Good Calories, Bad Calories

The NIH is currently spending $200 million on a decade-long trial called Look AHEAD to test the hypothesis that if obese diabetics lose weight they’ll be healthier for the effort. This is “the largest, most expensive trial ever funded by NIH for obesity outcome research,” says the Baylor University psychologist John Foreyt, who is one of the trial’s principal investigators. But once again, the trial tests only the conventional wisdom. The goal of Look AHEAD is to induce five thousand obese diabetics to lose weight by the same lifestyle modification used in the Diabetes Prevention Program: cutting calories and fat calories, and exercising. If these obese diabetics do lose weight, and if they do end up healthier for it, we still won’t know whether it was the calories, the fat calories, the exercise, some combination of all three, or maybe just the carbohydrates or the sugar that made the difference. And we won’t know whether, if they restricted carbohydrates alone and ate protein and fat to their hearts’ content, they would have been healthier still.

Because these trials are planned as a test of only one hypothesis—and a poorly defined hypothesis at that—the research ensures that we won’t have the kind of reliable answers that we so desperately need. If the Diabetes Prevention Program had included a test of the carbohydrate hypothesis, the investigators could have compared the effect of a low-fat, low-calorie diet and exercise to the effect of carbohydrate restriction alone, and that would have told us whether it’s the carbohydrates or the calories and the sedentary behavior that cause these chronic diseases. If Look AHEAD were to include a test of the carbohydrate hypothesis, we might at least know the answer in another decade. It doesn’t, and we won’t.

The scientific obligation, as I said in the prologue, is to establish the cause of obesity, diabetes, and the chronic diseases of civilization beyond reasonable doubt. By doing so, we can take the necessary steps to prevent these disorders, rather than trying to cure them or ameliorate them after the fact. If there are competing hypotheses, it does us little good to test one alone. It does little good to continue basing public-health recommendations and dietary advice on association studies (the Framingham Heart Study and the Nurses Health Study are prominent examples) that are incapable of reliably establishing cause and effect. What’s needed now are randomized trials that test the carbohydrate hypothesis as well as the conventional wisdom. Such trials would be expensive. Like the Diabetes Prevention Program and Look AHEAD, they’ll cost tens or hundreds of millions of dollars. And even if such trials are funded, it might be another decade or two before we have reliable answers. But it’s hard to imagine that this controversy will go away if we don’t do them, that we won’t be arguing about the detrimental role of fats and carbohydrates in the diet twenty years from now. The public will certainly not be served by attempts of interest groups and industry to make this controversy go away. If the tide of obesity and diabetes continues to rise around the world, it’s hard to imagine that the cost of such trials, even a dozen or a hundred of them, won’t ultimately be trivial compared with the societal cost.

Notes

PROLOGUE: A BRIEF HISTORY OF BANTING

Epigraph. “Farinaceous…”: Tanner 1869b:219.

“…corpulence notoriety”: Anon. 1864b. “…size or weight”: Banting 1864:14.

“Knowing too that…”: Harvey 1872:69–70.

Banting began dieting: Banting 1864:18–19. “I have not felt better…”: Banting 1869.

United States, Germany: Banting 1869. “the emperor of the French…”: Anon. 1864c. “If he is gouty…”: Quoted in “banting” entry, OED 1989.

A paper was presented: Anon. 1864f. See also Anon. 1864d; Anon. 1864a. “is tolerably complete…”: Anon. 1864g. Banting responded: Banting 1869.

Banting acknowledged: Banting 1869. Alfred William Moore: Anon. 1864g. John Harvey: Harvey 1864.

Brillat-Savarin: Brillat-Savarin 1986 (“fat…,” 237–39; “…rigid abstinence…,” 251).

Dancel: Dancel 1864 (“All food…,” 59; “The hippopotamus…,” 54).

“We advise Mr. Banting…”: Anon. 1864g.

“fair trial” and “…starchy elements…”: Anon. 1864e.

“To attribute obesity…”: Mayer 1968:6.

Sir William Osler: Osler 1901:439–40. Oertel prescribed a diet: Oertel 1895. See also French 1907:951. Bismarck lost sixty pounds: Schwartz 1986:103–4. Ebstein insisted: Ebstein 1884 (“of meat every kind…,” 33).

“Foods to be avoided…”: Greene 1951:348.

“The great progress…”: Bruch 1957:352.

“The overappropriation…”: French 1907:14. Rony reported: Rony 1940 (“…marked preference…,” 59; “an extremely obese laundress…,” 62).

“In Great Britain obesity…”: Davidson and Passmore 1963:382.

“On the day of the races…”: Tolstoy 2000:200. “the dearth of proteins…”: Lampedusa 1988:255.