A brief article was posted in the NY Times blogs a couple of weeks ago. It presented research that showed that calorie-postings in fast food restaurants were largely ineffective in persuading teens to lower the number of calories ordered.
And this isn't the first study to show the inefficacy of this strategy.
Despite my skepticism about over-nutrition being the de facto cause of obesity, I'm still surprised that calorie-postings did not lead to a reduction in the number of calories ordered. I would have predicted that people would order less at the particular fast food restaurant, but this would not result in an overall reduction in food consumption since a lot of food eaten at home isn't much better than that at a McDonald's or Taco Bell (two liters of soda is only a few dollars at the store). One pot won't catch all the rain through a holey roof. But this isn't why I think calorie posting are a poor strategy to combat obesity.
If you enter into the calorie counting game, you immediately begin strategizing. The macronutrients are said to contain a particular number of calories per gram. Specifically, carbohydrates = 4 kcals, protein = 4 kcals, fat = 9kcals, and alcohol = 7kcals. These are estimates derived from measuring the heat (calories) produced by combusting fixed amounts of each nutrient in a bomb calorimeter. With these measurements in mind, if your goal is to consume fewer calories, the obvious target is the calories consumed from fat. If a strategy like this can work to slim a budget, then surely it will work to slim ourselves. But it isn't so simple.
We're not metabolic black boxes; we're not remotely that simple. Case in point, endocrinologists, geneticists, and neuroscientists can all get plenty of funding to research metabolism and obesity. Something, not simply too much, is driving obesity. Robert Lustig, MD and David Ludwig MD, PhD, independently investigate this idea and describe their research as Endocrinology 101. They propose that hormones drive obesity and that the quality of our diet (particularly sugar and refined carbohydrates) is driving these hormones. Our metabolism is not analogous to a simple balance sheet.
So when presented with only calorie content, we focus on quantity rather than quality. When someone tries to eat fewer calories, he or she will reduce dietary fat and shift to a carbohydrate rich diet. Protein consumption generally stays the same. Low fat foods tend to be bland, so to preserve palatability and maintain lower calories, people tend towards refined carbohydrates - grains, flour, and sugar. Walter Willett, MD, DrPH, at the Harvard School of Public Health, has demonstrated that dietary fat is not a major contributor to obesity (http://www.ncbi.nlm.nih.gov/pubmed/12566139), and he is critical of simply replacing dietary fat (especially vegetable fats) with refined carbohydrates. This is what happened with dietary fat and heart disease (a good account of this can be read here http://civileats.com/2011/03/04/a-big-fat-debate/), and I think there is good reason to believe that calorie counting leads to a similar problem. Although perhaps to a lessor degree since sodas and candies are generally reduced with calorie-restriction.
Here's an example to illustrate my point. While it's an admittedly extreme example, I think it's a likely one. (But please keep in mind that I don't think any fast food is optimal!)
You've run out of food at home, so you decide to go to McDonald's for breakfast. You first look at the menu, and see the Big Breakfast (eggs, sausage, hash brown, regular biscuit). You don't want to eat too much, so you might skip the biscuit (or maybe not). But then you look at the Fruit and Maple Oatmeal and think: "Wow! I could cut my breakfast calories by at least 40% if I get that." But here's the break down (derived from http://nutrition.mcdonalds.com/nutritionexchange/nutritionfacts.pdf).
|Big Breakfast||Modified Big Breakfast||Fruit and Maple Oatmeal|
|Carbs from meal||27%||14%||79%|
So even if you skip the biscuit in the Big Breakfast, you can dramatically reduce the calories in your breakfast if you eat the oatmeal. Although you'll increase your carbohydrates 3-fold. And even if you keep the biscuit, you'll still have just as many carbohydrates despite the huge discrepancy in the size of the meal. Without getting into the uniquely fattening properties of starches, and sugar in particular, anyone can appreciate which meal will keep you sated longer. So while the Big Breakfast is a larger bolus of calories in one meal, it will surely do a better job of holding you until lunch without needing a snack, or sneaking one of the donuts your coworker brought into the office...