Why You Can’t Rely on Calories (and What to Do Instead)
Calorie counting is central to treadmill screens, food labels, and even restaurant menus . But if you’re trying to lose weight (or just keep an eye on your healthy food), these numbers can be misleading.
You need to create a calorie deficit in order to achieve weight loss; it is clear. But the calories you regulate through diet and exercise cannot be accurately measured. You are working with estimates, not precise calculations. This 1003 calorie restaurant burger is probably in about a thousand calories, but you can’t limit yourself to those last three calories, or maybe even the last 103. Here’s why.
First, clarification. Calories are just a measure of energy in a pure physical sense: if youburn a high-calorie food like Doritos , you get more heat from it than if you burn a low-calorie food like (dehydrated) young carrots. Inside your body, the same chemical reaction occurs as in a fire: carbohydrates, fats and proteins react with oxygen to form carbon dioxide (which you breathe out) and water. Your body does this through hundreds of careful chemical reactions, and fire with fire, but at the molecular level, the idea is the same.
This is why we need to stop using phrases like “are all calories the same?” and “what matters is what calories you eat.” It’s like saying, “Here are 20 pounds of food, but what are those pounds?” Calories, like pounds, are just a measure of how much they are.
Food labels are never 100% accurate
If you’re tracking your calorie intake, you’ve probably noticed how difficult it is to count calories when you’re cooking at home. We’re also not good at serving portions ( even the experts are wrong ). But just because you have a package with a certain amount of calories does not mean that you will actually get that amount of usable energy into your body.
At the 2013 American Academy of Developmental Sciences meeting, a panel of experts pointed out many of the shortcomings in calorie counting :
[The experts] agreed that the calculation of calories for many foods is incorrect because it does not take into account the energy used to digest food; a bite that bacteria in the mouth and intestines get from various foods; or the properties of the foods themselves that speed up or slow down their passage through the intestines, such as whether they are cooked or resistant to digestion.
Cooked foods contain more calories than raw foods, which is sometimes mislabeled. The numbers on the labels come from calculations using the Atwater coefficients, developed over a century ago by comparing the energy burned with fire in food with the energy released, including feces, from people who ate that food. Unsurprisingly, food manufacturers use numbers from these studies rather than repeating experiments with each new Twinkie formula.
Processing matters too. Some of these intrepid researchers fed volunteers peanuts in various forms and found that they were unevenly digested, writing: “When eating whole nuts, 17.8% of the lipid load (in other words, fat calories) was lost in stool, while the values for peanut butter and peanut butter accounted for 7.0% and 4.5%, respectively. “
Likewise, when a group of researchers examined the calorie content of raw whole almonds, they found that the standard list for almondsoverstated the calorie content by 32% . According to nutritionist David Despain, it may be more accurate to label calories as the maximum number of calories you can get from the food rather than the exact number .
What you eat and what you burn doesn’t always add up
Of course, from a thermodynamic point of view, calories have to go somewhere. But you cannot always see or control your energy burn, and even more so to the level of one calorie.
An often repeated calculation is that 3,500 calories add up to a pound of fat, so if you eliminate that many calories from your diet (or burn the equivalent during exercise), you will lose a pound. Likewise, take 3500 and you get a pound. It’s easy on paper, but not so easy in real life. When researchers tried to get the volunteers to gain 16 pounds by feeding them an extra 1,000 calories every day for eight weeks, they ended up gaining between 3 and 15 pounds . It is clear that the extra energy has gone somewhere, obviously fidgeting (the scientific name isthermogenesis without exercise – in other words, ways of getting around when you are not intentionallyexercising ).
How you eat can also affect the amount of calories you burn by simply being yourself (technical term: resting energy expenditure ). A study published in the Journal of the American Medical Association found that people on a low-fat diet burn fewer calories at rest than people on a high-fat diet .
Digestion itself burns energy, and this seems to depend on how processed the food is and how much fiber it contains. In one delicious-sounding experiment published in Food & Nutrition Research , people who ate a fried cheese sandwich made with cheddar cheese and whole grain bread burned more calories to digest than people who ate the same white bread sandwich and singles Kraft. …
There are other places where energy can go. Studies in mice and humans, published in the journal Science , show that the microbes living in your gut can affect how much fat you store , no matter how much calories you eat.
Calorie burn estimates are not always correct.
How many calories were burned during this workout? The numbers you can find are based on weight, time and some vague activity descriptions. Yesterday’s workout and today’s workout may seem different to you, but perhaps they both fall under the weightlifting, energetic category. Or maybe “weight lifting, general.” It is not clear how to choose.
Your actual number of calories burned, of course, depends on your particular workout and your body.Some runners are more efficient than others and burn fewer calories to get the job done. This is great for them – it means they are faster or can run farther – but if you and a super-efficient runner went for a run together, you would burn different amounts of calories.
Are you doing better with a gadget that, like many fitness trackers, bases calorie burning on your heart rate? The facts show that they are better, but not perfect. A study published in the Journal of Sports Science & Medicine found that the Polar heart rate sensor (810i) and SenseWear were less accurate when rowing at lower intensity than at moderate intensity , and that the rowing machine itself was significantly lower. too high.
Another study published in the journal Medicine and Science in Sports and Exercise found that the Polar 410S provides fairly accurate calorie burn rates for men, but overestimates the calories burned by women while cycling, running and rowing by about 2 calories. in a minute. That’s a difference of 60 calories per 30-minute workout, or, in terms of food, two scones of butter or half a can of cola.
Fitness trackers claim to use multiple sensors to measure your activity, but they have a hard time detecting and calculating everything correctly . Fitbit says on its website that their device is “optimized for walking, running, and daily life and day to day life” and less suited for other activities such as cycling.
What to do instead
However, the situation is not hopeless. If you still want to create a calorie deficit (or a calorie surplus for those trying to gain weight), here’s how to take advantage of what we do and don’t know about calories:
- Let go of the idea that you can track your intake and production down to one calorie level . You just can’t.
- Make the most of food labels , but be aware that in some cases you may be getting fewer calories.
- Eat fewer processed foods, especially those with fiber, if you’re trying to cut calories . This way you can eat fewer calories and burn more for digestion.
- Continue keeping a food diary for mindfulness. This can give you an idea of how much you are eating, since the calorie count will be roughly correct (a day when you eat a dozen donuts will be more than a day when you just eat salads), and it also makes you think about what you are putting on. in the mouth. This aspect can drive some of us crazy, and unless your diet is broken, there is no need to track or fix it. It can be helpful to check your short-term food diary from time to time to make sure you are eating well, even if you don’t have the mental energy to keep track of all of your food at all times.
So, even if you may not know your calorie intake and calories burned to the last decimal place, you can still work in broad strokes to balance your diet and exercise to get what works for you. If calorie tracking helps you make better choices overall, this is a tool to use .
Photos by Paul Papadimitriou , Joe Lung , E. Dronkert and Joao Trindade .