In this episode, we take a comprehensive look at insulin through the lens of health and body composition. There’s a lot to unpack, so we start with the basics and work through common misconceptions, practical implications, and what the research actually shows.
What Is Insulin?
- Insulin is a hormone produced by the pancreas that plays a key role in regulating blood glucose levels.
- It helps move glucose into cells in the liver, fat, and muscle, where it can be stored as glycogen or fat.
- Insulin also supports protein synthesis and reduces muscle protein breakdown.
- It works alongside hormones like IGF-1, playing a role in muscle growth and repair.
- It is considered an anabolic hormone due to its role in storing glycogen, muscle, and fat.
How Insulin Works
- When blood glucose is high, insulin production increases. When it’s low, insulin decreases and glucagon increases to release glucose into the bloodstream.
- Insulin and glucagon are both always present — it’s the ratio between them that shifts depending on the state of the body (fed vs fasted).
A Brief History of Synthetic Insulin
- 1921: Insulin was first discovered through extraction from a dog pancreas.
- 1922: The first human treatment was conducted using insulin from pigs and cows.
- For decades, animal-derived insulin was used despite some immune reactions.
- 1978: Scientists inserted the human insulin gene into E. coli, enabling large-scale production.
- 1982: Humulin became the first genetically engineered insulin approved for human use — a major advancement in diabetes care.
Why Is Insulin Viewed Negatively?
Despite its essential functions, insulin is often misunderstood. Concerns include:
- It promotes fat storage and reduces fat breakdown.
- It suppresses autophagy, a cellular clean-up process.
- Insulin spikes are thought to lead to energy crashes.
- Chronically high insulin levels are associated with health conditions like type 2 diabetes.
Addressing the Misconceptions
Autophagy
- After eating, autophagy slows due to sufficient energy and nutrients in the body — not just because of insulin.
- Over time, autophagy appears to balance out if total intake is matched.
- Protein and carbs both raise insulin, so trying to avoid insulin spikes via low protein and low carb intake may backfire in the long run.
Energy Crashes
- Insulin-related crashes aren’t typical in most people.
- Reactive hypoglycaemia can happen in some individuals, especially when high GI carbs are consumed on an empty stomach.
- Conditions like MCAS or POTS may make these crashes more common, but it’s not a widespread issue for the general population.
High Insulin and Health Conditions
- High insulin levels can indicate insulin resistance, but insulin itself isn’t the problem — it’s the body’s reduced ability to respond to it.
- In insulin resistance, the body requires more insulin to do the same job, creating a feedback loop.
- This shouldn’t deter people with diabetes from taking insulin, as it’s essential to manage blood glucose levels.
What Causes Insulin Resistance?
- A calorie surplus, particularly body fat gain around organs
- Inactivity, since muscle is the primary site for insulin-stimulated glucose uptake
- Chronic inflammation
- Poor sleep and high stress (via elevated cortisol)
- Genetics also play a role
Insulin and Body Composition
- Insulin alone doesn’t cause fat gain — a calorie surplus is still required.
- In insulin-resistant individuals, a higher percentage of excess calories may be stored as fat.
- However, outside of extreme cases, this has minimal impact on body composition.
- Being insulin resistant doesn’t prevent fat loss — fat loss still occurs in a calorie deficit.
- The idea that being leaner improves muscle-to-fat gain ratios during bulking doesn’t hold up unless body fat is extremely high.
Insulin as a Performance Enhancer in Bodybuilding
- Some bodybuilders use insulin injections with high carb and protein intakes to promote muscle growth.
- The goal is improved nutrient partitioning — driving nutrients into muscle cells while trying to minimise fat gain.
- Risks include hypoglycaemia, potential insulin resistance, and unintended fat gain.
- This shows that insulin can be used to improve body composition in very specific, controlled contexts — which contrasts with mainstream fear around insulin.
Health Risks and Insulin Resistance
- Linked with high blood pressure, cholesterol, atherosclerosis, cognitive decline, certain cancers, and PCOS
- Moderate reductions in carbohydrate intake or glycaemic index may help, particularly in people with or at risk of insulin resistance
- Addressing factors like sleep, stress, micronutrient status, physical activity, and body composition is also important
- Many of the longest-living populations eat high-carbohydrate diets, but maintain excellent insulin sensitivity due to these other factors
Insulin and Appetite
- The carbohydrate-insulin model suggested insulin promotes fat gain and increases hunger.
- However, when calories and protein are matched, fat loss outcomes don’t differ, even with differing insulin levels.
- Claims that insulin spikes drive appetite haven’t held up in research — studies show minimal differences in ad libitum intake between low carb and low fat groups.
- While insulin may play a role in appetite, its practical effect seems limited.
Final Thoughts
- Insulin is a vital hormone that plays many roles beyond just glucose regulation.
- It’s often misunderstood and oversimplified in discussions around fat gain and health.
- Rather than focusing on insulin in isolation, it’s important to consider the broader hormonal environment, lifestyle factors, and context.
- The body’s systems are complex, and many hormones — not just insulin — influence outcomes like fat storage, energy levels, and muscle growth.
It’s impossible to cover everything about insulin in a single episode, but hopefully at least some of this was relevant or interesting.
Relevant Blog Posts
9 Supplements for Insulin Resistance | Ideal Nutrition
Relevant Podcasts
Episode 67 – Should You Cut Before You Bulk? | Ideal Nutrition