However, there is such a thing as over-consuming a good thing. Eating too many bananas can sometimes wreak havoc on the system. Eating too much of the fruit can lead to weight gain. The higher amount of sugar in ripe bananas can increase blood sugar levels which is bad news for diabetics. Because of its high potassium content, there is a chance that you develop hyperkalemia – a condition that impairs muscle and nerve function. The beneficial fiber in an unripe banana can cause harm as well. When eaten in excess the fiber can cause constipation and gas, damaging the GI tract and that gives way to several diseases.