Bananas are quite effective in losing weight because they are low in calories and rich in dietary fiber. Bananas are sweet, so people will think that the calories must be high. In fact, the calorie of a banana (net weight about100g) is only 87 calories, which is only about half lower than that of a white rice (150g, 220 calories). In addition, bananas contain almost all vitamins and minerals, so you can easily get all kinds of nutrients from bananas. Bananas contain a lot of potassium and magnesium. Potassium can prevent blood pressure from rising and muscle spasm; Magnesium can relieve fatigue.