Sugar is vital to the body, though in moderation. Its excess in the blood is detrimental to health, leads to obesity, and sometimes to diabetes. Anciently sugar came into the body with various products, where it is contained in slight concentrations, thus it was hard to get a surplus. As for pure sugar, it consists almost entirely of sucrose, and we tend to overeat it. The sweet taste deceives our organism, which in the process of evolution got used to other concentrations of so necessary sucrose.