Last updated on April 18th, 2017
“What Is the ‘Best Diet’ for You?” asks US News and World Report. According to the magazine’srankings, the DASH Diet is the best overall. Atkins and other low-carb approaches finish in the second-division. Despite claims of a rigorous methodology, the rankings betray a conventional and increasingly suspect thinking about fat, carbohydrates, and health. The usual low-fat/ high-carb approach wins because it is presumed to be balanced, healthy and effective. But presumption is not proof.
“DASH” is an acronym for “Dietary Approaches to Stop Hypertension;” the diet was originally developed to treat adults with high blood pressure. US News and World Report classifies it as a “balanced” diet that is good for the heart and nutritionally sound, and pairs it to the Mediterranean Diet, which placed second in the overall category. DASH encourages followers to eat plenty of fruits, vegetables and whole grains with some lean protein and to avoid red meat, sweets and salt. Only 20-35% of daily calories come from fat, and less than 10% come from saturated fat. DASH is said to provide “the recommended amount of carbohydrates.” This would apparently be the government’s recommended amount of carbohydrates, which are lots and lots. In short, DASH is a typical low-fat, high-carb diet.
The Atkins Diet placed 19th out of 20 in the overall rankings, with only the Paleo approach (also low-carb) coming in behind it. A few other lower carb approaches made it up into the middle rankings, including the South Beach (13th), Eco-Atkins(14th), and Glycemic-Index Diets (16th).
Looking over the rankings and the comments, it seems obvious that to be considered “heart healthy” a diet had to be low-fat. To be “nutritionally sound,” it had to be balanced — meaning that it had to include plenty of carb-heavy foods (i.e., grains).
Exactly what if any science these criteria rest on is anybody’s guess. The report bases its case on the collective opinion of a “panel of experts,” a black-box in effect. We get the results of the panel’s deliberations, and the identities of panel members, but little of the scientific reasoning or evidence behind the results.
Familiar assumptions about the connection between dietary fat and health seem to prevail inside the black-box. For instance, Dean Ornish’s extremely low-fat diet (which ranked 8th overall) was characterized as “nutritionally sound, safe, and tremendously heart-healthy.” The knock against it was that the “severe fat restriction the diet demands” would be hard to adhere to, not that adhering to it would be anything other than a terrific idea. That is assumed. To take another example, the 3rd ranked diet overall is Therapeutic Lifestyle Changes (TLC), which the report describes as “another very solid diet plan created by the NIH.” The NIH (National Institutes of Health) has pushed the low-fat approach for decades, so we know what kind of diet TLC is. For good measure, it is endorsed by the American Heart Association, another long-standing low-fat advocate. The report gushes that TLC “has no major weaknesses, and it’s particularly good at promoting cardiovascular health.” It restricts fat; what else do you need to know? Of courseit is heart healthy!
It’s the standard doctrine, the received wisdom. No evidence required.
As for the Atkins Diet, it scores high only for short-term weight loss. The report implies that weight-loss only lasts for two weeks. It complains about a lack of long-term studies of the Atkins Diet’s effectiveness and safety (and whose fault is that, NIH?) and about “all that fat” which “worries most experts.” The report cites this damning evidence against Atkins: “You don’t even have to trim it off your steak.”
Fat on a steak. The horror, the horror!
Yes, all that fat worries most of the experts in US News and World Report’s black-box, just as it worries the NIH and AHA. Whether it should worry any of them, or us, is the question. A thorough, impartial examination of the scientific evidence would argue otherwise, but magazine articles seldom go in for that sort of thing.
(The article was originally posted on my JimA’s blog on June 7, 2011.)