Bananas are oddly controversial for a fruit when it comes to determining whether they'll make you gain (or lose) weight fast. Due to their carbohydrate content, some people avoid bananas in the belief that even eating two bananas a day will cause weight gain.
Meanwhile, at the other end of the pop-fitness spectrum, some raw eaters use bananas as the bulk of their diet and claim it helps them maintain their physiques. However, with little straightforward information to be found, carb-conscious dieters are left wondering if bananas will help or hurt their efforts.
There is no evidence to suggest that bananas will cause you to gain weight unless eaten in excess.
Don’t Fear Bananas
There's no evidence to suggest that eating a bunch of bananas will make you gain weight fast — at least not more than any other food. The Harvard T.H. Chan School of Public Health says that there is no evidence that bananas cause weight gain.
The T.H. Chan School goes on to cite a long-term study of more than 100,000 participants, published in PLOS Medicine in September 2015, about the effects of different fruit and vegetables on weight. The study found that banana consumption was linked with less weight gain over time, though not as strongly as apples, pears, and berries.
When eaten in excess, just like anything else, your body will store the energy as fat – but there's no reason to think that eating a bunch of bananas, specifically, is a way to gain weight fast. One large banana has about 121 calories.
If you're eating multiple bananas a day in addition to your regular meals, it could be easy to end up eating more calories than you need. With that said, bananas are a good source of potassium and other nutrients, and overall have a better nutritional profile than, for example, a cookie.
Bananas and Fiber
It's not as easy to mindlessly throw back bananas the way you might with other foods, probably because bananas contain fiber, which helps with satiety, according to the U.S. Food and Drug Administration.
This would suggest that as long as they're eaten in moderation, bananas can certainly be part of a weight loss plan. The carbohydrate also promotes "digestive regularity." Even though bananas might alarm carb-phobes, the fiber in bananas slows the rate at which they're digested, preventing the blood sugar spike you might get from sugary desserts.
There's evidence speaking to the proven and suggested health benefits of fiber, such as a September 2014 study in the journal Gut, which showed an association between high-fiber intake and reduced risk of the intestinal disease diverticulosis. Additionally, a July 2015 study in Diabetologia pointed to an association between high-fiber diets and lowered Type 2 diabetes risk.
Read more: How to Make Bananas Last Longer
The Glycemic Index
For all the concern about the quantity of carbohydrates in bananas, it's worth considering the quality of those carbs. Glycemic index refers to how much a food that contains carbohydrates raises blood glucose, according to the American Diabetes Association.
Research suggests that consuming low GI foods can help manage weight and fend off obesity-related illnesses, such as one meta-analysis published in June 2013 in the journal Nutrition, Metabolism, and Cardiovascular Diseases.
Depending on their ripeness, bananas have a low to medium GI, with underripe bananas having the lowest, according to a glycemic index search tool provided by the University of Sydney. This means that bananas in general won't cause the blood sugar spikes you might see from eating some other carbohydrate-laden foods, such as white bread. For this reason, bananas, especially when underripe, may be helpful in effecting weight loss.
- USDA FoodData Central: "Banana, Raw"
- Harvard T.H. Chan School of Public Health: "Bananas"
- PLOS Medicine: "Changes in Intake of Fruits and Vegetables and Weight Change in United States Men and Women Followed for Up to 24 Years: Analysis From Three Prospective Cohort Studies"
- U.S. Food and Drug Administration: "Dietary Fiber"
- Diabetologia: "Dietary Fibre and Incidence of Type 2 Diabetes in Eight European Countries: the EPIC-InterAct Study and a Meta-Analysis of Prospective Studies"
- Gut: "Source of Dietary Fibre and Diverticular Disease Incidence: A Prospective Study of UK Women"
- Nutrition, Metabolism, and Cardiovascular Diseases: "Long-Term Effects of Low Glycemic Index/Load vs. High Glycemic Index/Load Diets on Parameters of Obesity and Obesity-Associated Risks: A Systematic Review and Meta-Analysis"
- University of Sydney Glycemic Index Food Search