Why Almost Everything Dean Ornish Says about Nutrition Is Wrong

Scientific American   Last month, an op–ed in The New York Times argued that high-protein and high-fat diets are to blame for America’s ever-growing waistline and incidence of chronic disease. The author, Dean Ornish, founder of the nonprofit Preventive Medicine Research Institute, is no newcomer to these nutrition debates. For 37 years he has been touting the benefits of very low-fat, high-carbohydrate, vegetarian diets for preventing and reversing heart disease. But the research he cites to back up his op–ed claims is tenuous at best. Nutrition is complex but there is little evidence our country’s worsening metabolic ills are the fault of protein or fat. If anything, our attempts to eat less fat in recent decades have made things worse.

Ornish begins his piece with a misleading statistic. Despite being told to eat less fat, he says, Americans have been doing the opposite: They have “actually consumed 67 percent more added fat, 39 percent more sugar and 41 percent more meat in 2000 than they had in 1950 and 24.5 percent more calories than they had in 1970.” Yes, Americans have been eating more fat, sugar and meat, but we have also been eating more vegetables and fruits (pdf)—because we have been eating more of everything.

What’s more relevant to the discussion is this fact: During the time in which the prevalence of obesity in the U.S. nearly tripled, the percentage of calories Americans consumed from protein and fat actually dropped whereas the percentage of calories Americans ingested from carbohydrates—one of the nutrient groups Ornish says we should eat more of—increased. Could it be that our attempts to reduce fat have in fact been part of the problem? Some scientists think so. “I believe the low-fat message promoted the obesity epidemic,” says Lyn Steffen, a nutritional epidemiologist at the University of Minnesota School of Public Health. That’s in part because when we cut out fat, we began eating foods that were worse for us.[...]

The point here is not that Ornish’s diet—a low-fat, whole food, plant-based approach—is necessarily bad. It’s almost certainly healthier than the highly processed, refined-carbohydrate-rich diet most Americans consume today. But Ornish’s arguments against protein and fat are weak, simplistic and, in a way, irrelevant. A food or nutrient can be healthy without requiring that all other foods or nutrients be unhealthy. And categorizing entire nutrient groups as “good” or “bad” is facile. “It’s hard to move the science forward when there are so many stakeholders who say ‘this is the right diet and no other one could possibly be right,’” Bazzano says. Plus, discouraging the intake of entire macronutrient groups can backfire. When people dutifully cut down on fat in the 1980s and 1990s, they replaced much of it with high-sugar and high-calorie processed foods (think: Snackwell’s). If we start fearing protein, too, what will we fill our plates with instead? History tells us it’s not going to be spinach.