I had jury duty this week. So perhaps it's a day in court that has me in the mood not only for the truth and nothing but the truth, but the whole truth about food. In this mood, I support posting calories on menu boards, but don't feel it goes nearly far enough.
You doubtless recall that school yard brain teaser: which weighs more, a pound of feathers or a pound of iron? And you no doubt recall the answer. But what about the follow-up question: which would you rather drop on your foot?
Weight is not the only relevant metric, clearly. Just ask the broken toe.
So too with food, where calories count, but they are far from all that matters. Calories tell a truth about food, but nothing remotely like the WHOLE truth. This is an important consideration as mandatory calorie labeling expands from chain restaurants to other venues, such as theatres and airplanes.
For instance, let's consider two orders of french fries. One is small and, say, 100 calories; the other is large and say, 350 calories. The calorie difference might encourage you to go with the smaller order. So far, so good.
But now imagine that the small order of fries was prepared in trans fat, and the large order was prepared in a healthful oil. If they are fries on the same menu board, that's unlikely, I know -- but nonetheless indicative of the fact that calories don't tell all.
Calorie counts are potentially valuable in helping you see the cost -- in calories -- of larger portions. But they tell you nothing about the return on that investment, in terms of either nutrition, or the fullness and satisfaction you are hoping to achieve. And the evidence suggests that while providing a reality check that does, at times, encourage the more moderate choice. The effect of posting calories is variable, and modest.
One likely reason for this is that people don't generally eat to fill a calorie quota, they eat to fill themselves. If you like a large burger and fries, you might order a smaller version of each with the calories on display. But you might, then, finish and still want more. So maybe you order another, or maybe you eat something else just a little while later. Calories may have gone down at the time of the initial selection, without going down for the day.
Calorie-only messages may compel people to choose smaller portions of less nutritious food. And here's one of the many problems with that: in general, less nutritious foods propagate overeating, while more nutritious foods help us fill up on fewer calories! If you reduce calories by reducing portion, but not by improving nutrition, there's a good chance you'll be hungry again soon, and back in line to buy more calories. Wholesome, highly nutritious foods are at times high in calories -- walnuts are an example -- but they tend to induce a lasting feeling of fullness that helps control total calorie intake in the end.
A very small order of fries -- or for that matter a small soda -- might well have fewer calories than a serving of grilled salmon, or walnuts, or avocado. That doesn't make the soda a better choice. The soda adds calories, and no valuable nutrients. The ratio of nutrients to calories in salmon, walnuts and avocado is very, very high. Yes, there are calories, but if that is your investment, there is a large return.
My view is that information about how much food you eat -- the calories -- cannot be a replacement for information about WHAT food you are eating, namely its overall quality. Eating foods of greater overall nutritional quality will make every calorie count, and help you fill up on fewer calories. I know this not just because I live this way, but because I have written not fewer than three books that extensively address the issue of nutrition and satiety: "The Way to Eat," "The Flavor Full Diet" and the two editions of my textbook, "Nutrition in Clinical Practice."
There is a saying that when you have a hammer, the world can look like a nail. Perhaps so -- and maybe I think a summary measure of overall nutritional quality is so valuable because I happen to have a very good one, NuVal. But I tend to think of NuVal just the other way around: nails were protruding everywhere, and a hammer was needed, so a group of us dedicated to public health built one.
My ideal would be menu boards that list both calories, and a NuVal score (1 to 100; the higher the number, the more nutritious the dish). That way, you could see at a glance that there are larger and smaller portions of higher and lower quality foods. Two dishes might have the same calories, but vary widely in nutritional quality; or vice versa. Were a food laced with arsenic, it would, I trust, provide scant comfort to know that your serving were a mere 200 calories. Trans fat, certain saturated fats, excess sugar and excess sodium are less potent, but more prevalent toxins than arsenic -- and similar thinking should apply.
Calories alone tell you only about quantity -- like weighing feathers and iron and letting the comparison end there. Calories can tell you how to eat less. A summary measure of overall nutritional quality can tell you how to eat better.
So, fresh from jury duty, I weigh in for doing more than just weighing feathers, or for that matter, french fries. What you drop on your foot, or put in your mouth, matters. I support posting calories. (For those who oppose it, by the way, I simply note that no one can, or wants to, take away your liberty to ignore information!) But along with this truth about food, I would also like to see something closer to the whole truth -- or else risk poorly informed, and half-baked decisions.
Follow David Katz, M.D. on Twitter: www.twitter.com/DrDavidKatz