Low calories and fat but high fibre. Although bananas are a little higher in calories and carbohydrates than some fruits, they are not considered a high-calorie food. A medium banana has around 92 calories,less than many diet snack foods that contain around 100 calories. Bananas also contain very little fat,about 0.5 grammes in one banana,but are very rangr of B vitamins, vitamin C, folic acid,magnesium and calcium. So bananas contribute to a healthy and balanced diey whether you are trying to lose weight or not.