Are bananas ‘fattening’?

Are bananas ‘fattening’?

This is one of the questions I get asked by most of my clients! Let’s have a look at whether bananas influence weight loss or weight gain…

Nutritional content of bananas

Bananas contain mainly carbohydrates in the form of glucose, sucrose and fructose. It does not contain much protein or fat. 1 small size banana will provide around 377 kJ and 1 medium size banana, 440 kJ. Bananas are good sources of antioxidants e.g. catechins, certain vitamins and minerals.

A medium size banana contains:

  • Potassium:12% of the DRI (Daily Reference Intakes).
  • Vitamin B6:20% of the DRI.
  • Vitamin C:17% of the DRI.
  • Magnesium:8% of the DRI.
  • Copper:5% of the DRI.
  • Manganese:15% of the DRI.
  • Fibre:1 grams.

Calorie contribution of bananas

Should you eat 1 medium-size banana, it contributes to roughly 5 - 7% of your daily energy intake (assuming you consume about 6000 - 8000 kJ per day). Therefore, one can safely say that a banana does not contain a lot of calories.


Fibre content of bananas

Bananas are quite high in fibre (3.1 gram per medium banana). An adult requires about 25g of fibre daily. Fibre is important for digestive health and is also a source of inulin, which is a prebiotic. Prebiotics, serve as food for probiotics, which in turn promotes a healthy gut flora. The protective effect of fibre on the prevention of heart disease, certain cancers and diabetes are well documented. It is also known that fibre makes you feel full for longer, which may help you eat fewer calories over the long term. This has also been proven by a few studies linking increased fibre intake to reductions in weight.

The Glycemic Index (GI) of bananas

The greener the banana, the lower the GI, because it contains more resistant starch than ripe bananas. This means that Resistant starch slows down the absorption of sugar from foods. This keeps your blood sugar levels stable and helps you feel full. Resistant starches are long chains of glucose (starch) that are resistant to digestion. Studies show that this type of starch benefits weight loss and can reduce blood sugar levels. Ripe bananas have a higher GI than greener bananas. The sugar content increases as the banana matures, which in turn affects your blood sugar levels. So, to favour weight loss, stick to greenish bananas, although bananas in general release its sugars slowly and has a low to medium GI (GI score of between 40 and 62).

The final verdict

Although not as filling as apples and oranges, bananas are perceived to be one of the more filling fruits, and most people enjoy eating a banana before training. Bananas can certainly fill your tummy more than other high calorie ‘empty’ snacks.


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Bananas are healthy and contains various nutrients. They don’t contain a lot of calories. They are high in fibre and have a low to medium GI, and therefore won’t spike your blood glucose levels. Bananas are rather filling too. If you are trying to lose weight, there is nothing wrong with including bananas as part of a healthy balanced diet.

Claudine Ryan, Registered Dietitian, RD (SA)

Written by : Claudine Ryan, Registered Dietitian, RD (SA)

Claudine Ryan holds a Bachelor of Science degree in Dietetics and is registered with the Health Professions Council of South Africa. Claudine is passionate about people and their health, and enjoys helping others to optimise their health and manage their chronic lifestyle related diseases through sound nutritional therapy and practical advice.