Which is more effective for dieting... warm rice vs. cold rice?

The staple food of Koreans is rice. Most people prefer freshly cooked warm rice over cold rice. However, in reality, cold rice is more beneficial for dieting and blood sugar management. Why is that?

Resistant starch is high in cold rice and is effective for dieting. Resistant starch is a type of starch (amylose) but contains up to 90% dietary fiber, making it different from regular starch, which is mostly composed of glucose. Regular starch has a high glucose content, and consuming it in large amounts can increase body fat. In contrast, resistant starch does not tend to be stored as fat. It must be broken down into glucose to be stored as fat, but resistant starch is not broken down into glucose. Additionally, resistant starch provides a longer-lasting sense of fullness compared to regular starch. Resistant starch with high dietary fiber content is not digested in the stomach but passes to the intestines where it is fermented by microbes. After fermentation, some is absorbed by the body, but the rest is excreted in the stool. Because it takes a long time to reach the large intestine from the stomach and small intestine, even a small amount of resistant starch can keep you feeling full for a long time.

Resistant starch slowly raises blood sugar levels and is also good for blood sugar management. In the 2019 journal 'Nutrition & Diabetes,' research results showed that resistant starch improved insulin resistance in overweight or obese diabetic patients. When blood sugar rises rapidly after a meal and the pancreas over-secretes insulin repeatedly, insulin resistance develops. This is a phenomenon where blood sugar is not properly regulated even when insulin is secreted. Insulin resistance is also a major predisposing factor for the development of type 2 diabetes.

However, storing in the freezer to cool quickly is meaningless. When the temperature drops, the starch molecules move and clump together to form resistant starch, but freezing prevents this structural change from occurring properly. This is because the water around the starch freezes instantly, making it difficult for the molecules to move. When cooling rice, it is better to store it in the refrigerator rather than at room temperature, as this promotes better conversion to resistant starch. According to a study published in the Asian Pacific Journal of Clinical Nutrition in 2015, white rice cooled at 4°C for 25 hours and then reheated had 20% higher resistant starch content than rice cooled at room temperature for 10 hours.

<Source: Health Chosun>