[ip26]

Carbohydrates used to come from fruits (with fiber), vegetables (in small amounts & with fiber), and starchy vegetables (starches are complex & slow to digest). Today, carbohydrates are consumed in simpler forms and refined to be more concentrated.

In the former case, they digest slowly. In the latter case, they digest quickly. The practical implications of this are immediately obvious if you have ever heard of glycemic index and glycemic load, but in short, fast digestion & large quantities results in a big spike in blood sugar which is hard on your body & leads to diabetes.

Also important is that the original forms of carbohydrates came with all kinds of other nutrients. A sweet potato includes vitamin A, vitamin C, manganese, copper, pantothenic acid, vitamin B6, potassium, niacin, vitamin B1, vitamin B2 and phosphorus. Sugar on the other hand is the quintessential "empty calorie", carrying no vitamins, minerals, only calories.