Is the Glycemic Index an Effective Tool for Athletes (or Anyone)?

Low glycemic foods? 

A few years ago my aunt revealed some grim news at a family dinner: she had type 2 diabetes. Within her news was a silver lining: after delivering the news, her doctor asked her to follow a low-glycemic diet to control her blood sugar levels.

I consider that a silver lining because, contrary to what many health professionals recommend, many doctors still resort to low-fat diets to control diabetes, when sugar remains the culprit for high blood sugar and insulin levels. By default, a low-fat diet will be higher in sugar. It makes no sense.

Rather than resort to the “eat less/ exercise more” cliché, her doctor told my aunt to focus on lower-sugar foods and recommended Dr. Jennie Brand-Miller’s book The Low GI Diet Revolution, which was an astronomical step in the right direction.

Trouble was, my aunt carried this and several other books around everywhere she went. She consulted charts in restaurants and grocery stores to ensure she only had low-glycemic foods on her plate and cart. She once had the nerve to reprimand me for ordering a sweet potato, which has a glycemic index of – gasp! – 70. And some of her food choices, even though low on the glycemic index, were less-than-optimal.

In short, she became a pain in the ass. Everything became a number, which dissolved every ounce of joy my aunt once experienced with food. 

The glycemic index had overtaken her life.

What the Hell is the Glycemic Index Anyway!?

Simply put, the glycemic index (GI) measures how quickly a food converts to sugar in your body and raises your blood sugar. Higher-glycemic foods create a quick blood sugar spike, whereas lower-glycemic foods create a less dramatic effect on blood sugar.

What the GI doesn’t look at is how much of that food you eat. That’s where the glycemic load (GL) comes in: this more accurate measure looks at quality and quantity. You can get a food’s GL by multiplying the GL times the amount of carbohydrate grams and dividing the total by 100.

Carrots versus pasta provide a classic example about why GL is more accurate than GI. Carrots have a GI of 47, whereas whole-wheat spaghetti clocks in at just 32. From that standpoint, you’re better off eating the spaghetti.

But wait.

You see, that carrot carries far fewer carbs than pasta. The GL accounts for both. So:

Carrots – 47 x 6/ 100 = 2.82

Pasta – 32 x 48/ 100 = 15.36

That’s a big difference, right?

By the way, Google and you’ll find copious GI/ GL food charts. I like this one from Harvard Health Publications that gives you numbers for 100 popular foods. 

Not a math fan or want to constantly consult charts for the lowest-glycemic foods? Me either. The first time I studied glycemic index and load, I thought, There’s gotta be an easier way to determine food quality.

And there is.

Trouble is, the GI and GL refuse to die, and I regularly have clients ask what I think about them. While they have some good qualities, I generally discourage them, and here’s why:

1.     They Can’t Possibly Account for Every Food You Eat. The GI and GL look at foods in isolation. One little problem there: we don’t eat foods in isolation. These measures couldn’t possibly look at every food combination on the planet. Even among individual foods, the GI and GL can’t account for every variation. For instance, a white baked potato has a high-glycemic index of about 76. Thing is, you’re not going to eat a baked potato plain. Nope, you’re going to throw in some butter, maybe a little sour cream, a handful of cheese, and those awful fake bacon bits. The fat load in those toppings will buffer out the potato’s blood sugar spike. In other words, add these ingredients and you alter that food’s GI and GL. Same thing happens with your meals. Sure, that baked potato has a GI of 70, but everything else on my plate – a grilled chicken breast and broccoli – will buffer your sugar load.

2.     They Don’t Look at Nutrient Content or Quality. A sweet potato and graham crackers both have a GI of about 70. The graham crackers actually have a lower GL than a sweet potato (14 versus 22). You see the problems here, right? A sweet potato comes loaded with beta-carotene and other nutrients and fiber. Unlike the heavily processed graham crackers, a sweet potato is a whole food. Nature, not a factory, created it. The GI and GL are like that creepily polite guy hitting on you at the bar who wants to take you home: they have a one-track mind. They simply look at a food’s ability to raise blood sugar. They don’t account for whether you eat a whole food or whether that food is nutrient-rich.

3.     They Don’t Account for Fructose. Fructose is perhaps the most damaging sugar of all: it increases inflammation, stresses out your liver, and converts to fat. You see, your liver is the only organ that can process fructose. When you eat lots of fructose, you put a huge burden on your liver to process it. Now, the GI and GL look at how a food raises your blood sugar. One problem: glucose raises your blood sugar; fructose doesn’t. So a high-fructose food might register low on the GI and GL, incorrectly signifying it’s okay to eat. That especially becomes problematic with processed foods, which often contain high-fructose corn syrup.

4.     They Don’t Account for Metabolic Differences. The GI and GL assume your insulin mechanism works correctly. In other words, you’re an average, healthy adult. But not everyone falls into that convenient category. If you’re a heavy lifter, foods will have an entirely different effect on your blood sugar and how your body handles that sugar load than an overweight, sedentary person. How can the GI and GL account for such biochemical individuality? They can’t.

The GI/ GL for Athletes

You’re looking for the optimal food plan to complement your workouts. Can the GI and GL play a role in developing that plan?

An emphatic maybe, especially if you love tracking and counting.

Let’s say, as a heavy lifter or sprinter, you want to design an eating plan that incorporates the GI and GL. One study found athletes should eat:

•   Low-glycemic carbs 30 – 60 minutes before exercise

•   High-glycemic carbs during exercise

•   High-glycemic carbs for post-exercise meals. “Low [glycemic] foods do not induce adequate muscle glycogen resynthesis compared with high [glycemic] index foods,” researchers concluded.

So there you go, right?

Unfortunately, other studies yield different conclusions. One looked at how seven male athletes performed during high-intensity interval training (HIIT) using either high-glycemic or low-glycemic. (The control group was in a fasted state.)

Both high- and low-glycemic foods three hours before HIIT improved sprint performance. The high-glycemic group had impaired fat breakdown during exercise.

I wanted something definitive, but instead I found this study that concluded despite “the relationship between GI and sporting performance has been a topic of research for more than 15 years, there is no consensus on whether consuming [carbohydrates] of differing GI improves endurance performance.”

In other words, experts have no freaking clue about how athletes can best incorporate the GI and GL into their diets for optimal performances.

I gave up on these potentially useful but faulty measures years ago. Too confusing, and really, who wants to tally up numbers or reference charts. Like my diligent aunt, counting takes the joy out of eating.

A Far Easier Way to Determine Food Quality (No Math Required)

So back to what I promised earlier: I’ve got an easier way to eat. Focus on whole, high-quality, nutrient-dense foods. You already know these: leafy and cruciferous greens, lower-sugar fruits like berries and apples, quality protein sources, and nuts and seeds.

The good news, as an athlete, is that you can incorporate higher-glycemic foods like sweet potatoes and legumes without worry. Hell, you can even throw some dark chocolate into the mix and you’ll probably be fine.

If you’re especially worried, center the higher-glycemic stuff around your workout; otherwise, stick with lower-glycemic foods. And leave the counting for your next Lululemon sale.

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Fitness expert and strength coach Jini Cicero, CSCS, teaches intermediate exercisers how to blast through plateaus to create incredible transformations. Are you ready to take your fitness to a whole new level?  Find out now!  Take Jini's "Are you Ready?" Quiz at www.Jinifit.com. © 2011 Jinifit, Inc.

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