The 80's were great.
Terminator, The Breakfast Club, Ferris Bueller’s Day Off, The Goonies, The Princess Bride, Blade Runner, Top Gun, Die Hard, and yours truly all came into existence during that decade.
Clearly this was the greatest decade ever.
You know what else came into existence during that decade? The glycemic index.
Since it was created during this most glorious era it needs two things: Its own song and its own article. I am going to give you both.
Ode to the glycemic index:
Thou were a novel finding in the 1980s
You have sparked some of the most obscene debates on fitness website forums
You have been called the cat’s meow and a burning pile of intellectual garbage
What is the truth about you, you mysterious strange list of numbers?
Cleary I am not a poet, but I am a scientist who studies metabolism and disease for their career.
Over the course of my work, I have been continually intrigued by rather esoteric glycemic index. This very interesting measure that we assign to foods has been adopted quite heavily by two main nutrition circles: diabetes research and bodybuilding.
Over the last decade we have come to learn a lot about this index and what it means for athletes of all types, including lifters.
What is the glycemic index?
The glycemic index is a measure of how much glucose appears in the blood after eating a certain food.
Put simply, it is a numerical value that represents how high your blood sugar goes after you eat a specific food and foods are ranked from high to low. Things like white bread and sugar are considered the “standard” to measure foods against as they have some of the highest glycemic index values.
Here are a few examples of foods and their respective glycemic index values:
- White bread = 95
- Glucose = 100
- Banana = 48
- Chicken = 0
- Eggs = 0
- Cashews = 22
Glucose and building muscle
The glycemic index has been used for decades by bodybuilders and lifters for several reasons as a tool to maximize post workout anabolism, many of them steeped in bro-lore (I use that term with the utmost affection). There are the two main reasons why it was used:
- High blood glucose levels post workout maximize glycogen replenishment and recovery.
- High glycemic index foods spike insulin which is anabolic and shuttles nutrients into muscles.
The first reason is unequivocally true. Consuming carbohydrates post workout and increasing blood levels of glucose increases the rate of glycogen synthesis in the muscles and can aid in recovery.
However, the glycemic index of a food per se is not really an important factor of your carbohydrate source, it is really more about the overall amount consumed. There is no positive data showing that consuming higher glycemic foods post workout results greater gains.
The second reason is both true and false at the same time. It is true that foods that result in higher blood glucose loads result in a greater insulin response and that insulin stimulates nutrient uptake into cells. It is false in that insulin isn’t really anabolic, its main function is more anti-catabolic, in that it reduces muscle protein breakdown.
Additionally, there isn’t any data to support that high glycemic index foods are actually more anabolic and that while it sounds good in theory, the data just doesn’t hold up.
There is a very important aspect of the glycemic index of foods that may be at play in a lot of these “negative” results from above and it has to deal with a VERY interesting study that was done in 2015 showing that the glycemic index is likely a very inaccurate tool for most people.
It varies widely by individual
For decades we have all been told that foods have a specific glycemic index and that we all have a similar response a certain food. Well, it turns out that we have been quite wrong about this idea. There is a wide range of responses to any given food and it isn’t as straight forward as “I always respond high to carbs and you always respond low”.
It appears to really vary by food. For example, in a recent study people given the same exact amount and type of bread had drastically different glucose responses1. One participant had an area under the curve of 15 (meaning virtually no glucose response) while another had an area under the curve of 138 (meaning a large glucose response). There were also values everywhere in between.
The story gets even more interesting from there. If you take two people and give them two foods fairly high on the glycemic index those people can have drastically different responses to each one.
Let us take person A and person B as an example and give them bread and then straight glucose. Person A can have a high response to bread and a low response to straight glucose. Person B can have a low response to bread and a high response to glucose.
What about more complex foods like bananas and cookies? The same story applies, people often have high divergent responses. This has been experimentally proven in hundreds of people1.
It is quite clear that we should probably not use the glycemic index as a very strong tool to predict glucose response by individual. Now that we know that we can ask ourselves a fairly important question as we know that glucose excursion post feeding is important: What could explain this large variance?
From the collective data we have so far it appears that your microbiome (you know, all those lovely bacteria crawling around in your intestines) plays a substantial role in how you respond to the fat, protein, and carbohydrate content of foods 1.
How can you use it?
It is fairly clear at this point that using the glycemic index chart as a basis to determine which carbs are best for you in terms of building muscle and regulating blood sugar is a crude tool at best.
When we couple this with the fact that in almost all research studies done to date, the glycemic index of foods are a poor predictor of recovery and muscle growth when compared to overall available carbohydrate we can make the following conclusions:
- Whether you consume brown rice or maltodextrin post workout, their impact on recovery and muscle growth are largely the same.
- If you are attempting to maximize the last 5-10% of your training and have all your other ducks in a row (training, total calories, sleep, etc.) then doing some self-testing of blood sugar over a few months to determine how you respond to foods might be a decent idea.
The Wrap Up
The Glycemic Index is a largely outdated idea that does not hold up well in individual people.
Furthermore there doesn’t appear to be a meaningful advantage for recovery or muscle growth in virtually all people.
You should spent more time meal prepping and training, and less time worrying about whether the slightly lower glycemic index of brown rice is going to ruin your gains.