Click here for the Episode 7: Fundamentals of The Glucose Never Lies Podcast
During the AID series podcast, Louise and I often discussed technical topics. Louise suggested it might be helpful to dedicate an episode to catching everyone up on some fundamental aspects.
First, we’ll explain diabetes in simple terms. Then, we’ll discuss the importance of glucose entering the portal vein, while insulin—at least in type 1 diabetes—is administered into subcutaneous tissue instead of the portal vein. We’ll explore what that means and its implications.
We’ll also break down how activity affects insulin, essentially supercharging it, and explain this process more clearly. Lastly, we’ll examine what happens when you consume a high-fat meal and experience insulin resistance—what’s really going on in the body?
This episode serves as a reference point you can return to whenever you need clarity on these key topics. We’ll include comprehensive show notes with diagrams to help you visualize these concepts.
John Pemberton (04:38.382)
What Is Diabetes?
A doctor once explained it to me as the journey of toast, which is a simple way to understand what happens when we eat carbohydrates.
- You eat toast (a carbohydrate), chew it, swallow, and it travels to your stomach.
- From there, it moves into the small intestine, where glucose is absorbed into a blood vessel called the portal vein.
- The portal vein connects the intestines to the liver, where glucose is processed.
If you don’t have type 1 diabetes, your pancreas sits above the portal vein, sensing the rise in glucose levels. It then releases insulin, which ensures that most of the glucose is either stored in the liver or transported into cells for energy.
Think of insulin as a transporter—it opens the cell door, allowing glucose to move from the blood into the cells. Many people compare it to a key unlocking a door, facilitating glucose entry for energy production. Some glucose remains in the bloodstream to be transported to muscles and fat cells, where insulin helps it enter.
John Pemberton (06:58.786)
Why Does Blood Glucose Rise After Eating, Even With Insulin?
People often say, I counted my carbohydrates correctly, gave the right amount of insulin 15–20 minutes before eating, yet my glucose still spikes. Why?
The key reason is that in people without diabetes, insulin is released directly into the portal vein, storing most of the glucose in the liver immediately. In contrast, when we inject insulin subcutaneously, it enters the outer blood circulation rather than the portal vein. As a result, much of the glucose bypasses the liver and floods the bloodstream, leading to post-meal spikes.
This is particularly noticeable with carbohydrate-heavy meals, like breakfast cereals, since insulin resistance is typically higher in the morning.
John Pemberton (09:20.066)
How Does Activity Supercharge Insulin?
Activity enhances insulin effectiveness in four key ways:
- Faster Absorption – Physical activity increases blood flow to the skin, accelerating insulin uptake from the injection site into the bloodstream.
- Enhanced Delivery – Exercise boosts blood flow to muscles, meaning insulin reaches muscle cells more efficiently.
- Reduced Breakdown – Normally, insulin is broken down by the kidneys. During activity, blood is redirected to muscles, reducing insulin clearance and making it last longer.
- Non-Insulin Mediated Glucose Uptake helps too!
A simple rule of thumb: 15 minutes of movement lowers glucose by ~2 mmol/L (40 mg/dL).
John Pemberton (11:29.590)
Why Do High-Fat Meals Cause Prolonged High Blood Glucose?
High-fat meals slow digestion, delaying glucose absorption. This can initially cause hypoglycemia if insulin is given too early. However, later on, fat metabolites called diacylglycerols accumulate in liver and muscle cells, disrupting insulin signaling and leading to insulin resistance.
Imagine fat molecules as tadpoles. When digested, they break down into diacylglycerols—tadpoles with two tails instead of three. These molecules interfere with insulin function, preventing glucose from entering cells efficiently, causing prolonged high blood glucose.
The solution? Increase insulin doses or engage in activity to help clear these fat metabolites.
John Pemberton (13:46.222)
Key Takeaways
- Insulin acts as a transporter (key), helping glucose move from the blood into cells.
- People with type 1 diabetes lack sufficient insulin in the portal vein, causing post-meal spikes.
- Activity supercharges insulin by improving absorption, delivery, and retention.
- High-fat meals lead to insulin resistance by disrupting insulin signaling at a cellular level.
- Movement after meals (10–15 minutes) can help manage post-meal highs effectively.
Understanding these principles will help clarify many of the strategies we discuss in future episodes. If you grasp why things happen, implementing solutions becomes much easier.