Quite a lot of answers here, but nobody really answers the question directly: Eating rice is NOT equivalent to eating sugar. Rice will become glucose in the body, while sugar is a 50/50 mixture of glucose and fructose.
Also, everybody’s talking about blood sugar levels, but that’s not the whole story. Fructose, for example doesn’t even raise the blood sugar(glucose) level, but it’s still bad – it’s significantly worse than glucose, for several reasons:
1. Fructose can’t be used by most cells of the body, so most is metabolized in the liver, with effects similar to alcohol (after all, alcohol is made from fructose). Excessive fructose consumption might contribute to non-alcoholic fatty liver disease.
2. Fructose oxidizes proteins about 7 times faster than glucose. Oxidation of proteins occurs naturally in the body, rendering the proteins unusable. (Search for “advanced glycation end products”). This is also why a high blood sugar level isn’t good.
3. Fructose is converted to fat more “efficiently” than glucose. I don’t know the exact number right now, but I think it was about 30 %, while only 10 % of glucose is converted to fat. (Yes, those numbers only apply for the specific amount used in that study, but other amounts shouldn’t change that ratio too much.)
So, what’s with rice? Sure, rice has a higher glycemic index than sugar (that’s because half of sugar – the fructose – doesn’t contribute to the blood sugar level), but the glycemic index itself doesn’t say much.
Rice isn’t usually eaten separately. If eaten in a meal with other food, the glycemic index of rice (and with other foods as well) decreases dramatically.
Generally, fat, acid (e. g. vinegar) and fiber are responsible for that. So be careful with “low-fat”-meals…. (I don’t think much of the whole “low-fat-movement”, anyway).
So: If you eat rice in a meal, the glycemic index is often only half the value found in the tables – for normal amounts of rice, the resulting blood sugar level is no problem. And the body needs glucose, after all.