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Carbohydrates Part 4: The Glycemic Load

Ok, time to finish this mess up because I have something special for next time.  Last time I looked at some of the major issues with the Glycemic Index including the fact that a single meal, typically of a single carbohydrate, was tested after an overnight fast which is really not how people eat in the real world.  People typically eat meals containing other nutrients (protein, fat, fiber) which impact on the GI, there is a second meal effect and, simply, the general approach to determining GI is a little bit contrived in the first place.

I also looked at one of the big assumptions regarding GI which has to do with the insulin response.   Given the impact of blood glucose on insulin release, it was always kind of assumed that insulin was responding similarly.  That is, a higher GI meant a higher insulin response.  But this does not exactly turn out to be true for reasons discussed in that part.… Keep Reading

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Carbohydrates Part 3: Problems with the GI

So after a couple of weeks of nothing, it’s time to continue this series, which will invariably run to 4 parts because that’s just how I do things (tediously and in an overwritten fashion).

As an overview of last time, I described how the Glycemic Index (GI) is measured along with the implications that it had for diabetes treatment, potentially weight loss and for athletes.  The main take home is that, the development of the GI had an impact on diabetes treatment but was a huge hassle to use.

For weight loss, studies were about half and half on whether or not low GI foods (typically higher in protein and fiber) were more filling or not.  So far as athletes, the benefit of high and low GI are context specific while the physique athletes were the ones who really got hung up on the GI based on what would turn out to be an incorrect assumption about insulin dynamics (discussed today).… Keep Reading

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Carbohydrates Part 2: Glycemic Index

Ok, so I’ve clearly been delaying this article which continues from part 1 and talks about the Glycemic Index and I’ll apologize up front if it kind of sucks.  As usual, it wasn’t planned and the best structure flow has kind of eluded me.  So I’m just going to hammer it out and hope for the best.  But it will probably blow overall.

So  two weeks ago I looked semi-briefly at carbohydrate structure and classification and will summarize that even more briefly here.  There are three primary single sugars (glucose, fructose, galactose) which combine with each other to produce double sugars (sucrose, lactose, and maltose).  There is also High-Fructose Corn Syrup (HFCS) which for all practical purposes is identical to sucrose.  I should have also mentioned that glucose is sometimes called dextrose which explains the naming of maltodextrins, longish chains of glucose that are often found in sports and other food products.… Keep Reading

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Carbohydrates Part 1: Classification and Digestion

On my Facebook group, someone mentioned that something about the GI of cooked versus raw carrots was moving through the fitness community (something like that) and that stimulated me to write this article series.  In it I want to ultimately look at the concepts of the Glycemic Index (GI) and Glycemic Load (GL) but today I need to give a quick primer on carbohydrates which I have done before so the next bits will make sense.

Classifying Carbohydrates

How to classify different carbohydrates in the human has been a topic for decades if not the better part of a century (I’m sure it goes back further than this but I’m not sugar historian) and to make this article make sense, I want to blather about the different types of carbohydrates.


Let me start with fiber.  Composed of a variety of different compounds that I will not name but you can look at here if you really want fiber can be roughly divided into two categories. … Keep Reading

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Carbohydrate Loading for Endurance Events – Q&A

Question: Lyle, what does the science say regarding the proper protocol for carbohydrate loading before a goal endurance event like a full marathon? As usual, internet articles are all over the place: some say 2 days, some a week or more, some say keep calories the same but higher carb percentage, some say to jack it up to 5-7 g/lb…Appreciate any advice! PS – if the answer is “it depends”, please pretend the individual is running 50-60 miles per week with a goal of qualifying for Boston.

Answer: Since I’m at a bit of a loss as to what to write about today, I thought I’d get into the mailbag and take what will be a fairly quick and easy one: carbohydrate loading.  As usual, I’ll give too much background instead of getting to the point quickly.

What is Carbohydrate Loading?

The concept of carbohydrate loading is fairly simple.  First and foremost it’s based on the fact that during fairly intense exercise, fat cannot contribute as much to energy production as most would like (folks spent decades trying to improve this but the fact is that near threshold intensities, carbohydrates are the primary fuel source).… Keep Reading