Starches are digested to sugars, and they may indeed have similar effect on blood sugar in some cases, but the article did not say "75 percent carbs", it said "75 percent sugar". "Sugar" usually means HFCS or sucrose, both of which contain a high proportion of fructose, which is metabolised differently to the pure glucose you get from digesting starch. Additionally, there's some evidence that taste influences overeating, and starch does not have the sweet taste of sugar. Japan has the longest life expectancy in the world and their diet includes large quantities of rice, so starch is not obviously harmful.