Throw a stone in a supermarket, pharmacy, or bookstore, and you’re almost certain to hit a product that promises to make you thinner. From diets books to Health Check seals to herbal supplements, I’d wager there’s no more persuasive marketing message in the world than “Helps You Lose Weight”.
At first blush, it’s tempting to think it’s because there’s no scientific consensus on what works. Those pushing weight loss books and products certainly want you to believe that the traditional view of weight management — that calories come in by eating, get burned by activity, and that pressing either lever will affect weight — is antiquated thinking and demonstrably wrong. Indeed, you have to accept this premise if you’re going to “need” what they have to sell.
And it’s not a hard premise to accept either. After all, this “calorie math” — wherein either eating less and keep your activity level the same (diet), or eating the same and increasing your activity level (exercise) will lead to weight loss — has been around for decades, during which we’ve continued to grow more obese as a society. We all know people who’ve tried to make it work and failed. Not to mention that it’s no damn fun to put into practice.
But anecdotes and weak correlation aside, there’s another even bigger problem: the research actually does show that neither calorie restriction nor exercise are particularly good long term weight management strategies. This is an uncomfortable reality (and huge challenge) for obesity researchers, but it’s a smoking gun for the marketers of diet products, justifying the need for a new way of looking at weight loss.
Fortunately for the marketers, there’s no consensus on an alternative, so everything is fair game. On the calories-in side of the equation, most of the difference comes from the view that certain types of calories are worse than others. Public health agencies, reflecting the traditional scientific consensus, tell us that low-fat diets aid weight loss. Fans of low-carb diets like Atkins and The Zone generally dismiss this advice, choosing to demonize carbohydrates instead. Gylcemic-index diets tend to be somewhat more measured, only demonizing simple carbohydrates while venerating complex carbs that are allegedly slower to digest.
All of these approaches have heavily-touted success stories to back them up, and most of us know people in our lives that have lost weight with each of these strategies. Such anecdotes are often persuasive, yet the comparative studies have largely failed to support the claims of any of them.
For example, a large, two year study completed in 2010 that assigned 800+ overweight adults to four diets with differing levels of fat, carbohydrates and proteins, found that all four had comparable levels of weight loss — and that all participants began to regain weight after 12 months. A smaller study published in 2005 found a similar lack of differentiation between four specific diets — Atkins, Ornish, Weight Watchers, and Zone. And a 2003 systematic review found that weight loss from low-carb diets was “principally associated with decreased caloric intake and increased diet duration but not with reduced carbohydrate content.”
So does this vindicate the “old science” of calorie math? Not exactly. First, as mentioned above, while all diets provide short term weight loss, they start to wane in efficacy in the medium term and none are particularly good at long term weight loss. And second, the results on the calories-out side of the equation are also pretty dismal. A large study completed in 2009 found that while some weight loss can be expected with exercise, there were diminishing returns as exercise levels increased due to “compensatory mechanisms that attenuate weight loss.”
There is no time to explain. Let me sum up.
So the secret to weight loss is calorie math, which isn’t particularly useful for weight loss. Thanks science. Is it any wonder marketers are having a field day?
Fortunately, as skeptics we have a few more tools in our belt which — while not carrying the predictive weight of scientific consensus — can still help us make a plausible read of the situation that’s consistent with what we do know. I’m going to suggest two are relevant here.
The first is the dynamics of placebo responses. As we’ve seen with placebo treatments from homeopathy to reiki, simply doing something can have an effect. I suspect this is why most diet and exercise programs have positive results in the short term — the intervention itself causes behavioural changes that result in lower caloric intake even when that’s not the primary focus of the diet program. As time wears on, the intervention normalizes, the effect wears off, and the gains begin. In other words, it’s not the diet itself but the attention to eating that really matters. The diet is just a placebo that triggers it.
The second is the dynamics of our cognitive machinery. The cognitive sciences have demonstrated time and again that much of our decision making is automatic, and that it often takes a fair amount of cognitive effort just to recognize that, much less counteract it. Caloric regulation is so intrinsic to our survival that we’re hardly aware there’s even a regulation mechanism at all. Worse for the dieter, it was designed under conditions of caloric irregularity and often scarcity, so errs on the side of caloric accumulation in times of plenty, which is every day for most Canadians.
If the above is true — and again, I’m basing this on general skeptical principles in the absence of specific evidence, so reader beware — then weight loss is essentially a cognitive problem. The calorie math works, but our body is designed to automatically compensate for caloric reductions or higher exertion levels. In the short term we can override that automatic process through deliberate decisions about how many calories to consume and expend (i.e. diet and exercise), which may be further aided by the intervention effect of eating attentively. But keeping that weight off will require a dieter both to become permanently aware of their caloric regulation (i.e. notice themselves automatically eating more to compensate for the deliberate calorie loss), and to stop themselves from doing it.
What that means for dieters is that any tool that forces them to be aware of what they put in their mouths and its relationship to weight could have a significant impact on long term weight loss. I’d suggest that explicit weight loss goal-setting, diet diaries to track consumption and expenditure, and regular weigh-ins are probably at the top of that list. Diet books, supplements, and wonder-foods don’t even rank.
And that’s the real secret THEY don’t want you to know — losing weight may not be fun or easy, but you don’t need to take out your wallet to do it.
Photo courtesy of dno167b via Flickr under Creative Commons