The Bananas for Breakfast Diet, also called the Morning Banana Diet or Banana Diet, was developed in Japan by pharmacist Sumiko Watanabe and her husband. Although the rules are relatively simple, it does involve a bit more than just eating a banana at breakfast.
What to Eat
On the banana diet, you start your morning with room-temperature water and as many bananas as you like. Follow with whatever you would like to eat at lunch, an afternoon snack and dinner. The only restrictions are that you can't have desserts; you must eat dinner by 8 p.m.; you must go to bed before midnight. Some versions of the diet prohibit alcohol and dairy products.
Theory Behind the Diet
Bananas contain resistant starch and fiber, both of which can be filling. Eating plenty of bananas at breakfast may fill you up enough so you eat less later in the day. Going to bed earlier at night can help limit sleep deprivation, which has been linked to a higher risk for obesity, notes EveryDiet.org.
You need to cut calories or exercise more to lose weight. This diet doesn't have any calorie restrictions, so on this diet you may actually end up gaining instead of losing weight, says registered dietitian Kerri Glassman in an October 2008 article on CBSNews.com. A medium banana has about 105 calories, which isn't too high, but most of the calories in this diet are likely to come from the foods you eat at lunch and dinner, which aren't restricted. This diet may help people who would typically eat a lot of sweets or overeat after dinner for emotional reasons, because it allows for sweets only during the afternoon snack and doesn't allow eating after dinner.
There are some potential problems to eating a lot of bananas in the morning, according to an article published in the "New York Daily News" in October 2008. The sugars in bananas are particularly sticky and can increase your risk for cavities if you don't brush your teeth after breakfast. Bananas also can be constipating. A breakfast containing just carbohydrates, such as bananas, may also cause your blood sugar levels to spike, so diabetics may want to avoid this diet.