Banana is a very nutritious fruit and known to be a sugar-laden, and calorie-packed fruit. An average or medium banana (7–8 inches long and 118 grams) contains 27 grams carbohydrates, 14 grams sugar, 105 calories (439,32 kilojoules), 3.1 grams fiber, and 1.29 grams protein. Compared to most fruits, bananas are very high in energy and carbohydrates. This high amount of energy or carbohydrate is what gives banana the bad reputation of not being “good” for weight loss or for individuals on a low-carb or keto diet.

Although bananas have a bad reputation for weight loss, they can still be incorporated as part of a healthy diet when trying to lose weight. To lose weight, you need to consume at least 1500 calories per day to provide the energy you need for daily living and regular physical activity. Therefore, eating a single fruit such as banana will not make you gain or lose weight. The balance of what you eat throughout the day, together with your daily physical activity, will determine the outcome on your weight loss, especially in the long term.

Banana sizes with their calories, carbohydrate, fiber, protein, sugar, and potassium content

The number of calories and other nutrients in banana depends on its size as summarized below:

  • Extra small (shorter than 6 inches, 81 grams): 72 calories, 19 grams carbohydrate, 2.11 grams fiber, 0.88 grams protein, 9.88 grams sugar, and 290 milligrams potassium.
  • Small (6–7 inches, 101 grams): 90 calories, 23 grams carbohydrate, 2.63 grams fiber, 1.1 grams protein, 12.3 grams sugar, and 362 milligrams potassium.
  • Medium (7–8 inches, 118 grams): 105 calories, 27 grams carbohydrate, 3.07 grams fiber, 1.29 grams protein, 14.4 grams sugar, and 422 milligrams potassium.
  • Large (8–9 inches, 136 grams): 121 calories, 31 grams carbohydrate, 3.54 grams fiber, 1.48 grams protein, 16.6 grams sugar, and 487 milligrams potassium.
  • Extra large (9 inches or longer, 152 grams): 135 calories, 35 grams carbohydrate, 3.95 grams fiber, 1.66 grams protein, 18.5 grams sugar, and 544 milligrams potassium.
  • Sliced (1 cup, 150 grams): 134 calories, 34 grams carbohydrate, 3.9 grams fiber, 1.64 grams protein, 18.3 grams sugar, and 537 milligrams potassium.
  • Mashed (1 cup, 225 grams): 200 calories, 51 grams carbohydrate, 5.85 grams fiber, 2.45 grams protein, 27.4 grams sugar, and 806 milligrams potassium.

Why are bananas good for weight loss strategies?

Banana is very beneficial when trying to lose weight due to the following benefits:

It slows digestion and makes you eat less frequently.

Bananas are very rich in fiber. That is, a medium banana contains 3.1 grams of fiber. Fibers are good for weight loss. This is because fiber slows down digestion, keeps you full for longer, and makes you eat less frequently. Research reveals that consuming only 30 grams or more of fiber per day is a simple and reasonable alternative to lose weight without following complicated diet programs.

Improve digestion and help feed gut bacteria.

Banana is rich in two groups of digestive enzymes called amylases and glucosidases. These enzymes help to digest complex carbohydrates into smaller molecules that can easily be absorbed. Therefore, banana helps to improve digestion and contribute to gut health.

Bananas reduce the risk of heart diseases, cancer, and diverticulosis.

In addition to weight loss, the fiber in banana comes with long-term health benefits. Eating large amounts of fiber has been linked to reduced risk of weight and fat gain, reduced risk of heart disease, diverticular disease, and some cancers.

Banana keeps blood sugar levels stable for diabetes people.

The sugar in banana occurs mainly in the form of glucose, fructose, and sucrose. The glycemic index (GI) of a food is an assigned value which reveals how quickly and how high those foods cause increases in blood glucose levels. GI lower than 55 is low, 56–69 is medium, and 70 or above is high. Banana has a GI of 42–62, depending on ripeness. The riper the banana is, the higher the GI.  Therefore, banana is said to have low to medium GI . This means that banana keeps your blood sugar levels relatively stable and minimizes the risk of sugar spikes especially for people with type 2 diabetes that are trying to lose weight. In fact, research demonstrated that consuming 250 g/day of banana is harmless both in diabetic and hypercholesterolemic patients.

Side-effects of eating banana

Bananas rarely cause any side effects when eaten in moderation. However, side effects of eating excess banana include bloating, gas, cramping, softer stools, nausea, vomiting, migraine, and hyperkalemia. Also, some people with latex allergy experience allergic reactions on consuming banana.

Who should avoid eating banana?

Not everyone can eat banana freely.  Bananas and other foods high in potassium should be avoided by people with advanced kidney disease to safeguard their kidneys and heart from damage. Also, foods high in potassium can interfere with some medications used for high blood pressure and heart failure. But it will take more than one banana to raise potassium to dangerous levels. However, speak to your doctor if banana is safe for you to consume.

How many bananas should you eat per day?

Eating multiple bananas per day will make you full and keep you from adding more variety into your diet, such as other macronutrients, including proteins and healthy fats. This could lead to nutrient deficiency and possible weight gain. For optimal health and healthy weight, eating a varied and well-balanced diet is key.

That said, the amount of banana consumed per day depends on your general health condition or your unique calorie and nutrient needs. According to the USDA, it is recommended to eat between two to four (2 to 4) medium banana per day. Banana can be consumed at any time of the day and even before sleep. Eating a banana before bed makes you sleep better. This is because its magnesium, potassium, and tryptophan content help to relax muscles and hence promote sleep. It also contains serotonin and melatonin which help regulate your sleep-wake cycle.


Bananas are a very nutritious fruit rich in calories, carbohydrates, starch, and fibers. They are also a major source of potassium, vitamins, and inflammation-fighting antioxidants. Bananas are incredibly low in protein. A medium banana (118 grams) contains only 1.29 grams of protein. Combining bananas with other foods such as vegetables, nuts, or proteins will create a balanced diet which not only complements your weight loss goals but also reduces the risk of cancer, diverticulosis, and heart diseases. Eating banana is also beneficial for diabetes patients trying to lose weight. However, banana should be eaten in moderation at least two to four per day to avoid side effects. Individuals with medical conditions or medications sensitive to potassium should avoid bananas.