The Ultimate Laymen's Guide to Understanding Glucose, Blood Sugar and Insulin

Nov 29, 2012
Blood sugar blood glucose

I've heard from people more than once that they tried paleo and it just didn't work for them. I'm always intrigued by this and I always ask the person about what happened. Where do they think the Paleo Lifestyle let them down?

Usually the problem revolves around weight loss and not seeing enough pounds drop off in a quick enough fashion. The strange thing about this is, that in 9 out of 10 cases the person will sing the praises of the paleo diet by saying how much better they felt mentally and physically. They say that they had more energy and focus yet they quit trying to "be" paleo and are now back to their normal SAD routine. (SAD = Standard American Diet)

AHHHH! This frustrates me on a couple of levels. The first thing is that if you feel better and you have more energy then you're probably on the right track. Secondly, I think there's a real problem with a frame of mind that thinks we deserve good health and fitness despite what we eat or how we exercise.

Listen to me, just eat healthy all the time. It's your health for goodness sake! You are not entitled to good health and fitness. You have to earn it and take care of it. Your body will work with you to maintain optimal health if you take care of it with good food and exercise. It doesn't mean you have to always pass up on a piece of cake but your default choice should be the healthy one.

The Secret of Glucose is in the Chemistry

There's a whole body of science called biochemistry. If you want to lose weight, lose fat, gain muscle and enjoy an overall healthy lifestyle, it pays to know a little biochemistry. Do you have to be a scientist that works in a lab and writes reports? Absolutely not.

If you're interested in how your body uses food to either be used for energy or stored as fat then please read on. I'm a simple guy so we'll skip a majority of the biochemistry lingo and talk in terms that everyone can understand.

And trust me... when it comes to keeping fit, healthy and lean you need to have a basic knowledge of how glucose (a.k.a. Blood Sugar) works and how insulin works. People with diabetes have to understand this process or they will die. Most people without diabetes have very little understanding of this process but we're going to fix that starting now.

One last thing... glucose and blood sugar are the same thing. So don't get confused if you see that I use one or the other in different spots throughout the post. I tried to stay consistent and on target with my usage.

One of the key systems in the body is how we get energy from food. While the process of converting glucose into energy is a beautifully designed system, and very complex, as human beings we have figured out how to ruin it with standard diets that are high in grains, processed carbohydrates and sugary beverages.

What was once a system designed to help us maintain our health has turned against us and in some instances even tries to kill us by triggering diseases like type 2 diabetes and heart disease.

Understanding glucose and the role it plays in the body and where it comes from can significantly increase your ability to lose weight, gain energy and live a healthier life. But most of us are not taught this stuff in school. And even people who do learn about this stuff in school have conflicting points of view on what a healthy diet really is.

But I'm here to set the record straight. In the most simple way possible I want to help you understand what glucose is, where it comes from, what it's role is in the body and how it can either be your friend or be your foe in the game of health, fitness and being lean.

What is glucose?

Very simply, glucose is sugar. It's a carbohydrate that all the cells and organs of your body use as a primary source of energy. It's important and it's necessary. The brain uses glucose as its primary source of energy and the availability of glucose influences psychological processes.

Some studies of shown that acts of self-control actually reduce blood glucose and predict poor performance in subsequent self-control tasks. Here are some of the self-control behaviors that improve when a sufficient amount of glucose is available: controlling attention, regulating emotions, quitting smoking, coping with stress, resisting impulsivity, and refraining from criminal and aggressive behavior.

It seems like not having your glucose in check could cause problems with sticking to a healthy, paleo lifestyle... would you agree?

At this point you should understand that glucose is essential. If your blood sugar runs too low it's dangerous to your health and if it runs too high it's dangerous to your health. You need to find a happy medium. But don't worry that you have to track your blood glucose at all times. Your body is an efficient machine when it's taken care of. It has the whole process taken care of without you having to really do anything. Isn't that great?

Where does glucose come from?

From the foods you eat! When you eat your body will convert the food into glucose and store the glucose into your muscles and liver as glycogen. Pretty much every food you eat can and will be converted into glucose and used for energy by your brain, tissues and cells.  If you eat protein and carbohydrate then they will be converted into glucose at some level and will be stored in the muscles and liver as glycogen.

The level in which food impacts the glucose levels in your body is what the glycemic index and glycemic load information are for. It's fairly common knowledge that eating foods with a higher glycemic index and/or a high glycemic load will have a greater affect on increasing the level of glucose in your blood stream. Foods that are higher in carbohydrates and higher in sugar will have a greater impact on increasing blood glucose levels and, therefore, will be higher on the glycemic index and potentially have a higher glycemic load.

Glycemic Index vs Glycemic Load

The glycemic index compares the impact a food has on blood glucose levels to that of pure glucose. Usually white bread is used as the control and it has a glycemic index of 100. So any food that falls on the glycemic index at 70 and above is considered high and will increase blood glucose levels considerably after eating them. If a food has a glycemic index of less than 55 then it is considered low and will not significantly increase blood glucose levels.

Glycemic load actually takes into consideration the serving size of a given food in conjunction with the glycemic index to give you a better understanding of how a food will affect blood sugar. How much you eat of a particular food will have a significant impact on how it affects your blood sugar. For example, watermelon has relatively high glycemic index at 76 but it's glycemic load is relatively low at 4.

Another way to think about glycemic load is eating candy like Skittles. If you were to eat just one Skittle the impact of that one Skittle on your blood sugar would be insignificant. However, if you actually ate a whole serving of Skittles your body would see a significant increase in blood glucose.

Glycemic load gives you the impact in real terms by using the serving size in the equation. This is why glycemic load is a better gauge of the overall affect a food has on your blood sugar. A glycemic load of less than 10 is considered low and anything over 20 is considered high.

What purpose does glucose serve and why is it important?

We've already talked about the important role of glucose providing energy to your brain, cells and muscles. On a more functional level you need to supply your body with enough glucose so you can complete basic physical and mental tasks. You also need glucose so you have enough energy to engage in various forms of exercise and sports. If you're eating a healthy diet of real food your body will ensure you have enough glycogen to give to your muscles and brain to function at a basic level. However, when we introduce intense exercise or athletics, things change a bit.

Glucose and Exercise

All exercise and athletic performance are not created equal in the depletion of glycogen and the need to replenish glycogen stores after the activity, exercise or athletic event.

Two factors come into play when looking at the impact exercise or physical activity has on glycogen levels and the need for glycogen replenishment. Those two factors are the intensity of the activity (low or high) and the duration of the activity (short or long).

A very high intensity activity such as an all out sprint uses carbohydrate at a very high rate but the total use of muscle glycogen is limited due to the brief duration of the sprint. A single 30-second sprint will reduce muscle glycogen approximately 25-35% of the total glycogen stores in the active muscles. If you were to continue to do multiple sprints you would deplete your muscle glycogen even further. In fact, after just two 30-second sprints glycogen levels could drop by as much as 47% and after three such sprints muscle glycogen drops to zero. This is part of the reason why sprinting is usually done in short bursts and not for long periods of time. A good example of this would be HIIT or High Intensity Interval Training.

Blood Glucose and Resistance Training Such as CrossFit

The same factors can be applied to resistance training like weight lifting. The intensity, duration and overall amount of work done in a workout session will determine how much muscle glycogen is depleted.

If you're doing CrossFit then you are most likely involved in high intensity resistance training. Compound movements that utilize a lot of muscle are at the center of CrossFit workouts and usually these exercises are programmed in a circuit manner meaning that you will complete any given set of exercises back-to-back without rest (A1, A2, A3). This style of resistance training would deplete muscle glycogen at a significant level.

The bottom line is that muscle glycogen is depleted the most by high-intensity exercise that utilizes a lot of strength, speed and force. Steady state cardio does not tap into the fast-twitch muscle fibers that store a majority of muscle glycogen. Therefore, if all you do is lazily jog on a treadmill for 45 minutes then you probably don't need to refuel with a bunch of carbohydrates after you workout.

After an intense workout, such as a grueling CrossFit session, you have a short window of time to get the maximum amount of replenishment from a post workout meal. The optimal amount of time to consume your post workout meal is less than 30 minutes and no more than 60 minutes following your workout.

If you haven't read The Paleo Diet for Athletes I suggest you pick up a copy and check it out for more information on fueling yourself post workout with a Paleo Diet. Just beware that The Paleo Diet for Athletes is geared more towards endurance athletes and if you aren't a a marathon runner you may need to tweak the dietary recommendations to fit your needs.

What role does insulin play in all of this?

I'm glad you asked. You'll hear people talking about insulin levels all the time but very few people actually understand how this process works. Which is a shame because it can be the difference maker in whether you achieve your fitness, health and body composition goals.

As I mentioned above you'll want to get a post workout meal in your system as quickly as possible after a high-intensity workout. Why is this? In short the answer is because your body is craving nutrients to replenish and rebuild broken down tissue and refill glycogen reserves. You've depleted your glycogen stores so your body needs more glucose to be stored as glycogen in the muscles to be used for future workouts.

Insulin is released by the pancreas after you eat a meal and it is responsible for ensuring glucose gets to the appropriate cells. Insulin is also responsible for making sure your blood glucose levels are not too high because high blood sugar levels are toxic to the body. Insulin will either direct glucose to your muscles or liver. Once those two places are full with all the glucose they can convert to glycogen your insulin will start giving the glucose to your fat cells causing you to gain more body fat.

After a high-intensity workout where you depleted your muscle glycogen your body will be extremely sensitive to insulin. Meaning the insulin will work quickly to transport and store glucose in the muscles and liver. Since your muscles are depleted of glycogen they will be like thirsty sponges craving the insulin to bring them the glucose and nutrients so it can be converted into glycogen and be ready for the next intense training session. Your body is extremely sensitive to this insulin response for the first 30-60 minutes after your training so that is why it's recommended that you have a post workout meal within that time period.

How can glucose and insulin work against you?

There really aren't any negatives when your glucose and insulin system are operating as they're supposed to. The problems start happening when things get out of whack on a systematic level.

The main culprit is consuming too many foods that are high glycemic which provide the body with more glucose than it can use or store. The body can only store glucose as glycogen in two places, your muscles and your liver. Once those two places are full, and they do have a limit, your body has to take the glucose and convert it to fat. And guess what? Your body has unlimited fat cells so you continue to get fatter and fatter the more glucose (aka Sugar) you consume.

Doug McGuff, M.D., the author of Body by Science, states it very simple in his book:

"At the point that your glycogen stores become completely full, glucose cannot be rammed down the path of glycogen synthesis anymore. Therefore, its only metabolic destiny is now to be metabolized as fat." 

And guess what? Your body has unlimited capability of converting glucose into fat so you continue to get fatter and fatter the more glucose (aka Sugar) you consume above and beyond your body's requirements.

This is also how someone becomes insulin resistant. Since your blood sugar levels are at elevated levels all the time due to the foods you're eating your insulin levels are also elevated. This means that insulin is constantly trying to get your blood sugar levels to normal. After a period of years your cells will become insulin resistant, meaning that they don't respond to insulin's message of storing the glucose that is in the blood stream.

Once your insulin resistant you dramatically increase your risks of getting type 2 diabetes, kidney disease, blindness, nerve disease, neuropathy and heart disease. Your body simply isn't operating like it's supposed to and it starts to turn against you.

How do you make your blood sugar work for you instead of against you?

First, understand that it's a matter of balance. You don't want your blood sugar to be too low and you definitely don't want it to be too high. The best way for you to find this balance is with an appropriate eating plan. The Paleo Lifestyle will help you get your blood sugar levels to normal and it will help you maintain that perfect balance for the rest of your life.

Remember, the Paleo Diet is not low carb. It just focuses on healthier carbohydrate sources such as vegetables, some tubers and some fruit. For most of us that have jobs at a desk and computer your body simply doesn't need a lot of glucose because it already has enough glycogen stored up for when you need it. So during the day you'll be just fine if you get a majority of your carbohydrates from vegetables and protein. It will be enough, trust me. After an intense workout you may want to replenish your glycogen stores with some tubers such as potatoes.

You in no way need to be downing a donut every morning or do you need to down a candy bar every day at your 2 o'clock break or stuff your face with pasta for dinner. Your body will have no choice but to store all that glucose as body fat.

If you follow Mark Sisson at all you probably know about the Carbohydrate Curve. This is what worked for me and I know it will work for others because it's backed by science and how the body actually works. If you have a lot of excess fat to lose then you need to make sure you keep your carbohydrates at a low level throughout the day.

Eat all the green veggies and protein you want but stay away from bread, cereal, pasta and other processed carbohydrates. Those are blood sugar bombs that will keep you from dropping fat and will send your blood sugar into the danger zone. If foods like this make up the majority of your diet and you lead a relatively sedentary lifestyle you are asking for insulin resistance and the health problems that come along with it.

If you feel like you're at a good weight and you're working out intensely then your post workout meal is the time where you want to get your carbohydrates from your tubers. If you eat potatoes or rice this would be the time to do it. Not at 8 pm after you sat on your butt all day at the office and now you're sitting on your butt at home in front of the TV. Only after you busted your ass in the gym should you have those starchy carbohydrates and even then you don't need to go crazy.

I think that Diane Sanfilippo summed it up nicely in her book Practical Paleo (you should own a copy) when she said:

"Maintaining even blood sugar levels by only eating good carbs in the appropriate amount for your activity level is the key to not only satiety, but also mental clarity, positive moods, fat loss, hormonal balance, and managing inflammation. Whether your goal is fat loss or health, regulating your blood sugar is absolutely necessary."

I couldn't agree more Diane!

Here are the resources I used for this post:

PubMed: The physiology of willpower: linking blood glucose to self-control.

PubMed: Self-control relies on glucose as a limited energy source: willpower is more than a metaphor.

PubMed: Muscle glycogen resynthesis after short term, high intensity exercise and resistance exercise.

A general overview of the major metabolic pathways.

Revised International Table of Glycemic Index and Glycemic Load Values - 2008

Effects of ingesting protein with various forms of carbohydrate following resistance-exercise on substrate availability and markers of anabolism, catabolism, and immunity.

Skeletal Muscle Glucose Uptake During Exercise: How is it Regulated?

Why you got fat. Fat Head the Movie (YouTube Video)

Practical Paleo by Diane Sanfilippo

Body by Science by Doug McGuff and John Little

The Primal Blueprint by Mark Sisson

In conclusion I want to hear from you and find out if this article helped clarify the process of how blood sugar and insulin works in the body. Please don't be afraid to ask for clarification or tell me if I missed something. This is an important topic for all of us and I think it will probably merit a few follow-up posts.

Also, after you leave a comment make sure to share the post on Facebook so other people can learn and enjoy the post.

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