If you look at articles about East Asian countries in issues of National Geographic from the early 20th century, you will notice two things. One is that many of the people in East Asia were eating a lot of white rice. The other is that only the rich people and the sumo wrestlers were overweight. That's because the rich people and the sumo wrestlers were eating something besides rice and vegetables. Back in the 1930s, Dr. Walter Kempner realized that populations that ate a rice-based diet were slim and remarkably free of degenerative disease. After he started teaching his patients at Duke University in North Carolina in the United States to eat a diet consisting of white rice and fruit, they lost weight and reversed their type 2 diabetes. Many of his patients with type 1 diabetes were even able to cut their insulin doses. So why am I seeing studies that are trying to prove that white rice causes diabetes? The latest was just published in the British Medical Journal (BMJ).
One problem with the BMJ study is that it analyzed how much white rice people were eating, but it didn't account for how much food they were eating and what other kinds of food they were eating. It just looked at a dose effect between servings of rice and health outcomes. That approach is potentially misleading. For example, someone who is in training to become a sumo wrestler probably eats a lot more rice than the average Japanese person does. However, he also eats a lot more meat and drinks a lot more beer. Because of their training diet, sumo wrestlers gain weight and often get type 2 diabetes. Yet it would be extremely difficult for someone to gain enough weight to become a sumo wrestler or even stay overweight on a diet of white rice and vegetables. Therefore, it would be silly to blame white rice for a sumo wrestler's weight and blood sugar problems.
The BMJ study provides a classic example of a recurring problem I see in the scientific literature on nutrition. The researchers want to answer a question--in this case, whether white rice makes people fat and contributes to type 2 diabetes. The sensible way to answer that question would be to survey all of the available evidence and then see how it relates to Hill's considerations for establishing cause and effect in epidemiology. Instead, the BMJ study took a very biased view of only one kind of evidence and then did some fancy math. Then, they came up with a misleading result.
The researchers wanted to know whether consumption of white rice is linked to obesity and diabetes. So they gathered a bunch of studies that asked people about their rice consumption and that followed up to see which people gained weight and got type 2 diabetes. Then the researchers used a mathematical approach called meta-analysis to combine the results of the studies. The biggest problem with this approach is that the researchers chose only one kind of study for their analysis: cohort studies of people who weren't diabetic at baseline and who were eating whatever they felt like eating. This means that the researchers systematically left out studies that compared rice-eating populations to other populations, as well as the clinical studies of people who lost weight and reversed their diabetes after being taught to eat as much as they wanted of a diet based heavily on rice and vegetables.
We've known since the early 20th century that a high-fat diet promotes insulin resistance, which is the underlying problem in type 2 diabetes. In the early 1930s, a British researcher named H.P. Himsworth found that he could cause insulin resistance in healthy young men in a week by feeding them a diet that was 80% fat by calorie. As he replaced fat with starch in his test diet, his subjects' glucose tolerance improved. He got the best glucose tolerance with the starchiest diet he tested: 80% carbohydrate by calorie.
Starting in 1939, Dr. Walter Kempner found that he got great results by teaching his patients to eat a diet based on white rice, fruit, and fruit juice--plus some added sugar for patients who were losing too much weight on that low-fat diet. Kempner designed this extremely low-fat, low-salt, low-protein diet because many of his patients had kidney problems and high blood pressure. That was back in the days before blood pressure medications. The high carbohydrate content of this diet (>90% by calorie) and correspondingly low fat content helped to improve his patients' sensitivity to insulin. The Rice Diet Program that Dr. Kempner founded is still helping people lose weight and reverse their chronic illnesses, but now they do emphasize whole grains.