Whether or not you agree with the policy, New York Mayor Michael Bloomberg’s big soda ban is big news. Last week, he proposed to ban the sale of sugared drinks larger than 16 oz. in restaurants, movie theaters, and a variety of other venues, effective March 2013. This is one of many bold moves his administration has made to stem the obesity epidemic in New York, including a requirement to post calorie counts and a ban on artificial trans fats. (And historically, NYC’s public health efforts have worked–bringing its life expectancy well ahead of the national average.) But this proposal is the first of its kind in the nation, and it’s safe to say that other major cities are watching.
Bloomberg’s proposal has a firm foundation in research showing that limiting portion size does indeed limit consumption. Several academic studies that have shown that caloric intake decreases when you do something as simple as making portions smaller.
And sodas are an easy target; they have no positive nutritional value and are packed with sugar and calories. Even with ice, a 44-oz. Super Big Gulp can have as many as 512 calories, all from sugar (that Big Mac, by comparison, has 550, some of which come from protein and are good for you). Mega-doses of refined sugar, like those you get in sodas, have clearly been linked to Type II diabetes in multiple studies. Unlike Type I diabetes, which can happen to anyone and requires the insulin supplementation we commonly associate with diabetics, Type II diabetes is acquired later in life, often the direct result of an unhealthy lifestyle, and only requires insulin supplementation in severe cases. But even Type II diabetes decreases life expectancy by 5-10 years on average.
So how do I feel about Bloomberg’s proposal? Well, to form an opinion, I need to see if the policy works. Which is much easier said than done. And honestly, it’s a question that hasn’t often been asked until recently. This NYT editorial shows how, traditionally, policies have been built on rather tenuous ground—much like our approach to medicine:
Without evidence, we rely on anecdote, ideology or faith. That’s the way things were done before the Enlightenment, when bloodletting was believed to cure everything from acne to epilepsy. But science moves slowly. What we consider scientific evaluation today (i.e., treatment and control groups and random-assignments) is actually relatively new. The first randomized study of a medication, streptomycin, was published in 1948, and it was only in 1962… that the government began requiring pharmaceutical companies to demonstrate “substantial evidence of effectiveness” of drugs. Only in recent decades has evidence-based medicine emerged as an important movement in health care, challenging the idea that the doctor always knows best… Baseball diehards will recognize the parallels to sabermetrics and Billy Beane’s “moneyball.”
Social policy has been mainly on the sidelines of this movement… Under presidents Reagan and Clinton, there were several notable randomized studies that examined welfare reform policies. However, by and large, rigorous evidence has been used sporadically by governments.
But isn’t there evidence for the big soda ban? Didn’t I mention studies linking portion control to reduced caloric intake? Indeed I did—but that’s not the type of evidence I’m looking for, because it doesn’t measure the right outcomes. If Bloomberg’s goal was to reduce the amount of soda consumed in one sitting at fast food joint, he’ll probably succeed. But if his goal is (as I hope) to improve the health of New York, I’m not so sure.
Soda calories consumed in one sitting is what researchers call an “intermediate outcome”—a measure that doesn’t capture what is ultimately of interest. An equivalent in medicine would be using someone’s blood pressure as an indicator of heart health, rather than one’s overall risk of heart attacks, strokes, etc. It might sound trivial, but shifting from intermediate outcomes to ultimate outcomes has actually led to substantial changes in treatment guidelines for conditions as common as high blood pressure.
In the case of Bloomberg’s policy, measuring the ultimate outcome will be much harder. First, we’d have to find a sufficiently similar “control” population that we’d compare New York to, because soda consumption might already be on the decline because of other factors (increased public education, etc., come to mind). With a well-chosen control and enough data, we’d be able to see the law’s spillover effects—for example, would it lead people to buy two 16-oz. soda cups and double-fist? Would they buy more bottles in stores? Next, and perhaps more challenging, we’d have to track the health of both populations long enough for the soda ban to bear fruit, and to ensure the law doesn’t get repealed before it shows any real results. Even then, I find it hard to believe that shrinking sodas will change what we’re really interested in: people’s weight, hospitalization rates, healthcare costs, and the like.
But I’d love to be proven wrong.
Wrong or right, though, I think Bloomberg’s proposal has value as a policy experiment. If it does work, I think we’ll see many more governments follow suit; if it doesn’t, we’ve gained valuable knowledge about the types of public health initiatives that succeed in fighting obesity.
The use of evidence to drive medicine is actually a fairly new phenomenon, and perhaps unsurprisingly, the use of evidence in social policy is even newer. A large, but less widely publicized element of President Obama’s healthcare reform is a range of “waiver” opportunities for healthcare providers, states, and local governments to experiment with different approaches to lowering costs and improving healthcare, so long as they collect data to see whether or not the policies work. (A New Yorker piece by Atul Gawande shows how policy experiments led to tremendous increases in farm productivity, and hints at the potential for Obama’s waivers to achieve the same success.)
photo credit: Flickr
Karan works in strategic research on health care and will begin medical school this fall.
Follow him on Twitter @KRChhabra.