/ High fat nutrition
  4. Manipulating carbohydrate levels over time e.g. Carbohydrate cycling
  5. Eat plenty of Omega 3 fatty acids (found in oily fish and nuts)
  6. Control blood glucose levels by avoiding massive insulin spikes caused by eating large amounts of fast digesting carbohydrates. Complex carbohydrates with sources of protein and fats affect blood glucose levels less, alongside high levels of total daily fibre.
  7. Regular consumption of cinnamon in the diet and supplementing with ALA (alpha lipoic acid) has been linked with increased sensitivity (ALA can be found in the diet in foods such as broccoli, spinach and tomatoes but in smaller amounts than in supplements).


Justin Bland
University of Leeds
BSc (hons) Sport and Exercise Sciences with Physiology
Read More