Friday, January 12, 2007

Only the data are slim. Part 1.

A minor disclaimer: I cannot promise that all of the embedded links will work, because a number of them are from subscription sources. Give it a shot.

NOTWITHSTANDING THE CEASELESS ADVERTISING and the knowing tone of the diet movement's celebrity leadership, the underlying data are shockingly scant. "It's amazing how few good studies have looked at weight loss," observes the Harvard School of Public Health's Dr. Walter Willett, one of the most influential figures in modern epidemiology. "The long-term evidence in particular is meager. We need much bigger and longer randomized trials."

Some of today's best-known diets reached cultural eminence, transforming American eating habits along the way, without being meaningfully validated for efficacy or even safety. (The cover story in the January 2004 Nutrition Action Newsletter featured a sidebar under the sly heading, "The Atkins Low-Evidence Revolution.") Today, Atkins' "low-carb" mantra is a ubiquitous social phenomenon; many restaurants now devote a boxed-off portion of their menus to "Atkins-friendly" dishes. Nutritionally speaking, the diet was also the progenitor of the biggest blockbuster of the new millennium to date, The South Beach Diet. Nonetheless, the very few scientifically rigorous studies of the diet cast doubt on its usefulness for genuine weight maintenance. Dr. James Hill of the Center for Human Nutrition, whom we met last year at around this time, says his studies of the people in his national weight-control registry show that Atkins dieters fare no better than others when it comes to long-term success—and may expose themselves to significant health risks in the bargain.

Or let's look at another popular (albeit unlikely) diet guru from recent years. In 2003's Ultimate Weight Solution: The 7 Keys to Weight Loss Freedom, Dr. Phil McGraw, who lacks any background in nutrition*,
evinced an all-embracing familiarity with the subject and its implications for weight management. He began by separating overweight readers into "pears" and "apples"—in itself, an unoriginal step. But McGraw went on to use his book as a sales pitch for a branded "Weight Management Supplement & Complete Multivitamin" system that, he claimed, was specifically targeted to each body type. The system included a dizzying array of supplements, anchored by the now-infamous Shape Up! line of health bars and shakes; these featured McGraw's ruddy face on the packaging, and were made by CSA Nutraceuticals, coincidentally owned by McGraw's former Texas business partner. McGraw insisted that the CSA regimen, which set hopeful consumers back about $120 a month, had "solid clinical evidence behind it." Among those who disagreed was Yale's Dr. Kelly Brownell, one of America's most visible and respected experts on diet and nutrition; "a recipe for making money" was how Brownell described the McGraw plan to the New York Times. Another top clinical researcher in nutrition, Jules Hirsch, dismissed the whole thing as "gibberish." Under threat of federal indictment, CSA in 2004 promised to stop distributing the products, and the whole mess eventually was resolved not in a lab—where it should've been assayed in the first place—but in a Los Angeles courtroom, where McGraw agreed late last year to fork over $10.5 million to consumers who felt defrauded. Even so, the paperback version of Ultimate Weight Solution remains a solid performer on Amazon. (It goes back to what I've said a thousand times: We don't want to hear what we don't want to hear.)

All popular diets play fast and loose with the few established facts we do have about weight management, promising benefits rooted in the flimsiest of data and/or extrapolated from studies with doubtful real-world relevance. Of the rush to anoint the natural protein leptin as the next weight-loss godsend, health blogger Phil Kaplan writes, "When scientists found that injecting leptin into an obese, genetically altered mouse with a [flaw in a specific gene] caused it to lose ½ of its bodyweight in 4½ weeks, needless to say they were thrilled. If you are a genetically altered mouse with [that genetic flaw], then yes, leptin injections may help…"

Also by their nature, diet books and mainstream plans reduce complex formulas and inscrutable biophysical processes to jacket copy. Taking the time to explain the real mechanisms of action—to the extent such mechanisms are even known—would require far too much qualification and thus soften the "punch" of the promise. For a good illustration, one need look no farther than the current holy grail of pop-culture weight loss, the glycemic index (GI). The GI is the core concept of the mega-best-selling South Beach Diet by Dr. Arthur Agatston, as well as any number of other faddish diet programs. Basically, the GI organizes foods into "slow carbs" and "fast carbs," the theory being that you want to build your menu primarily around foods that provoke a slow rise in blood sugar (low-GI) rather than a rapid one (high-GI).

But there's a problem right off: The GI isn't a constant. The same prepared foods and even raw food components test out with different GIs according to how they were grown, stored, cooked, etc. [See cover story from Nutritional Action Newsletter, linked above.] Take something as straightforward as plain old rice. White rice can be low-GI or high-GI, depending on whether it's Uncle Ben's converted (low) or instant (high). Ditto pastas: No universal GI consistency exists, even among specific types of linguine: Thin linguine yields a higher GI than thick linguine. Is the average dieter sophisticated enough—and sufficiently committed to doing his/her homework—to sift through all this? More to the point, should he/she be expected to have to sift through it all, after paying $50 or more for a book and its associated menu planners, or hundreds of dollars for membership in an online diet plan? The overarching irony is that GI-mania may be a house of cards anyway. No less a figure than Thomas Wolever, the University of Toronto researcher who helped develop the GI food scale (and later contributed to the more scholarly weight-loss book, The New Glucose Revolution), concedes that his branchild is no dieting panacea. "I've yet to see evidence that a low-GI diet aids weight loss," he says in that same Nutrition Action Newsletter cover story.

The crippling flaws in mainstream diet books are endemic to the process that brings them to market. For one thing, there's a strong impetus in publishing circles to have these books authored by celebrity doctors**
. This may seem sensible enough—who better to write a diet book than some doctor who "discovered" a fantastic new weight-loss method? In practice, the celebrity doctor seldom arrives at his insights after long-term affiliation with a large research hospital specializing in the medical aspects of nutrition. In fact, celebrity docs seldom are actively involved in clinical research. Often they're just selling a plan that they thought up based on anecdotal observations of their own patients—if that. Today's doctors-cum-authors may have little more to offer than a theory of how a certain weight-loss regimen might work, which they brainstormed with some hotshot literary agent, who then changed things around a bit strictly for marketing purposes. No joke, and not even much of an exaggeration. You'd be shocked at how many "breakthrough!" diets were conceived not in a lab, but by some agent and editor at a pricey New York bistro like Elaine's.

A former fitness editor I know puts it like so: "A lot of the agents and even the editors don't really care all that much if the information is true. The rule of thumb is that you find a study, any study, to back up whatever you wanted to say in the first place.*** Then you filter out anything that might contradict it. That way you haven't really lied to your readers. You've just told them something that's convenient for you to say." Convenient. And profitable. And false.

Such imperatives often put authors with nominal consciences in the position of having to use the interior pages of their books to distance themselves from the very promises made on the cover. In the most extreme cases, an author may have to distance himself from the whole point of his book. To wit, the following statement, which appears inside the hot-selling book Good Carbs, Bad Carbs: "In spite of the title…there are no bad carbs."

More to come....

* and who, cynics have observed, could stand to shed a few pounds himself.
** and preferably telegenic male doctors, who will play well on the morning shows.
*** Sadly, this is all too true of today's journalism as a whole.


Parkin said...

You say all popular diets do this, but what about W.W. (I hesitate to sound like an advert by naming the brand lol).

I know what you mean, you mean 'fad' diets, but lots of people go to W.W., and if you look at the rules set out in the book, they are those of a balanced healthy eating plan. If done 'properly' anyway:)

Steve Salerno said...

I think it's clear that, certainly in comparative terms, Weight Watchers is harder to attack than other diet programs. In head-to-head tests, WW consistently is ranked at the top of the heap among formal diet plans.

I do have a few quibbles with WW that are along the same lines as my quibbles with AA--having to do with its characterizations of the "chronicity" of weight problems. But (a) the (limited) medical literature may be on WW's side on this one and, more importantly, (b) I don't really want to get bogged down in a plan-by-plan analysis here. I'm looking more at the overall climate of weight management and why it has so horribly failed Americans--while raking in billions of dollars in the process.