Bananas Fattening Truths

Myths, Truths and info about natural foods…including bananas

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.

Health Benefits of Bananas

Many people enjoy bananas, but they also help to promote the healthy functioning of the human body…

 Health Benefits of Bananas

  • High Potassium content helps promote Cardiovascular Health
  • Natural antacid effects help soothe ulcers
  • Promote effective digestive function
  • Protect against vision loss as you age
  • Promote bone health through easier absorption of Calcium
  • May reduce risk of kidney cancer

High Potassium content helps promote Cardiovascular Health

Bananas are one of the best available sources of potassium, which has been cited as essential to maintaining normal blood pressure and heart function.  A medium sized banana has about 475 mg of potassium and only about 1 mg of sodium, which makes the fruit nearly ideal for getting about 135% of the RDA (350 mg) without a lot of trouble.

Natural antacid effects help soothe ulcers

Bananas have long been recognized for their soothing effects on stomach acid production.  Bananas accomplish this through two mechanisms:

  • Bananas help activate the cells that make up the lining of the stomach encouraging them to produce a thicker coat of the protective mucous that lines the stomach to provide a barrier against the destructive effects of the stomach’s acid.
  • Bananas contain compounds known as protease inhibitors that help reduce populations of stomach bacteria linked with ulcers

Promote effective digestive functions

The pectin contained in bananas has been shown to normalize and regulate the movement of food through the digestive tract

Protect against vision loss as you age

Antioxidant vitamins A, C and E have been shown to reduce the onset of vision decline as humans age.  Since bananas are an excellent source of these vitamins, they may help delay vision decline as you age.  Ophthalmology studies have shown that 3 servings of fruit a day may delay the natural onset of age-related macular degeneration (ARMD).

Promote bone health through easier absorption of Calcium

Potassium has been shown to help counteract the urinary loss of calcium exacerbated by the high salt diets of many Americans, thus helping to avoid bone loss related to poor diet.  Green(er) bananas contain short chain fatty acids (SCFA) that are indigestible to humans but help promote the cellular health of the digestive tract itself.  Pectin in bananas helps increase nutrient absorption by the intestine.

May reduce risk of kidney cancer

Bananas contain high concentrations of antioxidant phenolic compounds which have been shown to reduce the risk of kidney cancer.


Bananas Nutrition Facts

So, let’s start with the basics question first:  Are Bananas fattening?

The simple answer to that question is that no food in and of itself is fattening.  It depends on what you eat it with, when you eat it and most importantly how MUCH you eat.  Another HUGE factor is how much you exercise.  So, in order to answer that question a bit more thoroughly, we will begin by looking at the basic nutritional information about bananas.

What are the basic nutrition facts of the banana?

Basic Banana Nutrition Facts

According to, here is the basic nutrition data for a medium sized banana (7″-8″ long):

  • Carbohydrate: 27 grams (3g fiber)
  • Protein: 1g
  • Fat: none
  • Calories: 105

Vitamins in Bananas

  • Vitamin A –  75.5IU
  • Vitamin C –  10.3mg
  • Vitamin E (Alpha Tocopherol) –  0.1mg
  • Vitamin K –  0.6mcg
  • Riboflavin –  0.1mg
  • Niacin –  0.8mg

Minerals in Bananas

  • Calcium –  5.9mg
  • Iron –  0.3mg
  • Magnesium –  31.9mg
  • Phosphorus –  26.0mg
  • Potassium –  422mg
  • Sodium –  1.2mg

Good things about bananas:

  • Low in saturated fat
  • Low in cholesterol
  • Low in sodium
  • Good source of dietary fiber
  • Good source for Vitamins C and B6, Potassium and Manganese

“Bad” things about bananas:

  • Most of the calories come from sugars

But, here’s where you have to be careful about judgement calls like “bad” things about bananas.  First of all, the sugar is natural and not refined sugar or corn syrup.  Secondly, your body runs on sugar, so you have to pay attention to the context.  What I mean is that, it depends on when you eat the banana and what you eat with it.

You may know that bicyclists LOVE bananas.  They are perfect for maintaining your energy on a long bike ride.  That’s because of the sugar.  Since sugar hits your bloodstream quickly a banana will give you a quick boost of energy.  So the judgement of whether the sugar is “bad” for you depends on how much load your body is under when you eat the banana.  More on this in a later post.