Blog Diets The Banana Diet: Pros, Cons, and Everything Else You Need to Know

The Banana Diet: Pros, Cons, and Everything Else You Need to Know

The Banana Diet, also known as Asa-Banana, is an understudied weight loss approach with no strong scientific backing. However, it has gained significant popularity, largely due to its proponents, Sumiko Watanabe, a pharmacist and preventive medicine expert, and her husband Hamachi.

The couple claim this diet helped Hamachi lose 37 pounds and shared details of this on their website. They propose that starting the day with bananas and room temperature water can control hunger and boost metabolism (6).

So, does this diet really work? Should you consider incorporating it into your lifestyle?

In this comprehensive guide, we answer these questions and more, providing you with an in-depth look at the pros and cons of the Banana Diet.

What Is The Banana Diet?

The Banana Diet is a fad diet that gained popularity in Japan in the early 2000s. It involves consuming one or more bananas for breakfast, together with room temperature water. You can then eat whatever you want for lunch and dinner, as long as you don’t eat too late at night.


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The creators of this diet also recommend the following guidelines to help you achieve better results:

Eat Only Raw Bananas for Breakfast

The core principle of the Banana Diet is to consume raw bananas for breakfast. According to Sumiko and Hamachi, bananas are the best choice as they are cheap, tasty, don’t require any preparation and therefore, save time, and allow you to stick to the diet in the long term.

Regarding the number of bananas you should eat, the creators suggest you can eat as many as you want until you feel full. This is because they claim that it’s not about the number of bananas but rather how much it fills you up (1) (6).

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Chewing thoroughly, slowly, and mindfully is also an important aspect of this diet. This will help you feel more satisfied and reduce the chances of overeating.

If you don’t like the idea of eating raw bananas, you’re allowed to eat any other fruit. The only conditions are that it should be raw, and you can only eat one type of fruit for breakfast.

Frozen bananas are not allowed, nor any other frozen or cooked fruits. This is because the creators believe that frozen fruit chills your stomach.

Drink Water Frequently

For breakfast, you should drink room temperature water, preferably at least one glass. After that, you can sip on water throughout the day whenever you feel thirsty.

The creators of this diet don’t recommend any specific amount of water, but they suggest that you should listen to your body and drink whenever you feel thirsty (8).

They warn against drinking flavored beverages, saying that they may dull your palate and interfere with appetite control (3).

Read more: 7-Day Weight Loss Low-Carb Diet: Choose High-Protein, High-Fiber, or Ultra-Low-Carb

Have a Balanced Lunch and Dinner

For lunch and dinner, you can eat whatever you want as long as it’s not high in calories and doesn’t involve eating late at night.

The creators of the Banana Diet suggest that you should aim to feel full, not stuffed. Therefore, it’s important to listen to your body and stop eating when you start to feel full.

They recommend rice dishes and Japanese food in general. This may be because these foods are typically low in calories and high in nutrition, in addition to being culturally relevant to the creators.

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banana diet  

Snacks Are Allowed, But Not Required

The creators of this diet encourage snacking, particularly chocolate and Japanese sweets, but they are not required. They also encourage snacking on in-season or dried fruit.

Ice cream and dairy snacks are not recommended, and in place of these, rice is recommended.

Late Dinner Is Not Allowed

The creators of the Banana Diet are strict about not eating late at night. They suggest having dinner before 8 pm, ideally around 6-7 pm.

They claim that this helps with digestion and weight loss as your metabolism slows down at night. It’s also believed that going to bed on an empty stomach can lead to a better quality of sleep, which is important for your overall health (7).

Late Night Snacking Is Not Allowed

Similar to not eating late at night, the creators of this diet also don’t recommend snacking after dinner. They believe nighttime snacking can lead to blood sugar spikes, bloating, and weight gain.

When you feel like you want a snack at night, they recommend drinking some water slowly to help curb cravings. As a last resort, you may have the same type of fruit you had for breakfast.

Go to Bed By Midnight

The creators of the Banana Diet also suggest going to bed before midnight, as they believe getting enough sleep to be important for weight loss. This may be related to research that shows a link between poor sleep habits and obesity (5).

They recommend sleep hygiene practices such as eating dinner at least three hours before bedtime and having a routine to wind down and relax before you go to sleep.

Alarm Clocks Are Not Allowed

The Banana Diet creators also discourage the use of alarm clocks. They suggest allowing your body to wake up naturally, which may promote better sleep and a healthier lifestyle overall.

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They claim that waking up to an alarm can cause stress to the brain, which is transferred to the large intestine and may interfere with bowel movements.

Exercise Is Not Required

Another distinctive aspect of the Banana Diet is that it does not require any specific exercise routine. This may be appealing to those who don’t enjoy or have time for traditional workouts.

Instead, the creators recommend light exercise such as walking and stretching, in addition to incorporating everyday physical activities such as swinging your arms (6).

They discourage overweight individuals from engaging in strenuous activities, as they believe it can cause injury.

Solution for Overeating

Sumiko and Hamachi recommend that you rest if you have overeaten. They discourage intense exercise as this may fatigue your body, which is already working hard to digest the food you just ate. Instead, they suggest drinking water and getting some rest to allow your body to recover.

Keeping a Diet Diary

The final recommendation of the Banana Diet is to keep an open diary online and share your progress with others. This will help you stay accountable and motivated, as well as allowing you to receive support from others who are also following the diet.

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Does The Banana Diet Work?

There is no scientific evidence that supports the claims of the Banana Diet, and it should not be seen as a miracle solution for weight loss. Any diet that overly emphasizes one food or restricts certain foods can be unhealthy and unsustainable in the long term. 

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Furthermore, some claims made by the Banana Diet, such as that frozen fruit is harmful, are also not backed by scientific research. Neither Sumiko nor Hamachi are qualified nutritionists or dietitians and it’s important to consult a healthcare professional before starting any new diet.

That being said, some principles of the Banana Diet can be beneficial to incorporate into a healthy lifestyle, including:

  • Drinking enough water – research has shown that adequate hydration plays a role in weight management and overall health (8).
  • Eating more fruit – the most recent dietary guidelines recommend that individuals consume 1.5-2 cups of fruit per day (6).
  • Having balanced meals – incorporating a variety of nutritious foods in appropriate portions can help maintain a healthy weight and prevent nutrient deficiencies (4).
  • Eating mindfully – chewing slowly, tuning into your body’s hunger and fullness cues, and being aware of what you’re eating can help with weight management (6).
  • Getting enough sleep – research has shown poor sleep patterns to be linked with obesity, and getting adequate rest is essential for overall health (5).
  • Avoiding late night snacking – consuming excess calories late at night can lead to weight gain and disrupt sleep (7).
  • Being physically active – regular physical activity is essential for both physical and mental health (2).
  • Keeping a food diary – tracking food intake can help increase self-awareness and make healthier choices, but it doesn’t work well for everyone.

banana diet  

Can I Lose Weight by Eating 3 Bananas a Day?

No, simply eating three bananas a day will not guarantee weight loss. Weight loss is dependent on a variety of factors, including genetics, metabolism, overall diet and lifestyle habits, and physical activity levels. While incorporating more fruit into your diet can be beneficial for your health, it should be part of a well-rounded and balanced approach to nutrition.

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A three-day banana diet plan for weight loss may give temporary results, but it is not a sustainable or healthy long-term approach. It’s important to focus on creating healthy habits and making gradual changes to achieve lasting weight loss and overall well-being.

Do Bananas Burn Belly Fat?

No, there is no scientific evidence that supports the claim that bananas specifically target belly fat. While bananas are a nutritious and filling fruit, they do not have any magical powers when it comes to weight loss. To burn belly fat, a combination of a balanced diet and regular exercise is required.

It’s also important to remember that spot reduction (targeting a specific area for fat loss) is not possible. Fat loss occurs throughout the body, at a pace that is determined by individual factors, and cannot be targeted to a specific area.

Can I Eat Only Bananas for a Week?

It’s neither recommended nor healthy to eat only one type of food for an extended period. A mono diet, such as the Banana Diet, can lead to nutrient deficiencies and potentially harm your health.

While following a restrictive diet may result in short-term weight loss, it’s not sustainable or beneficial for long-term health. It’s important to focus on balanced and varied meals that provide all essential nutrients for overall well-being.

Read more: 24 Weight Loss Smoothies, 2 Diet Plans, and 5 Belly Fat Smoothie Secrets

banana diet  


  • Can I eat 1 banana a day for weight loss?

Yes, you can incorporate one banana a day into your diet for weight loss. Bananas are low in calories and high in dietary fiber, which helps with digestion and makes you feel full, which reduces the likelihood of overeating. It’s important to remember that weight loss is a multifaceted process that involves a nutritious diet, regular exercise, and a calorie deficit.

  • Can I eat a banana on an empty stomach?

Eating a banana on an empty stomach is not harmful and some people may prefer it this way. However, you shouldn’t do this in the hope of losing weight. There’s no special outcome to eating a banana on an empty stomach and it’s more important to focus on overall dietary patterns for weight management.

  • Is a banana a day too much sugar?

A medium-sized banana contains approximately 14 grams of sugar. This is a natural sugar that is found in fruits and is different from added sugars that are found in processed foods. 

While it’s important to monitor your overall sugar intake, eating a banana a day is not excessive and can be part of a healthy diet. It also provides essential nutrients, including potassium and vitamin C, that are beneficial for overall health (1).

  • Which fruit is best for weight loss?

There isn’t any one specific fruit that is best for weight loss as all fruits have their own unique nutritional profiles. However, fruits that are high in fiber and water content, such as watermelon, berries, oranges, and apples, can help you feel more satisfied with fewer calories, which makes them a great choice for weight management. As with all food, moderation and variety are key.

The Bottom Line

The Banana Diet may not be a scientifically-backed solution for weight loss, but some of its principles can be beneficial for overall health when they are incorporated into a balanced lifestyle. As with any diet, it’s important to consult a healthcare professional before you make any significant changes to your eating habits.


This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!


  1. 9 Potential Health Benefits  of Bananas (n,d,
  2. Benefits of Physical Activity (2022,
  3. Confection Confusion: Interplay Between Diet, Taste, and Nutrition (2021,
  4. Healthy balanced diet (2020,
  5. Sleep deprivation and obesity in adults: a brief narrative review (2018,
  6. The Morning Banana Diet (2009,
  7. Unhealthy eating habits around sleep and sleep duration: To eat or fast? (2018,
  8. Water – a vital nutrient (2021,
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