The Glycemic Index, all carbs are not equal
-What’s GI, Joe?
-The Glycemic Index of course
And this was a pathetic pun to introduce the concept of Glycemic Index.
You may have never heard of it, yet it is a really handy and important concept to take into account for you fitness training. Alright, as a personal trainer Tokyo and fitness instructor, one of the basic goal to achieve for me with any new valuable trainee is to make things clear about food. Ain’t no result if your meals are not right. And I don’t mean that a strict diet should be followed, having it right 90% of the time is enough to both get results and eat tasteful yet healthy dishes.
Some so called diet food are sometime pushing the marketing on their “Low GI” nutrition fact.
Macros are for sure important: Carbohydrates, Proteins and Fats are well spread and detailed in a more or less accurate fashion in any serious magazine.
Yet, what’s the difference between 100g of carbs intake coming from Snickers and the same amount coming from plain rice (not taking into account the amount of fat in those chocolate bars)?
The Glycemic Index! Cool! It matches this article’s theme!
So, What is the GI?
The Glycemic Index or GI is the relative speed at which a carb compound is assimilated in the bloodstream compared to glucose.
I other terms Glucose is the gold standard we refer as a GI 100.
If a carbs compound gets assimilated 2 times slower, then its GI is rated at 50.
Carbs are classified into 3 groups:
- Monosaccharide = Simple sugar, such as glucose, galactose found in milk or fructose in fruits. Those are simple and fast to metabolize.
- Disaccharides = Complexes composed of two “sugars”, those are taking a little bit more time to be assimilated, therefore having a lower GI. Sucrose aka table sugar or lactose found in milk.
- Polysaccharides = Those are made of many “sugars” and could be complicated up to the point that our digestive system cannot extract energy out of them. Yet those are good to help digestion such as dietary fibers aka roughage.
How can I know?
Well, you can refer to the list Medical Writer Mendosa established, it’s both exhaustive and accurate.
Mind also something very important: cooking tends to deconstruct complex carbs, this is why fried potatoes have a way higher GI than steam baked potatoes!
What’s the impact on training?
Well, glucose balance in your bloodstream is a finely tuned mechanism – when this one fails to work as intended it is called diabetes – Body needs at all time 20g of bloodborne glucose per hour. Glucose, burnt very quickly as duel for muscles when you train hard!
When it goes too high compared to your training you get a quick rush of energy and then you get worn out really fast. This is due to a hormone called insulin kicking in to reduce the amount of glucose in your bloodstream to prevent damages mainly to your nervous system. And that excess is stored as fat. If we go really deep into the science, insulin is also responsible for a part of the anabolic reaction (muscle grow).
When it goes too low, glucagon kicks in, another hormone that is responsible of the muscle anabolism (destruction) in order to provide energy to your body. While glucagon has other functions we want to limit its effects.
Well, the best is to provide energy that will be diffused at the right pace regarding to your activity within the next 3h for slow carbs or 10-15mins for fast carbs. Except if you are a sprinter, super high GI carbs will almost always result in fat tissues creation.
On the other hand you can easily understand why it is necessary to supplement a reasonable amount of carbs after intense training: to stop the release of glucagon in your bloodstream.