Have you ever taken heroin for a cough, or a tobacco enema for a cold? If you answered “yes,” please call 911. If you said “no,” that’s because these insane prescriptions of the 1800s have long since vanished.
Yet one theory from the same time period continues to dominate the nutrition world: all calories are equal. If you’ve ever found yourself counting calories to “be healthy,” you’re relying on the outdated science that, taken at face value, is about as likely to improve your health as blowing smoke up your ass.
A (very) brief history
The calorie was first introduced around 1820 by a Frenchman talking about heat engines. When it entered the English language in the 1860s, it was with a capital C and referred to the amount of heat needed to raise one kilogram of water from 0 to 1 degree Celsius. In the late 1800s, the US food industry adopted the Calorie as a unit for food energy, and by the mid-20th century, it was an indelible part of the nutrition landscape.
Having a soft spot for an old term is one thing, but this jumbled history as both a food energy unit and heat unit has caused problems for the way we think about nutrition. Rather than being a standardized, specific amount of energy, the calories that enter your body travel through a complex web of systems that treat them very differently, depending on their source.
Digestion takes work
While you’re technically not an engine, your body does still “burn” calories through diet-induced thermogenesis. Some calories digest really efficiently (fats and carbs), while others kind of suck at it (protein). But in this case, sucking’s not a bad thing. The less efficiently a calorie digests, the more energy you’re expending to digest it
About 25% to 30% of protein calories burn during digestion, meaning 100 calories of protein actually end up being around 75 calories in your body. Carbs and fats have a much lower rate, so 100 consumed calories end up close to 100 calories in your body. For this reason, high-protein diets have a built-in “metabolic advantage” for weight loss, since your body will burn off more calories than the same calories of fats and carbs. It explains why overweight people who try diets like Paleo or the Atkins diet tend to lose weight relatively quickly.
Your body doesn’t follow a standardized definition of “calorie”
Carbs, fats, and protein are macronutrients, but within those categories there are myriad substances that further complicate the caloric picture, and the body treats each one a little differently. Take fructose and glucose, for example. These sugars are staples of the American diet, and are quite similar (they even have the same chemical formula, C6H12O6)… until they go into your mouth. For one thing, it appears that fructose might not suppress your body’s main appetite-stimulating hormone as well as glucose, which means your brain will always want more. Fructose also causes the body to create and store fat at a higher rate than than glucose, which may help explain the rise in obesity and cardiovascular disease (ever heard of high-FRUCTOSE corn syrup?).
That’s not to say that glucose is necessarily better. Calorie for calorie, the two may appear identical, but your body doesn’t see things the same way.
Certain calories leave you hungry for more
If you’ve ever inhaled 500 calories of ice cream, you know it only takes about 30 seconds. If you’ve ever inhaled 500 calories of broccoli… wait, nobody does that. You’d have to eat more than 16 cups of it (without exploding) to hit 500 calories.
Foods that fill you up are typically packed with hunger-reducing calories from healthy carbs, protein, and fiber. Foods that leave you craving more (and disgusted with yourself) get most of their calories from sugars, fats, and refined carbs. Lacking both the physical and nutritional volume to curb hunger, these “empty calories” do little more than break down your heart and build up your weight. Since empty calorie foods are so easy to eat (and literally addictive), you will always demand satisfaction, and never get it, and you’ll destroy your health along the way.
Protein and fiber are the caloric sources fighting the good fight
Empty calories are the proverbial bull in a china shop; they tear through your digestive system and spike your blood sugar. If you’re looking for a bullfighter, turn to protein and fiber. Protein makes you full, while fiber keeps you full longer. These nutritionally dense calories digest slowly and don’t dropkick your blood sugar and brain activity like empty calories. Together, this duo can help prevent overeating and mindless snacking between meals, making you naturally leaner in the short term (without ever thinking about counting calories).
Once again, you can see why high-protein diets are so appealing to those trying to lose weight. It’s easier to feel satisfied, and it often means a shift away from sugary, processed foods that make you want to eat, and eat, and eat, to keep that blood sugar high.
Science shows that calories are a dumb standard
A 2012 study led by a Harvard researcher tested the health impacts of various diets while keeping one variable the same: calories (surprise!). Using rigorous, state-of-the-art methods (stabilized isotopes anyone?), the study examined how the quality (not quantity) of calories might influence weight loss. Even at the same caloric intake, the low-carb diet was shown to burn 300 more calories than the low-fat diet. Further health implications unique to each diet led the researchers to conclude that “all calories are not created equal.”
A separate study led by Dr. Robert Lustig drives the point home. Once again, the participants consumed the same calories, but this time, only sugar was reduced. After only nine days, virtually every aspect of the participants’ metabolic health improved (some drastically). The study concluded that it wasn’t the calories causing damage, but the sugar, and they could see differences in less than two weeks. But since you’re now a fructose/glucose expert, you could probably already guess this.
So is there any reason to track calories?
Calories certainly can have a place in health management when viewed properly. If you consume more calories than you use, you‘ll gain weight. Period.
But the fixation on calories as the be-all, end-all of weight management isn’t just wrong, it’s harmful. It’s led to industry-funded research to emphasize that exercise can counteract calories consumed, in spite of all the evidence that calorie quality matters.
Calories can come from all kinds of places, and those places are more important than the calories themselves. Maybe it’s time for an update to our nutrition labels, so that we’re not using a unit from an era when heroin was considered a cough remedy.