posted by fatfu
One of the things you often hear – even among fat activists – is that 95% of weight loss attempts fail long-term. It sounds like an impressively discouraging number, but still, it leaves us with the idea that 5% of fat people are able to leave their corpulence behind and join the world of respectable, acceptable, normal-weight humanity. Or at least get somewhere in the vicinity.
We should be so lucky. When weight loss failure numbers are presented (generally 80-95% failure) “success” doesn’t mean achieving “normal weight” – let alone permanently. It means the ability to keep off some very modest amount that a given researcher (usually with a vested interest in the weight loss strategy) has arbitrarily defined as ”weight loss success.” Typically 5-10% weight loss maintained anywhere from 1 to 5 years.
If that’s enough to make you thin, then I have news for you: you weren’t fat.
And studies that look at “successful losers” – unusual as they are even when defined by such a low bar – find the overwhelming majority are in the process of regaining, they’re just taking a little longer than average in getting back to baseline.
In reality, people who go from “obese” to “normal weight” and maintain it for more than a few years are so rare that nobody knows just how rare because no weight loss study has been large enough or rigorous enough to detect a significant number of them. You can look everywhere (and I have) for a respectable study that gives you this number and you won’t find it.
Weight Watchers – More like Two in a Thousand Success Rate?
But Weight Watchers has sort of spilled the beans on this well-kept secret. At least it gives us a number to start making deductions. They come in a recent article published in the British Journal of Nutrition by Michael Lowe, an assuredly unbiased Weight Watchers consultant, who hopes to convince us that successful weight loss is more common than the studies say. Mainly by spinning really horrible numbers in the best possible light.
His study is an update of one he did in 2001, and since the current article is pay per view, and I’m too cheap and ornery to spend my money on an article promoting the diet industry, I went with the 2001 version, which examined results from the early 90s. Yes, the older results are slightly worse than the newer results appear from the abstract, but as you’ll see later – it hardly matters.
Lowe surveyed Weight Watchers participants who became “Lifetime Members” in the years 1992 to 1996 to see how they did after one to five years. Lifetime Members are only “the most successful” Weight Watchers members who achieve their “goal weight” (usually a BMI of 25) and maintain it for 6 weeks. After that they get to attend for free.
Apparently Lowe felt we could better appreciate how well Weight Watchers works if we confine our examination to the people who do incredibly well on it. I bet the pharmaceutical companies wish they could get away with that.
Anyway it seem relevant to know how representative the lifetime members are – that is how many Weight Watchers members actually reach their goal weight. The article doesn’t say. Naturally. Somewhere towards the end Lowe admits that the these people are only a “fraction” of the people who join Weight Watchers, but he doesn’t let us in on what fraction they are. Just that there have been 189,000 from a five-year period. Or 38,000 per year (give or take).
38,000 people who reached goal weight per year sounds like a lot. But actually it turns out to be a really small number. I found a business article from back then that stated that Weight Watchers had 600,000 attendees in the U.S. in 1993. Divide 38,000 lifetime members per year into 600,000 and my calculator says that each year only about 6% of Weight Watchers members (give or take) reached their goal weight (presumably 94% failed).
Now before you get all impressed with Weight Watcher’s 6% success rate, let’s step back. For one thing, the successful 6% weren’t so fat in the first place. The 2001 study says that most were between a BMI of 25-30 (i.e. “overweight” but not “obese” – to use definitions I find silly). The 2007 abstract says the average starting BMI for that study was 27 – which is well below the average Weight Watchers participant. So in order to achieve goal weight the average lifetime member probably had to lose less than 10 lbs and would have to include a lot of people who had even less to lose.
So we’re not talking about massive weight loss here. And what about maintenance? The study spins it this way: of these successful losers, “weight regain from 1 to 5 y following weight loss ranged between 31.5 and 76.5%. At 5 y, 19.4% were within 5 lb of goal weight, 42.6% maintained a loss of 5% or more, 18.8% maintained a loss of 10% or more, and 70.3% were below initial weight.” He concludes that these results “suggest that the long-term prognosis for weight maintenance among individuals who reach goal weight in at least one commercial program is better than that suggested by existing research.”
That’s sounds promising. But actually, wait. Some of those numbers aren’t too impressive on second glance, e.g. that 20% staying within 5 lb of goal weight is kind of meaningless – since we don’t know how many of them were within 5 lb in the first place. That 76% of weight lost is regained isn’t too impressive either, considering they didn’t have that much to lose to begin with.
And what about the number we’re really looking for – how many people actually become “normal” weight long-term using Weight Watchers? It turns out only 3.9% of the golden 6% were still at or below goal weight after 5 years. By my calculations that means 3.9%*6.3% = 0.24% or about two out of a thousand Weight Watchers participants who reached goal weight stayed there for more than five years.
Two in a thousand? I hear you cry. That doesn’t sound so bad! I’m a disciplined person! I can be one of two in a thousand!
Maybe. But remember, not only are you competing with people that have to keep off two pounds. There’s also this: there are innumerable medical conditions that cause weight loss weight loss and wasting including cancer, drug abuse, thyroid problem and AIDS. (I started listing them in my head and had to stop because I completely lost track of the topic.) It’s reasonable to expect that at least two in a thousand Weight Watchers members fall into one of these categories and was going to lose a lot of weight regardless. This is why you do controlled studies to determine the efficacy of a treatment, you know – to adjust for all those people who were going to get better (or in this case lose weight) anyway.
In fact the combined annual incidence rate of medical conditions that can cause significant weight loss far exceeds two in a thousand by orders of magnitude. I would actually have predicted far more “successful losers” in a random population just from a back of the envelope calculation.
Which makes me wonder: how the hell are the Weight Watchers dieters (excuse me “lifestyle changers”) so successfully avoiding weight loss? What’s their trick?
Science or Not?
Now what I’ve just done. Is this any relationship to science? Picked out the most damning numbers in a slightly less successful study to paint a dismal portrait of Weight Watchers? Of course it’s not science. And I could have pointed out that the most successful 6% did manage to keep off a few pounds on average after five years. I could have mentioned that the 2007 study claimed a 16% goal weight maintenance after five years – of which I’m skeptical – but which would have translated to ten in a thousand instead of two in a thousand Weight Watchers members (woohoo). I could have conceded that some of the Weight Watchers members who didn’t achieve their goal weight might have come close.
But why should I feel obligated to do that when weight loss researchers – including this one – aren’t engaged in anything remotely related to science either. And when they feel no compulsion to be honest or transparent, selectively culling data to play up the faintest glimmers of hope, and downplay the overwhelmingly negative evidence — purely to promote a treatment that is wildly unsuccessful. And leading millions to believe that if we’re fat we can be thin. Because unless we’re extremely lucky – lottery lucky – we can’t.
There’s This Thing Called Informed Consent
But mainly I just raised the bar for “weight loss success” to the level that most people have in mind when they start a weight loss program. I don’t feel the least bit apologetic about this, because weight loss industry advocates for decades have been quietly lowering the bar further and further down so that by now their definition of “a successful weight loss program” bears little relation to what the ordinary person would think it means.
When you hear diet drug claims that they “double” weight loss – it’s probably true – they probably had a study where their 2 lb weight loss doubled the average of 1 lb weight loss.
Which is why a popular topic for weight loss researchers to write about these days is whether “unrealistic weight loss expectations” matter. This is code for “should we feel guilty about the fact that when we talk about ‘success’ we’ve come to mean something completely different from what the public’s been duped into thinking we mean?”
I have a two-word answer: informed consent.
(By the way, if anyone wants a good review of the data out there on weight loss programs I suggest UCLA’s study.)
Update: Oops, blew it. I looked at my notes again and the lifetime membership was 189,000 not 100,000. Which means that Weight Watchers had a whole 2 out of a thousand success rate. My bad. Now don’t all stampede to Weight Watchers, people. One at a time.
Update 2: Numbers in the article fixed.