Obesity is a major public health challenge in modern medicine. The World Health Organization (2020) defines obesity as a body mass index equal to or greater than 25 kg/m2 in Asian countries. Obesity is associated with several diseases, including metabolic syndrome, cardiovascular diseases, diabetes mellitus, fatty liver diseases, and cancer, leading to associated morbidity and mortality. Given the increasing prevalence of obesity and the limitations of conventional treatments, alternative strategies such as the "rice hack" have gained attention. This article delves into the effectiveness of rice-based dietary interventions for weight loss, examining the scientific evidence, potential benefits, and limitations.
The Rice Diet: A Historical Perspective
The Rice Diet, created by Walter Kempner, MD, in 1939, was initially designed to treat high blood pressure and kidney disease. The diet was extremely restrictive, consisting primarily of rice and fruit, with minimal protein, fat, and sodium. This approach aimed to reduce stress on the kidneys and lower blood pressure.
Kempner's Original Rice Diet
Kempner's original rice diet consisted almost entirely of fruit and rice, totalling 2,000 calories a day. The diet was dramatically low in salt, protein, and fat, and high in complex carbohydrates. The rice diet required a person to consume 4% to 5% of daily calories from protein, 2% to 3% of daily calories from fat, 150 milligrams (mg) of sodium daily and restricted daily intake of fluids. A typical diet in the United States, then and now, consists of 25% protein, 25% fat, and 50% carbohydrates, so this is very different from what a person would typically eat.
Early Results
The diet had clinically significant results, according to the Journal of the American Heart Association. Although 25 of the 192 people enrolled in his trial died and 60 people did not markedly improve blood pressure, 107 patients saw significant improvements in blood pressure. In 66 of 72 patients, there was a decrease in heart size, and 73 of 82 patients had decreased blood cholesterol levels. Diabetic retinopathy improved or disappeared entirely for 21 of 33 patients who experienced the condition.
Kempner published research in the Archives of Internal Medicine about the rice and fruit diet menu's effect on weight. In the study, 106 people with severe obesity followed the diet, along with an exercise prescription and daily motivational support. Each person lost at least 99 pounds, and average weight loss was 141 pounds. Many also experienced significant reductions in blood pressure, blood sugar and triglycerides.
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The Rice Diet Solution
More recently, a modified, less-restrictive version the Rice Diet was re-popularized by Kitty Gurkin Rosati's book The Rice Diet Solution, which claims that the eating program is effective for lasting weight loss. The Rice Diet Solution adapts Kempner’s guidelines to weight loss. The recommendations in this book include a calorie deficit, exercise, and other lifestyle changes.
The Rice Diet Solution has three phases. In each phase, people follow different versions of the diet for varying amounts of time per week. These versions are the basic rice diet, which consists only of starches and fruit, the lactovegetarian diet, which consists of starches, fruit, vegetables, and nonfat dairy and the vegetarian diet, which includes starches, fruit, vegetables, and some protein. Starches include rice, beans, and grains. Nonfat dairy can include skim milk or zero fat yogurt. Vegetarian protein sources include beans, pulses, and soy products. The diet includes 500 to 1000 mg of sodium daily, with a minimum of 300 mg per day.
Understanding the "Rice Hack"
The "rice hack" often refers to methods of cooking rice to reduce its calorie content, primarily by increasing its resistant starch content. Resistant starch is a type of starch that isn't digestible, so it is passed through the large intestine without ever being absorbed by the body.
Cooking Methods to Reduce Calories
Cooking rice, as below, can change the structure of the starch.
- Boil water.
- Add one teaspoon of coconut oil to every half cup of uncooked rice.
- Cook the rice as you usually would.
- After cooking the rice, refrigerate it for at least 12 hours.
- You can reheat rice whenever you want to eat it. The starch remains unchanged, making it an ideal diet food option.
Potential Benefits of Resistant Starch
- Improves Digestion: Resistant starch acts as a prebiotic.
- Enhances Satiety: Foods high in resistant starch can help you feel full longer.
Scientific Evidence for Rice and Weight Loss
Studies on Rice Bran Extract (RBE)
Rice bran extract (RBE) contains antioxidants (γ-oryzanol, tocopherols, tocotrienols, and ferulic acid) and can be used as a food supplement to lower systemic blood pressure and cholesterol, and regulate pancreatic function. However, the anti-obesity effect of RBE is still unclear.
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One study on male Institute of Cancer Research mice fed with a high-fat diet (HFD) for 8 weeks and then supplemented with 220 and 1,100 mg/kg/d RBE while the low-fat diet group (control) were not, showed that administration of RBE to HFD-induced obese mice reduced the body weight and adipose tissue mass compared with untreated mice. It also decreased blood vessel density in the adipose tissue. Furthermore, RBE downregulated Vegf and Mmp-2 mRNA levels in visceral fat tissue.
The Role of Angiogenesis and MMPs
Obesity involves adipose tissue growth due to an increase in fat cell numbers (hyperplasia) and/or size (hypertrophy) accompanied with remodeling of the adipose tissue extracellular matrix (ECM). Matrix metalloproteinases (MMPs) are critical during the growth of adipose tissue and its microvasculature. MMP-2 and MMP-9 control tissue development and microvessel maturation by modulating the ECM. Development and growth of adipose tissue are linked with angiogenesis and ECM remodeling as they require formation of new blood vessels to provide oxygen and nutrients to adipocytes. Obesity can be reduced by inhibiting angiogenesis, which subsequently reduces adipogenesis.
The study showed that the blood vessel density of both VSC and SC adipose tissues were lower in RBE treated mice than in untreated obese mice.
New Insights into Brown Fat Cells
A new source of energy expending brown fat cells has been uncovered by Harvard Medical School researchers at Joslin Diabetes Center, which they said points towards potential new therapeutic options for obesity. Specifically, the authors point to smooth muscle cells expressing the Trpv1 (temperature-sensitive ion channel transient receptor potential cation subfamily V member 1) receptor and identify them as a novel source of energy-burning brown fat cells (adipocytes). Brown fat, or brown adipose tissue, is a distinct type of fat that is activated in response to cold temperatures. Its primary role is to produce heat to help maintain body temperature, and it achieves that by burning calories. “The capacity of brown and beige fat cells to burn fuel and produce heat, especially upon exposure to cold temperatures, have long made them an attractive target for treating obesity and other metabolic disorders,” said senior author Yu-Hua Tseng, HMS professor of medicine at Joslin.
Practical Considerations and Limitations
Nutritional Adequacy
The Rice Diet is extremely strict. You’re going to cut way down on calories, salt, fat, and sugar - all at once. The food on the plan doesn’t give you enough calcium and vitamin D, so you will need supplements. Also, the plan offers much less protein than what’s recommended for healthy people. If you have a medical condition, check with your doctor before starting this diet.
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Sustainability
Following a strict and low-calorie diet like this one is going to be hard. It would be a real challenge to stay on the plan at social events or when eating out. Plus, there’s a risk for nutritional deficiencies. Restricting protein to less than half the recommended amount may lead to loss of muscle mass and won’t help keep you feeling full.
Potential Risks
Because the Rice Diet is very strict and low in calories, pregnant women, young children, and those with a history of eating disorders shouldn’t try it. A low-sodium diet may also be risky for certain people, such as older adults and those who do long-distance endurance exercise. Talk to your health care provider first if you’re thinking about trying the Rice Diet.
Who Should Avoid the Rice Diet?
The authors of The Rice Diet Solution advise that people taking drugs for diabetes, high blood pressure, or other cardiovascular diseases consult a doctor before trying this diet. In addition, people who have had surgery on their colon, ureteral diversion procedures, or impaired kidney function should not follow the diet. Anyone who feels unwell or dizzy while following the rice diet should stop following the program and speak with a medical professional.
Adapting the Rice Diet for Different Needs
You can adjust the Rice Diet to fit your dietary restrictions and preferences. If you’re vegetarian, you can have eggs for your lean protein. Beans, soy, tempeh, tofu, as well as soy- and grain-based milks are also recommended, making it suitable for vegans, too. The Rice Diet isn’t strictly a gluten-free diet because you can eat bread, crackers, and other wheat-based foods. But it can easily become gluten-free. Rice doesn’t have gluten in it, so you’re good there. But gluten is in many products that you might not know it’s in, so if you’re going gluten-free, you’ll need to read food labels.