Such a trial would not be ideal, because many dietary variables would differ between the two groups—calories and fats among them. The subjects would also know what diet they’re consuming, and so the study would not be done blindly (although, ideally, the physicians who treated the subjects and the investigators themselves would be unaware). Nonetheless, it would be a good starting point. Would those eating the carbohydrate-rich diet be more likely to become glucose-intolerant, hyperinsulinemic, and insulin-resistant? Would they be fatter and have a greater incidence of obesity, metabolic syndrome, and Type 2 diabetes? Would they have more heart disease and cancer? Would they die prematurely or live longer? These are the questions we need to answer.

Another question that needs to be addressed urgently regards the health effects of sugar and high-fructose corn syrup alone. Since the 1980s, as we discussed (see Chapter 12), sugar and high-fructose corn syrup have been exonerated as causes of chronic disease on the basis that the evidence was ambiguous. Since then, virtually no studies have been funded; there have been no attempts to clarify the picture. Today I can imagine no research more important to the public health than rigorous, controlled trials of the long-term health effects of sugar and high-fructose corn syrup.

For the past decade, the National Institutes of Health has been funding trials that test whether “lifestyle modification” will prevent diabetes and metabolic syndrome. But these trials are done only in the context of the conventional wisdom on diet, obesity, and disease. In the largest of these trials to date, the $150 million Diabetes Prevention Program, the lifestyle modification included 150 minutes of exercise each week and a low-fat, low-calorie diet. The results confirmed that such a program of diet and exercise will indeed prevent or delay the appearance of diabetes and metabolic syndrome, but they said nothing about what aspect of this lifestyle modification was responsible. Was it the reduction in fat calories or total calories? Was it the exercise? Or was it a change in the type of carbohydrates consumed or a reduction in the total amount of carbohydrates? As we discussed (see Chapter 19), even if the goal of a diet is to reduce calories by preferentially reducing fat, it will inevitably cut back on carbohydrates as well, and usually sugars in particular.*138