Are High GI Foods Bad For Runners?
Some might know them as blood sugar elevating foods, causing diabetes and obesity, while others, in contrast, think they are energy-boosting and useful for sports.
Needless to say, the community is divided when it comes to their effects but are high GI foods bad for runners?
Find out all about high glycaemic index foods, how they can affect your performance, and if they’re safe to consume or should be disregarded as a whole!
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There are certain foods which have a bit of a negative reputation, being associated with blood sugar spikes and crashes, diabetes and obesity.
Others suggest they are fine to eat in moderation and could actually benefit your running performance.
I'm talking about high glycaemic index foods and in this post, I'm going to walk you through this confusing topic, the potential pros and cons so that by the end you'll have a clear understanding of what they are and whether you can have them in your meals.
If you need even more nutritional advice, have a look at this free resource page to get more info on how you can improve your performance through a better diet!
What is glycaemic index and load?
In a nutshell, glycaemic index is the term used to describe how much a food could affect your blood glucose level, more commonly known as your blood sugar level.
Glycaemic load, on the other hand, gives in detail a lot more information on how different kinds of food impacts your blood glucose based on a standard portion.
Some foods can have a high glycaemic index and low glycaemic load, and later on you’ll find out how the former doesn’t indicate the food is inherently bad.
Response to high GI foods
Your blood glucose is something that is tightly controlled by your body, and it wants to keep it in a narrow range. This is usually between 4-7mmols per litre.
When it goes outside this range, your body detects that and starts a cascade of processes that either raise or lower your blood glucose level.
In essence, the glycaemic index is a way of ranking how much food could affect your blood glucose. It has a score of 0-100, with 100 being pure glucose, which serves as a reference point. White bread also scores 100, although this does depend on the exact type.
Here’s a glycaemic index food chart if you’re wondering how other commonly consumed foods rank.
Glucose is a simple sugar and the most abundant carbohydrate in your body. It’s the main carb your body uses for energy, both in normal daily life and during exercise.
This might give you a clue that foods affecting your blood glucose the most are carbohydrate-based foods.
For a food to have a high glycaemic index, it needs to contain glucose in an easily accessible form, which is why pure glucose and white bread are ranked at 100.
Your body needs to spend little effort digesting and absorbing food, meaning that food can affect your blood sugar very quickly and dramatically.
Conversely, when someone consumes a low GI food, it takes longer for the food to be digested and the glucose to be absorbed, leading to a slower and more modest rise in blood glucose.
Problems associated with high GI foods
There are two major concerns with these high GI foods.
1. Rapid rise in blood glucose levels
The first concern with high GI foods for runners and people as a whole is that it causes a sudden spike in your blood glucose level, meaning you have to release lots of insulin to bring it back down again.
Unless you’re a diabetic, the GI index of a food is quite inconsequential in itself; it doesn’t dictate whether a food is good or bad.
It's a normal physiological response for your body to release insulin in response to lots of carbohydrates, and this is perfectly healthy and keeps you safe.
The truth is that there is really no good evidence to show that high GI foods cause obesity, type 2 diabetes or any other issues other than dental issues if you don't rinse your mouth thoroughly or have poor dental hygiene.
Yes, they can contribute to obesity, and that's because high GI foods are generally unsatisfying and lack other nutrients, which could fit into overeating and a calorie surplus, but they are not the direct cause.
This whole insulin thing becomes less relevant as well during exercise, because your body has another pathway called non-insulin meditated glucose uptake, which we’ll explore more later on.
2. Poor nutritional profile
On the most part, this is absolutely true. The reason high Gi foods for runners lack other essential nutrients is because they are chiefly carbohydrates with little fibre and are often processed.
But that doesn't specifically make them bad or unhealthy, it just means that they won't necessarily contribute to the nutrients profile part of your diet. If you were solely eating high GI food this could be a problem, but if the majority of your diet is full of fresh, healthy, unprocessed foods, then this really isn't an issue, and that’s why overall context is way more important.
By the way, I have a free nutrition crash course that covers the basic fundamentals to help you train and race better. Sign up in just a few clicks and check it out to learn how to easily improve your nutrition!
Benefits of High GI Foods
Now you know a bit more about the glycaemic index of food and a bit more context to understand that it's not as simple as saying high GI foods are bad; it's more about the overall profile of your diet.
Let’s now discuss how they might be helpful. They can be fantastic for 3 areas: before, during, and after running.
High GI foods before running
I had a client who used to get unpleasant tummy symptoms when running. I dug into their diet and noticed that they frequently had a wholemeal bagel with full-fat cream cheese before running. Now, there's not anything specifically wrong with this, but I suspected it might be the cause of their issues.
Tummy troubles are a common problem for runners. Bloating, abdominal cramps, and even diarrhea can occur, and poor nutrition choices are often the culprits.
The main reason is that the individual usually has undigested food in their gut, which means it'll bounce around while they run and contribute to all those unpleasant symptoms.
One way to get around this is to focus on high GI foods before running.
Since they're easier to digest and absorb, there are fewer chances that they'll still be present in your gut, causing problems when running.
This would mean choosing white varieties of bread over wholemeal and sticking to simple toppings like jam or honey. Reducing the amount of fibre, fat, and protein can be super helpful in stopping tummy problems when running.
In my clients' case, I suggested a white bagel with low-fat cream cheese, and this simple change fixed their nasty symptoms.
High GI foods during a run
If we look at the glycaemic index scale again and go back to glucose, it’s ranked at 100 and serves as the reference point.
If you’re against high GI foods, then consuming something which is pure glucose would be bad or unhealthy, but this just isn’t the case during exercise.
In fact, consuming pure glucose during exercise is amazing because your body doesn’t need to break it down and doesn’t have to process extra ingredients like fat, fibre, or protein.
This is why having high GI foods while running is brilliant: You give your body the energy it needs while dramatically reducing the risk of developing unpleasant tummy symptoms.
How to consume high GI foods during a run
Sports nutrition products like gels, chews or bars, carbohydrate-based drinks are all great examples of this, and can be the perfect form of supplements to have before or during running sessions.
They’re way more beneficial than lower GI foods, because those are just way more likely to provide insufficient energy and also give you bad tummy symptoms.
Earlier, I mentioned non-insulin-mediated glucose uptake, which is a super important counterpoint to the “your pancreas is releasing lots of insulin, and it’s bad for you” view.
During exercise, your body becomes much more receptive to insulin. There’s also a pathway available that means your cells can directly absorb glucose from your blood for energy.
This means that even if you consume significant quantities of simple carbohydrates, like 100g of sugar per hour, for instance, you will produce very little insulin, and that carbohydrate will go to your muscles for energy or help provide extra reserves for your liver glycogen.
Now, most people won’t need or tolerate that amount while running, and my usual recommendation is between 30 and 80g of carbs per hour, depending on whether it’s a short run, long run, or race. However, this is just to highlight a very important point and show how nuanced this subject is.
Use this to your advantage and ensure you properly fuel your next long run!
High GI foods for recovery
Another incredibly helpful area that you can use high GI foods to your advantage is after exercise.
During your hard or particularly long sessions, you’ll have used a significant amount of your carbohydrate stores.
High-GI foods can help replenish glycogen reserves at a quicker rate and can even prove to be one of the best foods for runners. This is because they provide a quicker influx of glucose, which can be converted into glycogen to replenish glycogen reserves.
The current guidance is that 1-1.2g/carbs per kg of body weight after a particularly depleting session is the optimum amount, and recovery shakes, smoothies, and sweets help.
For example, a 70kg runner should consume between 70-84g of carbs if they had had a particularly intense session, which depleted their glycogen reserves.
This is especially important if you have another training session later that day or, for example, you’re doing it in the evening and have another hard session first thing in the morning.
Now, I think it’s important to highlight that I’m not specifically recommending you smash a load of simple carbs after every training session, because that’s unnecessary.
After easy, short sessions, such as low-intensity sessions lasting less than 90 minutes, simply having a normal, balanced meal with carbohydrates within 45 minutes of finishing your session is all you need.
But as I mentioned, if your training volume is particularly high or you need to recover particularly quickly, this could be a great strategy for you.
The bottom line
While high GI foods for runners might seem bad or unhealthy, there’s really way more nuance to it than that.
Foods are not inherently good or bad, it’s just the context in which you use them, and using high GI foods in or around exercise can be a fantastic strategy.
Here’s a video that details the whole high-GI foods debate to give you even more insight into what it’s all about.
