Junkfood Science: Not so fast — details of weight loss success tell a different story

June 08, 2007

Not so fast — details of weight loss success tell a different story

The message to fat people this week has been clear: there’s no excuse for not losing weight and keeping it off. According to news reports, a new government study had shown that long-term weight loss is not only possible, but many are doing it, and those who think otherwise "are just plain wrong."

Had this single study actually disproven a century of research, and the findings of every independent expert review of the evidence, showing that diet and exercise don’t work longterm?

Afraid not. This study not only didn’t prove any of those claims, but its findings suggest that serious harm may be resulting from the national obsession with thinness and frenzy to lose weight — and were in evidence long before the government launched its all out war on obesity.

According to the Scientific American, which uncritically published the Reuters version of the story that found its way around the world:

Many Americans do maintain weight loss

....Government researchers found that of 1,310 U.S. adults who'd ever lost a substantial amount of weight, the majority had managed to keep at least some of the weight off. Overall, 59 percent were still close to their weight of a year before -- which in all cases was at least 10 percent lower than their heaviest all-time weight. Another 8 percent weighed less than they did a year earlier. However, one third of the subjects had regained a significant amount of weight over the year, the researchers report in the American Journal of Preventive Medicine.

Lost pounds are notorious for finding their way back again. So it's "encouraging" to see that so many people in this study were keeping their weight stable, lead study author Dr. Edward Weiss told Reuters Health....

Still, weight maintenance remains a “challenge" in a culture that encourages sitting and eating, according to Weiss and his colleagues at the Centers for Disease Control and Prevention in Atlanta.... While relatively few people kept losing weight over the year, the study found, a majority managed to stay within 5 percent of their weight from the year before. Exercise seemed to be one of the factors that separated the regainers from the maintainers...

Let’s look a little more closely.

Successful losers defined. These researchers used the database of in-home interviews from the 1999-2002 National Health and Nutrition Examination Survey (NHANES), a continuous annual survey of the U.S. civilian, non-institutionalized population. Based on self-reported weights, they found 1,310 adults who one year earlier had weighed at least 10% less than their all-time highest overweight or obese weight. These 1,310 were the people identified has having successfully lost significant weight. What the researchers didn’t report is that this number represented only 6% of those surveyed.

Maintaining weight loss? Of these, only 98 people (7.5%) continued to lose weight during the one-year study period. The rest were regaining their lost weight! At the one-year mark, most (59%) had thusfar regained up to about half (5%) of the weight they’d lost, with 33.5% having already regained most of what they’d lost, or more. [They neglected to share full details on the extent of the rebound.] Clearly, there is no evidence of any sustained weight maintenance, even during this brief one-year study.

To arrive at those they deemed successful weight loss maintainers, however, they combined those who were losing with those regainers who were still within 5% of their starting weight. That was the “nearly six in ten [who] were able to maintain their original weight loss” being reported in the news. Not quite the “encouraging” success we might have thought.

Translating these weight changes, a successful maintainer could be a 5-5 woman weighing 148 pounds at the beginning of the year and 156 at the end; or 5-10 man weighing 174 pounds at the year's beginning and 183 at the end. Given the typical trajectories of regain, next year they’d likely have shot past their starting weight. But this study, of course, didn’t look long-term.

The biggest, fastest losers were also the biggest and most likely regainers, they found. This concurs with the entire body of evidence on intentional weight loss. The risks of weight regain “were significantly positively associated” with the weight lost, according to the researchers, with 3 times greater risks for those who’d lost 20% of their maximum weight.

Yo-yoing thrives in dietland U.S.A.

“Watch your weight” leaves you fatter! Another finding that didn’t make the news: In sharp contrast to popular wisdom, the researchers reported that “attempting to control weight [was] also significantly associated with weight regain” — nearly 2 times higher odds compared to those who weren’t trying to watch their weight.

This has been well recognized in the medical literature and repeatedly shown in clinical studies, even though it flies in the face of government admonitions to watch our weight and telling us we all need to try to control our weight to prevent obesity!

Exercise is the secret — or is it? Concerning physical activity, the researchers concluded: “The current study found that those who met public health physical activity recommendations for improving health were no more likely to regain weight than those who met higher recommended levels. The optimal dose and intensity of physical activity for preventing weight regain may depend on individual factors not analyzed in this study.” So beyond meeting activity levels for good health, more wasn’t better.

They did, however, say that those who were sedentary or “not meeting public health recommendations for physical activity” were twice as likely to be among the regainers. There are several glaring problems here, however. This study likely under-counted physical activity for all but the most obsessive and intense exercisers. Their data was based on asking the participants how much moderate to intense physical activity they’d done over only the past 30 days and during their leisure time. It was assumed this brief snapshot accurately represented the entire year. Yet, someone doing physical work all day, as in construction or housecleaning, would be considered among the sedentary. Also, few consumers view brisk walking, gardening, dancing or other non-“exercise” endeavors as being sufficiently intense to count as exercise; even though 30 minutes of such movement, most days of the week, has been shown all that’s necessary for metabolic fitness.

These researchers, however, used 60-90 minutes daily of moderate to vigorous activity to define the optimal dose and intensity required to meet public health recommendations for maintaining weight loss. Their source was the 2005 Dietary guidelines, even though it had little scientific basis for its recommendations. As William Dietz, M.D., Ph.D., director of the Division of Nutrition and Physical Activity at the Centers for Disease Control and Prevention had said, it’s unknown if there is an amount of exercise — or what it would be — that can prevent obesity or maintain weight loss. Ideally, if we’re really concerned for people’s health, enjoying physical activity shouldn’t be about weight loss.

Exercise, the researchers told Reuters this week, is one key for success, but “has to be accompanied by continuing calorie control.” A recent examination of the evidence, however, found that diet and exercise is not an effective way to lose weight or keep it off, and any form of weight loss comes with significant risks that are seldom mentioned.

Weight loss intent. A significant detail these researchers failed to include in this study was if the weight changes were intentional or unintentional. We can glean some idea of this from a study published last July in the same journal conducted by these same researchers using half of the same database (the 2001-2002 NHANES). They had reported that more than half of the people, and at all BMI ranges, had been trying to control their weight during the one-year study period. Most people were eating less, exercising more, and eating low-fat, low-calorie meals. And among those dieters who were “obese” at the beginning of that study, more than three-quarters were meeting recommended calorie restrictions — 50% more than “normal”-weight dieters. Once again, dispelling popular myths that blame fat people for overeating and not trying hard enough.

Dieting or signs of anorexia? In this current study, among those defined as successful weight losers, 38% were “overweight” at the beginning of the study, BMIs which have been shown even by multiple CDC studies to be the range with the lowest mortality. But 42% were not even “overweight”— they had had normal or below normal BMIs.

Worrisomely, another detail they neglected to flesh out or reveal was just how many of these thin people were continuing to diet and lose weight? And how many were among those obsessively exercising to lose weight? Again, their data last year revealed that 30% of women and 10% of men who were underweight or normal weight were still trying to lose weight! This is a very concerning indication that public health messages could be contributing to disordered eating and overexercising for weight loss — with serious health consequences for those of all sizes.

Jeopardizing seniors? Another particularly troubling finding in their data was that 49% of those defined as successfully losing substantial amounts of weight were seniors over the age of 55, with 34% of losers over age 65 — ages for which weight loss of any type significantly increases risks of mortality and is not recommended. Those over age 65 were also half as likely to regain the weight they lost, leaving them at greater risk. Again, these researchers failed to note how many were inappropriately dieting. Last year’s study indicated that at least half of the senior women and one-third of the men in most age ranges were trying to manage their weight. The researchers also didn’t reveal how many seniors had unintentionally lost weight because of health problems or undereating and being undernourished, and were inappropriately included among those considered to have “successfully maintained” their weight loss.

Overall, we have another study that bears little resemblance to what we’re hearing. In fact, this study not only fails to support the government’s public health messages for diet and exercise to prevent or manage weight gain, it gives us every indication that it may be contributing to harm.

Once again, an epidemiological study looking for correlations among a group of people can appear to support whatever agenda it was designed to find. But such studies never give us the full story.

Spin is everything. No matter how intuitive their conclusions might seem or how popular, epidemiology can never provide credible evidence to support decisions about our diet, lifestyle, or health ... and least of all, form a sound basis for public health policies or clinical guidelines.

© 2007 Sandy Szwarc

Thanks Lara!

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