There are lots of things in the wide world of the health and fitness industry that are misunderstood.

And GI, otherwise known as glycemic index, is another one you can potentially add to your bag of FIT'N'FLEXED MYTHS. 

As hard as it is to believe, GI is widely taken out of context today by many companies using it as a marketing ploy in the fierce competition for your dollar.

"It's ok, it's low GI" they want you to think, diving into their product with a feeling of wellbeing, coupled with one that you're eating healthy.

There's plenty of talk about normal blood sugar levels and normal glucose in relation to complex carbohydrates, aka "good carbohydrates" - but does it really hold much scientific water?

Before you continue or start only eating low GI foods, let's dive into some of today's scientific data in an attempt to answer the question, is GI important?

THE RESEARCH

Firstly, GI is the number given that measures a food's ability to raise blood sugar, evident in the picture below.

Low GI foods are options like oats, sourdough rye, whilst high GI are foods like donuts and white bread, with glucose (sugar) having a GI of 100 and water a GI score of zero.

WHAT THE MARKETERS DIDN'T TELL YOU ABOUT GI

GI is measured in a FASTED state, with carbohydrates consumed ALONE (1).

This doesn't really translate into the real world at all.

Most people reading this would consume carbohydrates at breakfast along with a protein source.

So why does the protein matter? We'll get to that in a moment.

But even if you're a non-lifter and/or health and fitness is the last thing on your mind, you're almost definetly having milk with, let's say, your breakfast cereal (which is more than likely high GI). 

Milk is largely casein protein (80%) and the rest whey protein.

The point is, that next to no one in a fasted state consumes carbohydrates alone.

WHERE THE PROTEIN AND OTHER FACTORS CHANGE EVERYTHING  

Protein, fat and fibre, all LOWER the glycemic response of a food (1).

So if you wake up in the morning and have an omlette with whole eggs and spinach together with white bread, and are told off by some "expert" as to why the bread should be brown, kindly inform them that the fibre from the spinach and the fat and protein contained in the eggs, all LOWER GI.

But of course, you'll never hear the popular breakfast cereal companies or some of the bread companies tell you this.

The point is, if you like white bread, then eat white bread.

This won't make any difference to your waistline at all, providing you're keeping an eye on your over all calorie intake.

GI AND SATIETY (The feeling of being full) 

Many people might jump up and down at the advice to not stress about high or low GI foods - with the idea that low GI foods will help you feel fuller and high GI foods will lead to more food cravings.

Whilst there might be some anecdotal evidence (which means nothing in the world of science) research pertaining to this claim is NOT concrete and in fact, conflicting.

One study (2) looked at seven "healthy" young men who ingested two of the same diets (46-47% carbohydrates, 41% as fat, and 13-14% as protein).

One group consumed high GI carbs to make up their 46-47%, while the other group consumed low GI carbohydrates to make up the identical percentage.

This study took place over a 30 day period. 

To quote one interesting finding from the paper:

"Initially, blood glucose and plasma insulin concentrations were lower during part of the day with the low GI diet than with the high GI diet, but after 30 days of the diet this difference diminished." 

 

Furthermore, there was no difference in the amount of consumption between both groups. So the high GI group DID NOT receive more cravings which may have led to the consumption of MORE food.

It's findings like these that make the whole GI and satiety claim shakey at best.

Also, GI doesn't correspond with satiety index in any reliable fashion (1).

Take potatoes and white rice for example, which a lot of people dieting make it a habit to avoid.

One study (3) examined the satiety index of certain foods, and believe it or not, it was these foods that ranked as some of highest in preventing hunger!

The croissant was ranked as the worst for satiety, despite being only 3 points higher on the GI scale than white rice! (Just don't tell the French).

So you can see how the GI numbers here don't translate into much.

GI AND WEIGHT LOSS OBESITY & DIABETES

Food companies will also market low GI products in an effort to make you feel like it's better for your waistline.

But the truth is that low GI foods have been found to be no better than high GI foods here (4).

To quote from the above citation: 

"In summary, lowering the glycemic load and glycemic index of weight reduction diets does not provide any added benefit to energy restriction in promoting weight loss ..."

 

The title of another study (5) also strengthens this point.

These authors were pretty clear on their findings when they called their research paper: Should obese patients be counselled to follow a low-glycaemic index diet? No. 

Amazingly, even when it comes to diabetes, one study (6) found that GI wasn't all it'd been cracked up to be. 

To quote from the paper: 

"The proposed protective effect of low-dietary GI and GL (glycemic load) diets on diabetes risk could not be confirmed in this study."

 

Also, many people will have you believe that high GI carbs are more likely to store body fat because of the rapid insulin spike.

Providing you're in a calorie deficit - GI will make ZERO difference to fat gain.

Take for example the professor now dubbed the "Twinkie Professor" - who showed that whilst staying in a calorie deficit and eating nothing but high GI Twinkies - one can lose weight still (7).

He lost just over 12 kgs. 

IT'S NOT JUST CARBOHYDRATES THAT SPIKE INSULIN

Some people opt for the low GI types of carbohydrates or shun them altogether, thinking this will result in NO insulin spike due, as long as only protein and greens are on the menu.

Well this couldn't be further from the truth.

One study examined the insulin response to a fixed amount (239 calories) of different foods over 2 hours, following a 10 hour overnight fast (8). 

Check out this table below:

As you can gather, foods that many think will NOT spike insulin, in fact, do. 

WHEN LOW GI FOODS CAN ACT AS THE HIGH GI TYPE

Many people might look at milk on the GI scale and see it scores about 30.

As it's a low GI food, they might get stuck into it whilst avoiding the high GI option of, for example, white bread.

Well here's an interesting fact for you. When it comes to insulin response, both foods are the SAME! (9).

Again, this is where the GI numbers are inaccurate.

CONCLUSION

This does not mean that we're to eat high GI carbs for the rest of our lives, and forget the low GI types.

Again, like everything, balance is the key.

But the take away message is that GI isn't the be all to end all for our health and body composition as it's sometimes labelled to be.

People who pay special attention to a glycemic index food list and think it will help their waistline don't realise their efforts are better being spent elsewhere.

When you're consuming protein, fat and fibre together with your chosen carbohydrate source - where your favourble carb source scores on the GI scale really isn't much of an issue.

The whole point is that the human body's reactions are not a simple thing that can be characterised by numbers on a scale.

If only it really were that easy.

The other point is, don't be fooled by people in marketing boardrooms who haven't a clue what they're talking about, yet throw around the "LOW GI" claims in an effort to grab your dollar, and have their product seen as one of the low glycemic index foods. 

So don't stress anymore about high and low GI.

Essentially, GI doesn't matter, and it's really not much of an important factor at all. 

 

"Stay Fit, Stay Flexed!"

 

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REFERENCES

(1) Aragon A. Elements challenging the Glycemic Index. Alan's Vault. 2006.

(2) Kiens B, Richter EA. Types of carbohydrate in an ordinary diet affect insulin action and muscle substrates in humans. Am J Clin Nutr  1996;63:47-53.
 
(3) Holt SH, Miller JC. A satiety index of common foods. Eur J Clin Nutr 1995 Sep;49(9):675-90.
 
(4) Raatz SK, et al. Reduced glycemic index and glycemic load diets do not increase the effects of energy restriction on weight loss and insulin sensitivity in obese men and women. J Nutr. 2005 Oct;135(10):2387-91.
 
(5)  Raben A. Should obese patients be counselled to follow a low-glycaemic index diet? No. Obes Rev. 2002 Nov;3(4):245-56.​
 
(6) Mosdol A, Witte DR, Frost G, Marmot MG, Bruner EJ. Dietary glycemic index and glycemic load are associated with high-density-lpioprotein cholesterol at baseline but not with increased risk of diabetes in the whitehall II study. Am J Clin Nutr October 2007 vol. 86 no. 4, 988-994.
 
(7) Park M. "Twinkie diet helps nutrition professor lose 27 pounds." CNN News. 2010 Nov 8.
 
(8) Holt, S.H., Miller, J.C., & Petocz, P. (1997). An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods. American Journal of Clinical Nutrition. 66, 1264-1276
 
(9) Ostman EM, et al.  Inconsistency between glycemic and insulinemic responses to regular and fermented milk products. Am J Clin Nutr  2001; 74(1):96-100.