But what if eating a lot of fructose can actually cause diabetes and weight gain? Well, when a sugar molecule gets too big, then it tends to bond with other molecules of the same size. One of these bonds causes a chain reaction, causing the sugar to start working its way through the bloodstream. This process can lead to serious damage to your blood vessels, leading to heart disease and other health problems. The best advice you can take at this point is to cut back on the amount of sugar that you consume, but don’t cut out entirely.