The staple starch in China has been rice for a few thousand years and they have grown to 1,300,000,000 people. It is only in the past 10 to 15 years that diabetes has become, quite suddenly, a major problem in China. It is not easily explained by rice consumption alone but by increased use of refined rice coupled with a shift in work patterns and subsequent lack of exercise. China has become more westernised in lifestyle and a lack of exercise appears to be the cause of the rise of diabetes, together with greater consumption of refined carbohydrates.
It is the rate at which the refined starches are metabolised together with, because of reduced activity, the lower levels of hormones and ezymes in the blood plasma which are normally required to aid the various cell functions that causes the imbalance. It is not the starch itself. You can't have diets which rely on a high proportion of refined starch if you are not very active. You have to cut down on starch, switched to unrefined starch or become more active. Or combine all three.
Whilst you can do without starches altogether, the Inuit and Saami have been doing it for a few millenia, you cannot easily switch to their diets either. A traditional Inuit diet would result in serious internal bleeding for most modern westerners after a few years. The extent to which human population groups have, through natural selection, become genetically adapted to suit their lifestyle and food supply is only recently becoming apparant. Our lifestyle, and food supply have both changed dramatically in the past few decades and we start to see the results.