Bananas Fattening Properties and the Glycemic Index

Glycemic Index? How does that relate to the question: “Are bananas fattening“?

Wow, I know that sounds a bit on the complicated side, but if you’ll stay with me I’ll try to spell it out in plain English.

This is a follow up to the original post about Banana Nutrition Facts and the “bad” things about bananas.

If you recall, I said that you have to take the word “bad” with a grain of salt. Like most things in life – it depends. So, the question we are exploring is: Are bananas fattening?

In order to answer that question properly, we’ll need to explore the Glycemic Index (GI) and how eating foods with differing Glycemic Indexes (GI) affect your body.

So, first of all…

What is the Glycemic Index (GI)?

The Glycemic Index (GI) is a numerical index that ranks carbohydrates based on how fast they are converted to glucose (pure sugar)  within the body. The scale for the Glycemic Index (GI) ranges from 0 to 100. The reference point for all Glycemic Index (GI) values is pure glucose which has a GI of 100…It’s all downhill from there. The higher the GI, the faster the carbohydrates in the food are converted to sugar.

Glycemic Index (GI) values are measured by feeding human test subjects a fixed portion of the food (after an overnight fast), and then measuring  samples of their blood at specific intervals of time. The idea is that a high GI food will produce higher levels of sugar in the blood sooner than a low GI food.

Why is the Glycemic Index Important?

Your body performs best when your blood sugar is kept relatively constant. If your blood sugar drops too low, you become lethargic and/or experience increased hunger.  And if it goes too high, your brain signals your pancreas to secrete more insulin. Insulin brings your blood sugar back down, but primarily by converting the excess sugar to stored fat.  In most situations, this is NOT what you want.

To add insult to injury, the faster your blood sugar goes up, the greater the chance that your body will produce too much insulin to counter the elevated blood sugar levels. This will cause your blood sugar to fall too low again making you feel tired and hungry all over again. Obviously, this is a cycle that leads to unwanted weight gain and deteriorating health from excess fat accumulation (from the excess insulin).

This is precisely why some people say that bananas are fattening or “bad” for you since they are mostly carbohydrates and mostly sugar.

But, there is a wrinkle here…The insulin response from your pancreas happens as a result of the GI of the food, the AMOUNT of food you eat, and how fast you eat it. This concept is called Glycemic Load (GL). We’ll save the GL discussion for another post.

As an example of how Glycemic Load (GL) affects the body, you could eat a piece of hard candy and while the whole thing is sugar (near GI of 100) you would not see a huge increase in your blood sugar since the AMOUNT of food is low.  A banana falls into the same category, I mean, it’s only 105 calories. Not a big deal folks.

Should All High-GI Foods be Avoided?

For non-diabetics, there are times when a rapid increase in blood sugar and its associated rise in insulin levels may be desirable. A good example is during and after prolonged, strenuous exercise – like road cycling. Cyclists routinely ride for hours at a time and must fuel their bodies during the ride. Again, bananas are an ideal solution to this problem.

Since insulin helps the body store depleted glucose back into tired muscle cells, it’s absolutely desirable to eat a high GI snack both during and after a hard ride.  This actually helps the athlete recover more quickly so she will be ready for the next training session.

So, where do bananas stack up?

GI’s of 55 or below are considered low, and 70 or above are considered high. The banana actually ranks as low GI coming in with a score of 52 for a large banana.

I hope that made sense and shows you that the answer to the question: “Are bananas fattening” is not quite as simple as some would have you believe.

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