Is a calorie really just a calorie?
By Jay Wiener
Calories count. A lot. However, a calorie is not a calorie. Calories from different foods are metabolized differently, with different results. Worse, calorie counts often have little to do with the amount of calories we absorb. Dieters, diabetics, etc. are monitoring their calories based on inaccurate, obsolete information: the calorie counts and the available grams of sugar are simply wrong.
Calorie counting is a mess.
In Scientific American, Rob Dunn focuses on three issues:
Calorie Counts Are Wrong – and Not Getting Better
Counting calories seems easy. A calorie (kilocalorie to purists) is a measurement of heat: it is the amount of heat required to raise one kilogram of water (2.2 lbs.) by one degree Celsius (1.8 degrees Fahrenheit.) Fats provide approximately nine calories per gram, alcohol has seven, and carbohydrates and proteins deliver just four. Every nutrition label, every diet book, and every fitness tracker rely on these numbers, which were developed in 1896 by American chemist Wilbur Olin Atwater.
However, Atwater was trying to estimate the average number of calories in one gram of fat, protein, and carbohydrates, not in actual foods. The problem: no two foods are the same, they are all digested differently. Think about corn oil and corn. If you sprinkle corn oil on a salad, then 100% of that oil will be available to your body as soon as it hits your small intestines, and little work will be required to digest it.
Now, think about an ear of corn. There’s some oil and a lot of carbohydrate in each kernel, but both require processing Your teeth chew and mash the kernels, your stomach grinds and breaks up the mash with powerful acids, enzymes, etc., and then your intestines take over. It will be many hours before the last nutrients are extracted, and even then many kernels will remain intact after they are eliminated.
It is possible to estimate the calories in the corn oil in a salad, but impossible to estimate the calories available to different people from the same ear of corn.
Calorie Counting: A Riddle Wrapped in a Mystery Inside an EnigmaAnd it gets worse. Young plants have relatively thin cell walls, so breaking them down during digestion is easy. However, older plants have sturdier cell walls and are harder to digest. The result: we extract fewer net calories from older plants than from young ones.
There’s no way to estimate the age of the different fruits, vegetables, and grains that we buy and no way to estimate how our bodies will digest them. As a result, there’s no way to accurately estimate how many calories we will absorb from them, or how many calories we use to digest them.
Calorie counts are at best estimates. And now it gets complicated.
Your body is unique. It has a unique digestive process and a unique collection of gut bacteria. If you and I were given identical portions of a food, we would extract a different net amount of calories. In the case of pure sugar or pure oil, the differences would be slight. We would both extract most of the available calories.
However, real food is very different from pure sugar and pure oil. If you and I were given identical meals of wild venison and a salad with seeds and nuts, our bodies would react very differently. Venison is tough and stringy; seeds have hard cellulose shells designed to pass through the intestines intact so that they can sprout in a friendly pile of dung. Venison, seeds, and nuts all require a great deal of chewing, an hour or so of mashing in the stomach’s acid bath, and then more hours of processing in the small intestines, where natural enzymes and gut bacteria break down the mash into digestible components. Our bodies are different; our digestive processes will be different.
And now it gets even more complicated.
I don’t eat meat, so I don’t have healthy colonies of meat-loving bacteria. If you are a meat-eater, you do. On the other hand, my tree-hugging bugs are experts at breaking down seeds and nuts. As a result, we could eat identical plates of food but absorb very different amounts of calories and nutrients, and expend very different amounts of energy in the process. If we both ate exactly 500 calories of food, you might absorb a net of 400 calories and I might absorb 300. Or vice versa. No one knows. That’s why the calorie counters from your Fitbit or sites like www.myfitnesspal.com are only slightly better than the advice from your friendly local astrologer.
A Calorie Is Not A Calorie
So… a calorie is not a calorie. What counts is the source. Not surprisingly, this hasn’t stopped Big Food from lying about it. Here’s a quote from a book my wife and I use frequently, The Fat Chance Cookbook, by Dr. Robert Lustig and my friend, Chef Cindy Gershen:
“The Coca-Cola Company’s 2013 video “Coming together” states, “Beating obesity will take action from all of us, based on one simple common-sense fact: all calories count, no matter where they come from, including Coca-Cola and everything else with calories…” In other words, “A calorie is a calorie.”
“This is just not true.”
Lustig and Gershen nail it: Coca Cola (and all sugary drinks) provide a textbook definition of empty calories. Sodas and sports drinks have sugar, an assortment of artificial additives, and sometimes a sprinkling of micro-nutrients to impress health nuts with two-digit IQs. They do not have nutritive value, so if someone drinks 1,500 calories of Coke every day (easy to do) he will still need additional 2,000+ calories from real food with real nutrients, and all those empty Coke calories will make him fat and diabetic.
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