A calorie is, incontrovertibly, now and forever, a calorie. Well, a kilocalorie actually. Back to that in a minute.
Not every gallon of gasoline poured into the tank of every car produces the same travel distance. But that does not induce us to ask: Is a gallon a gallon? Of course a gallon is a gallon; it is a precise and clearly defined unit of volume not up for debate. We recognize that variation in the fuel efficiency of cars can change what happens when a gallon of fuel is burned. But it was still a gallon of fuel.
A degree on any given temperature scale is a degree. That doesn't mean every degree will FEEL the same to you or me, because we are more sensitive to temperature change in some parts of the range than others. We are unlikely to notice the difference, for instance, between 41 degrees below zero Fahrenheit and 42 degrees below zero Fahrenheit. Both are so cold, who cares? But we might well notice the difference between 67 and 68 while sitting in an office if we happen to be a bit chilly at the former and comfortable at the latter. But still, a degree is a degree.
A mile is a mile. But walking one over flat ground when well-rested feels very different from climbing one up a mountain when exhausted. But the differences have to do with our condition, terrain and altitude, not distance. A mile is a mile.
Why, then, do we keep asking, as occurred in the New York Times, if a calorie is a calorie? Of course it is. It can be nothing else.
As noted above, the measure we actually use when talking about food is the kilocalorie. A kilocalorie (Europeans use the kilojoule, by the way) is the energy required to raise the temperature of one liter of water one degree Celsius at sea level. Does it sound as if that leaves much room for debate? It is a unit of energy, no more debatable than a unit of distance, temperature, volume or velocity.
Why, then, is there a cottage industry in questioning the calorie? And why am I so adamant that this cottage industry should be shut down? I will address these questions in turn.
Questioning the calorie sells. It sells books, articles, magazines, newspapers and air time. It exploits the difficulty so many of us have with weight control, and turns it into a dumbed-down pet theory, conspiracy theory, and/or magical thinking. It offers a false promise of weight loss independent of energy balance. And since real and keep-able promises about weight loss require the actual effort involved in dealing with energy balance, false promises perennially appeal.
My adamant opposition to this industry relates to the fact that it is harmful to health--public and personal. The more time we spend debating what should not be debatable, the more time we spend with understanding, consensus, collective effort and resources diverted from where they could make a meaningful and positive difference. The more often we buy a new answer to the "Is a calorie a calorie?" question, the more time we spend mired in epidemic obesity. Those profiting from the confusion probably don't mind, but you should.
"Is a calorie a calorie?" is the wrong question, obscuring all of the right questions and diverting our attention from what matters. It also is a classic example of creating confusion rather than alleviating it, by pretending to address a deep issue that is, in fact, profoundly trivial.
Here's what I mean: You are a little bit hungry, and on two successive days you get to eat limitless amounts of one of two foods with the same exact calorie content. One tastes absolutely great, and the other tastes absolutely horrible. Do you think you will eat exactly the same amount of both?
Eating more of a food that tastes great (as in: "Betcha' can't eat just one!") is NOT an invitation to question a basic law of physics. It's obvious to the point of truly trivial. Food made to taste really good will likely goad us into eating more calories. Duh.
Another non-controversy with which the constant questioning of calories makes hay: Two people can exercise the same, and eat the same, and one will gain weight while the other does not. Doesn't this prove that a calorie is not a calorie?
Of course it doesn't! All it proves is that I am not you, and you are not me! No one ever said that any two humans burn calories with exactly the same efficiency. As noted at the start, two cars may get very different gas mileage; that does not seem to tempt us to revisit the definition of a gallon over and over. People, similarly, differ in their fuel efficiency. Some can gain weight on very few calories. That isn't fair, of course, but no one ever promised us life would be. It is not a reason to debate the calorie.
The composition of food matters, because it can influence how many calories we are inclined to eat. We tend to eat more when food tastes better. We tend to eat more when food is energy-dense. We tend to eat more based on characteristics of everything from ambient lighting to dishware, as the brilliant work of Brian Wansink reveals.
We tend to eat less, i.e., fewer calories, when food is higher in volume and lower in energy density. We tend to eat fewer calories when food is rich in fiber content. We tend to fill up on fewer calories when foods have a high "satiety index" and properties that contribute to that include, but are not limited to: high quality protein, high water content and a low glycemic load. We tend to fill up faster on foods that are simple, close to nature and free of flavorings, additives and significant quantities of added sugar and/or salt.
In other words: Some foods are better for us than others, and one of the many virtues of better-for-us foods is that they tend to help us feel full on fewer calories. This probably seems obvious if you think about just a little. And that's exactly the point. The truth about calories is too obvious to support false promises, magical thinking, or book sales. So self-proclaimed renegade geniuses keep stepping into the limelight to rediscover the deep, dark debate about a basic unit of measurement that does not exist.
There are real challenges, and maybe even conspiracies, to deal with, and we are wasting our time and resources on pseudo-debate.
There is the fact that elements in the food industry have used brain scans to determine how to engineer foods that maximize the number of calories it takes for us to feel full. When they told us "Betcha' can't eat just one," it was a very safe bet they were placing.
There is the fact that our farm bill rewards all the wrong policies, and contributes to the low cost of high-fructose corn syrup and the high cost of produce.
There is the fact that experts in marketing are earning six- and seven-figure salaries to talk your 6-year-old into preferring foods likely to propel him or her toward obesity and the early onset of chronic disease, diabetes in particular.
And there is real and growing opportunity to use genomic advances to customize variations on the theme of healthful eating that lead to fullness, and weight control, most readily for different individuals.
You want a conspiracy theory? Maybe the frequency and popularity of the calorie debate is somehow being fueled by the elements in the military industrial establishment that profit from the status quo and don't want us to ask, and answer, truly meaningful questions. Or maybe it's just the work of those with books to sell.
Either way, we are wasting our time and precious resources. Imagine all the good that would come if instead of devoting our attention, time and money to improving the fuel efficiency of cars and finding better alternatives to fossil fuel, we devoted them instead to peddling books, articles, segments and blogs on the truly deep question: Is a gallon REALLY a gallon?
Folks, I have met enough people to know I am not unique. We have common sense in common. And our common, common sense is better than this! If it isn't, my daughter who lives in Brooklyn has told me there's a nice bridge for sale there.
We are wasting our energy debating the nature of the calorie, which is, simply, and incontrovertibly, a measure of energy.
And heat. The routine diversion of attention to a controversy about this that simply does not exist generates heat, but absolutely no light.
David L. Katz, MD, FACP, MPH, FACPM, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care. He is a board certified specialist in both Internal Medicine, and Preventive Medicine/Public Health, and Associate Professor (adjunct) in Public Health Practice at the Yale University School of Medicine. He is the Director and founder (1998) of Yale University's Prevention Research Center; Director and founder of the Integrative Medicine Center at Griffin Hospital (2000) in Derby, Conn.; founder and president of the non-profit Turn the Tide Foundation; and formerly the Director of Medical Studies in Public Health at the Yale School of Medicine for eight years. This post originally appeared on his blog at The Huffington Post.