Calories Made Combustibly Simple

Calories Made Combustibly Simple

David Katz 02/08/2019 2

The recently published CALERIE trial should sound the death knell of every fad diet that ever was, is, or would be (it won't, of course). The study showed, in the proverbial nutshell, that calorie restriction, per se, causes weight loss in the overweight, which in turn causes an array of improvements in the customary measures of cardiometabolic risk. 

You can get more details on the study if you like, but I’m inclined to leave it there. Replace the prevailing, utterly rule-free “see food” diet (i.e., I see food, and I eat it…) with any set of rules - all carbs; no carbs; nothing but cabbage soup; nothing but grapefruit; only this with only that; ketogenic, macrobiotic, Dukan, HCG, or any cockamamie nonsense you like - and in the short term, you will wind up restricting choice and calories, losing weight, and because of weight loss, looking transiently like you’ve improved your health, too, without meaningfully or sustainably doing so.

Shall I tell you what I really think? Maybe next time.

Then, there’s the calories underlying all this, the subject of intense and frequent fascination, preoccupation, doubt, debate, and – well- perpetual nincompoopery. As promised, I want to make this topic combustibly simple, and then once and for all- strike a match to it.

1) Calories, per se, are like the Volume of Fuel in a Fuel Tank

I trust you will agree that the volume of gasoline, assuming that is the relevant fuel (as, alas, it still is far too often), matters to what your car can do. More fuel, other things being equal, means more miles to drive. Gas gauges in cars would not measure the changing volume of fuel if it didn’t matter; gas gauges at gas stations wouldn’t do so either; and you would not pay more, or less, depending on the number of gallons (or, for our friends elsewhere in the world, liters) you determined to pump.

But gauges do measure volume, and dollars do flow with it- because quantity so obviously does matter. More fuel, more energy, more driving. Period, no debate, that’s it, that’s all- thanks for dropping by.

2) The Kind of Fuel you Put in the Tank is like your Diet

Whoever decided that if calories “count,” then the quality of food choice cannot, deserves to be pelted senseless (note: that wouldn’t require much pelting, because they are obviously devoid of any sense at the start! Just wanted to be clear I was not advocating any violence…) with the multicolored marshmallows that are part of every American child’s complete breakfast. What absurd, contrived, flagrant nonsense.

If the calories you consume are like the volume of gasoline in a fuel tank, then the composition of your diet is like the composition of that fuel. Obviously, blatantly, the importance of gallons does nothing to denounce the importance of: what kind of fuel?

The same gallons of gasoline or vinegar, water or…grape jelly…would, I trust we agree, evoke very different responses from your car. In the case of the fabulously complex human body, exactly the same is true, only more so.

The quality of fuel will alter how well a car runs on however many gallons of that fuel; so, too, the human body on however many calories. The quality of fuel will change how far a car runs on any given volume; so, too, the human body on any given number of calories. 

You would never think that if the gallons matter, then it can’t possibly matter whether the gas is regular, plus, or super; it can’t matter if it’s clean, contaminated, diluted with water, or delivered entirely as the pulverized dust of Doritos or donuts- and yet when it comes to our bodies, we talk ourselves into exactly such patent silliness. Stop.

3) Your Body is like the Car, Only More So

Are you shocked, appalled, dismayed, or hopelessly confused when I remind you that two different cars will travel different distances on the same volume of the same fuel?

No, you are not. You are entirely familiar, and completely comfortable, with the notion of fuel efficiency.  We measure it; it’s on constant display as MPGs, or miles per gallon.

You know that a more fuel-efficient car will travel further on any given amount of any given fuel than a less efficient car.  The stupefying mystery of this arcane phenomenon is not a topic of constant, breathless conjecture; you will not see it parsed into competing theories on morning shows or in best-selling books offering mutually exclusive insights. We can sum it all up in a single word (if it even qualifies as a word): DUH! Of course a more fuel-efficient car is more fuel efficient. That does not refute the relevance of fuel volume (gallons), or fuel type (quality)- it is just ALSO true.

And there’s more. The same car will run more or less well, further or less far, on the same volume of the same fuel based on…other aspects of its overall condition. Under-inflated tires, clogged filters, or degradation of circulating fluids (e.g., oil)- will all change the interactions of a car, fuel volume, and fuel quality. So, too, for the human body and food.

And, even as weight change itself can change the interaction of a body and the calories that sustain it, so can changing the load of a car alter its fuel efficiency. Load your car with rocks, and you will see that much more fuel is required to travel the same distance. The human body is rather the same: larger, heavier bodies (i.e., you before weight loss) need more calories to function the same as smaller, lighter bodies (i.e., you after weight loss).

One final analogy: higher quality fuel can reduce the volume of fuel required for a car to go a certain distance. For you, higher quality food choices can reduce the calories required to fill you up to satisfaction, and nourish you fully. Clean, high quality fuel for a vehicle, in other words, is like nutrient-dense, wholesome food for you.


So, yes, it’s true- the calorie is the stored energy required to raise the temperature of one cubic centimeter of water one degree Celsius at sea level. Yes, a kilocalorie is the energy required to do the same to a liter. Yes, it’s true, the calorie has been studied in calorimeters, and calorimeters are not human bodies.

It’s all true, and: so what? Do you know or care about the ignition temperature of the fuel in your car? Do you know or care about force generation, piston displacement, or the torque conversion ratio of your vehicle’s fuel combustion? More importantly: do you need to know or care about any of this to understand that the volume of gasoline in your tank, the quality of that fuel, and the overall condition of your car- all matter to your journey?

You do not. Take a match accordingly to every distracting argument you’ve ever heard about calories; blow up every abstruse, recondite, pseudo-intellectual digression. Calories = gallons; diet quality = fuel caliber; your body = the vehicle.

Calories are relevant to right-sizing your diet, but while calories count, there are far more productive approaches than counting them incessantly. Aim for a high diet qualitycomprised of high-quality foods to minimize the calories required to feel full and satisfied, and to optimize the overall performance of the one vehicle you can never replace. And take good care of that vehicle in every other way possible, too.

Calories do count, and are combustibly simple. If I may borrow some closing brashness from Rihanna: now, shut up and drive.

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  • Liam McArthur

    Food is so much more than calories.

  • Jack Grundy

    We need vitamins and minerals in our diet. Without them, our bodies break down.

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David Katz

Healthcare Expert

David L. Katz, MD, MPH, FACPM, FACP, FACLM, is the Founding Director (1998) of Yale University’s Yale-Griffin Prevention Research Center, and former President of the American College of Lifestyle Medicine. He has published roughly 200 scientific articles and textbook chapters, and 15 books to date, including multiple editions of leading textbooks in both preventive medicine, and nutrition. He has made important contributions in the areas of lifestyle interventions for health promotion; nutrient profiling; behavior modification; holistic care; and evidence-based medicine. David earned his BA degree from Dartmouth College (1984); his MD from the Albert Einstein College of Medicine (1988); and his MPH from the Yale University School of Public Health (1993). He completed sequential residency training in Internal Medicine, and Preventive Medicine/Public Health. He is a two-time diplomate of the American Board of Internal Medicine, and a board-certified specialist in Preventive Medicine/Public Health. He has received two Honorary Doctorates.

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