Lose Weight with Cold Rice!? Resistant Starch, the Non-Fattening Carbohydrate

The "Starch" That Changes with Cold Rice──What is Resistant Starch?

It might surprise you to hear that "chilled rice is good for dieting." When we actually researched and tried it, we found that cooling cooked rice leads to "starch recrystallization (retrogradation)," which increases the amount of indigestible resistant starch (RS). This resistant starch acts like dietary fiber, feeding beneficial bacteria in the large intestine and producing short-chain fatty acids that help regulate the gut (Sonia et al., 2015, and other studies).

Expected Benefits of Resistant Starch

Satiety and Calorie Intake Suppression

Because RS is difficult to digest in the small intestine, digestion and absorption after meals are slowed, making it easier to feel full for longer. A clinical trial reported that consuming 48g of RS suppressed appetite (Bodinham et al., 2010). When we tried eating a lunch centered around cold rice, we also noticed that the feeling of fullness really lasted, which naturally reduced our afternoon snacking.

Improving Blood Sugar Levels and Insulin Sensitivity

RS helps to gently slow down the rise in blood sugar after meals, and research shows it may also contribute to improved insulin sensitivity. Since review reports suggest it can be useful for managing diabetes and metabolic syndrome, it's definitely worth discussing with your doctor about incorporating it into your routine (Bindels et al., 2015).

The Gut Environment and Its Impact on Chronic Disease

Short-chain fatty acids like butyrate, which are produced during the process of RS fermenting in the large intestine, serve as a source of nourishment for the intestinal lining and are expected to help reduce inflammation. There are even reports showing they can have a positive effect on slowing the progression of chronic inflammatory bowel diseases and kidney disease (Jacobasch et al., 1999; Vaziri et al., 2014). However, since results can vary from person to person and differ depending on the type of study, it's best to keep our expectations realistic.

A Practical Guide to Cold Rice Recipes: How Do You Make It? How Do You Eat It?

Basic Recipe

The key is to "cook → cool rapidly → store in the fridge." After cooking, let the initial heat subside, then cover it with plastic wrap and chill it in the refrigerator for at least 8 to 12 hours. This is said to be the best way to increase the RS (studies often use a cooling period of about 12 hours). Even if you reheat it, the RS isn't completely lost and will remain to some extent.

Tips for Safe Storage

To prevent food poisoning, it's safest to put your cooked rice in the fridge (ideally at 4°C or below) within two hours of cooking, and finish eating it within 24 to 48 hours. If you've cooked a large batch in a big pot, spreading it out in a thin layer will help it cool down much faster. We also like to cook a big batch at night to use for lunch or bento boxes the next day, but we always make sure to keep it refrigerated and consume it within a short timeframe.

Recommended Ways to Enjoy It

Eating cold rice like a salad, chilled onigiri, chilled chazuke (with cold dashi broth poured over it), or even chilled potatoes and beans will all increase RS, so I highly recommend mixing and matching them. When I made a pancake-style dish using cold rice in the morning, it really kept me feeling full and satisfied (one study reports that combining RS with protein increases fatty acid oxidation).

Things to Keep in Mind and Real-World Pitfalls

While I've shared a lot of the great benefits so far, there are a few things we need to keep in mind. First off, just because the resistant starch (RS) increases doesn't mean the rice becomes "zero calories." Your overall energy balance is still the foundation of weight management, so we shouldn't expect rapid weight loss just from eating cold rice. It's also worth noting that the amount of RS used in research studies is quite high—around 48g—and it can be difficult to get that same amount just from our daily portions of cold rice (Bodinham et al., 2010).

Also, since everyone's body is different and some people may experience gas or bloating, it's best to start with a small amount to let your body adjust. If you are currently being treated for diabetes or have any underlying health conditions, please consult your doctor or a registered dietitian before adding it to your routine.

Summary

Resistant starch, which increases when you cool cooked rice, offers promising benefits like improving your gut health, helping you feel full, and gently moderating blood sugar spikes. We've actually tried incorporating cold rice into our own daily routine, and we definitely noticed a decrease in our afternoon snacking. However, it isn't a magic cure-all, so please don't forget to keep an eye on your total calories, overall dietary balance, and proper food safety. If you'd like to give it a try, just stick to these basics: "cook and cool," "refrigerate promptly," and "start with a small amount to let your body adjust."

Disclaimer: The information in this article is for general informational purposes only and does not constitute medical advice. Please consult a qualified healthcare professional before making any health-related decisions.