Tuesday, 2 October 2012

The National Weight Control Registry: the gold standard in bullcrap (Part 3)

In Part 1 of this series on the National Weight Control Registry (NWCR), we looked at the pretty underwhelming response to the launch of the Registry, and in Part 2, we looked at the even more underwhelming results of 2-year follow-up. This was supposed to be a 3-part series. But as it turns out, the NWCR is just too ridiculously crap to tear apart in a mere 3 postings, without them turning into an actual book. Hey – there’s an idea. So welcome to the third instalment.

Just to recap on what we’ve done so far, in a country where over 70 million people are trying to lose weight, in nearly 10 years, a nationwide multimedia campaign managed to attract around 3000 people who have lost at least 30 pounds from their lifetime maximum weight and kept it off for at least a year, and of these, 72% were regaining weight – with most failing to lose it again.

But what’s happened since then you want to know. Well, erm, I dunno. The Registry was founded in 1994, making it nearly 20 years old. But the longest-term follow-up data published to date is the 2-year results I talked about in Part 2. I’m guessing, the researchers saw which way the wind was blowing, and decided not to pursue that avenue of research.

So they admitted the Registry had failed to provide evidence of the achievability of long-term weight-loss in the vast majority of people and moved on to bigger and better things? Did they hell! In the intervening years they have provided a steady stream of published peer-reviewed papers that have contributed pretty much nothing to the scientific debate on weight-loss maintenance. Let’s have a look at one of those papers, shall we?

In 2009, they published a paper comparing 2-year follow-up (there’s that magic number again) in people who had earned their place on the registry by losing weight following weight-loss surgery (WLS) and those who had used non-surgical (NS) methods. Of the less than 5,000 people recruited in the 13 years the registry had been running (not including those who were pregnant or had not been in the registry for at least 2 years), 105 had had WLS. These were matched 2:1 with NS participants, by age, gender, weight at entry (not BMI, so not taking into account height), weight loss within plus or minus 15.9 kg range (that’s a 70 lb range people – not how I would define ‘matched’) and weight loss maintenance duration at entry within plus or minus 2 years (so up to a 4-year difference; see above comment). So we have 315 people in total who were apparently ‘similar’ at baseline, by some interesting definition of the word ‘similar’. But overall, to be fair, those differences evened out and the two groups, if not the individuals in them, did appear pretty similar at baseline.

OK, 1-year follow up: of the 105 WLS entrants, 78 of them made it to 1 year, a dropout rate of 26%; the drop-out rate was lower in the NS group, only 18%. At 2 years, they hadn’t lost too many more WLS entrants – total dropout rate was 31%; disappearances of NS participants had shot up, making up for lost time, and were now at 35%. Now I’ve mentioned before that people drop out of studies for all sorts of reasons, but we can assume that at least some of them gained weight and were too embarrassed to participate further.

The NWCR makes no attempts to chase-up dropouts. It has been suggested to me, by a practitioner with an interest in obesity, that this is reasonable, because the ones who gain weight are not of interest to researchers. I beg to differ. These were the people who were touted, with much fanfare, as successful weight losers, and whose number, as far as I am aware, are still included in the registry total. I want to know what, if anything, went wrong. Did they stop exercising 2 hours a day? Did they go back to eating a moderately normal amount of food? Did they get treatment for their eating disorders? Or did their bodies just give up the charade and fight back? Sadly, we may never know.

But anyway, looking at the results of the ones who chose to continue to return their surveys in the pre-paid envelope each year, the first thing to notice is that method of weight loss didn’t seem to make much difference to results. The trajectory of weight/loss gain was similar between the two groups. After 1 year, this trajectory showed a small number continuing to lose weight (defined as more than 5kg (11 lbs) below baseline) – around 12% in the WLS group and 9% in the NS group, and these numbers didn’t change much over the second year. Where it gets interesting is in the other two groups. At year 1, around 60% of the WLS group and 68% of the NS group were classed as ‘maintainers’. ‘Maintenance’ is defined as being weight ‘stable’ within plus or minus 4.9kg (giving you around 22 lbs of wiggle room – we really should buy these poor scientists a dictionary). By year 2, those numbers had dropped to around 50% in both groups.

So if you’re not losing, and you’re not ‘maintaining’… ah, yes, the regainers. At 1 year, around 28% of the WLS group and 22% of the NS group had gained more than 5 kg (11 lb) since entering the registry a mere 12 months earlier. At 2 years, those numbers had increased to approximately 36% and 42% respectively. So much for the long-term ‘permanent’ weight loss associated with bariatric surgery. So just to be clear, each year, the number of people managing to ‘maintain’ their initial NWCR-entry weight dropped, and those gaining fairly noticeable amounts of weight increased. And when we look at what happened after 2 years, oh, wait, the NWCR doesn’t do more than 2 years in their publications. I wonder why.

But alright, after 2 years, around 60% were at least ‘maintaining’ their initial weight loss (actually, not really their initial weight loss for the most part, but the one that got them into the NWCR). Remember, as I mentioned in Part 1 of this series, 91% of registry members had previous ‘failed’ weight loss attempts, with the average amount of weight lost since they started trying to lose weight being 565 lbs. Some had lost over 1000 lbs before successful managing to keep off their current minimum of 30. Or 40, or 50 or whatever the average NWCR weight-loss at entry is supposed to be. And each year, more and more of them are gaining it back. Impressive, eh. And let’s not forget also that that 60% is 60% of the ones still standing at 2 years, and only 2/3 of the 315 initially entered into this particular study. If you do the analysis the way you’re supposed to (if you practice respectable science) and take into account all the people who started the study, not just the ones who finished it, only 40% are maintaining or better, even after WLS, pretty much in line with what we’ve seen in the registry as a whole.

Just as a point of interest, both groups were averaging about 1400 calories a day, and participants in the WLS group were getting significantly more of their calories from fat, eating fast food more often, and breakfast less often than the NS group. So much for lifestyle change. The WLS group were also exercising about half the amount of the individuals in the NS group (and doing about 1/3 of the amount of high-intensity exercise). To be fair (I seem to be saying this a lot – I’m trying to be fair – they’re not making it easy), the NS group were averaging over 3000 kcals per week of exercise. Or in English, equivalent to walking around 30 miles a week. And the range was huge – some were doing double this. So doing half of this amount isn’t exactly slacking. But the WLS group also reported more depression and stress at entry, and both groups showed significant increases in intensity of depressive symptoms after 1 year. These questions weren’t asked in Year 2. In both groups, the rates were much higher than community norms, with 30% of the NS group and 44% of the WLS group having clinically significant depression 1 year after entry into the registry.

But getting back to the fun stuff: for my finale, may I present to you, drum roll please, the abstract of this study. For the non-scientists among you, the abstract is like a summary of the paper that goes at the front and gives people an idea of what’s inside. It is also the source of press releases and the like. This would all be good and dandy if the abstract bore any resemblance to what was really in the paper. But let’s have a look. Each abstract includes a Conclusion, where the authors summarise their overall findings. If you are a busy doctor, or a busy press officer, this is probably the only bit you look at, after the title so it’s kind of important.  Just in case you’re interested, the title was “Weight loss maintenance in successful weight losers: surgical versus non-surgical methods”. Now I don’t know about you, but to me, that kind of suggests that weight loss was maintained and the ‘losers’ remained ‘successful’. It doesn’t say that as such, but I guess “Weight loss maintenance rates are pretty dire following both surgical and non-surgical weight loss, unhealthy behaviours are apparent at both ends of the spectrum, and the weight losers are pretty damn unhappy to boot” doesn’t have quite the same gravitas. But the title is at least more or less descriptive. And in conjunction with the conclusions, will give most people their take-home message from this study. So what were the conclusions? I’ll let the authors speak for themselves.
“Despite marked behavioral differences between the groups, significant differences in weight regain were not observed. The findings suggest that weight loss maintenance comparable to that after bariatric surgery can be accomplished through non-surgical methods with more intensive behavioral efforts.”
It’s worth noting that, again, cleverly, these conclusions do not say anything actually false. Differences were not really observed between the groups. But the way it is written, if not read carefully, might seem to suggest that significant weight regain did not occur, and that would be somewhat misleading. But not as misleading as the second, also not untrue, sentence. Yes, similar results can be achieved. But they’re still CRAP results people. Man up and admit it already! Tune in next time for more of why the NWCR is a disgrace to science and public health. I’m having too much fun to stop now!

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