If your weight is on your mind, you're probably overwhelmed with calories — from checking food labels for them to counting them to figuring out how many you need to stick to in order to see the numbers on the scale budge.
And while the weight-loss concept of burning more calories than you take in each day sounds simple enough, calories are still fairly misunderstood by the average person.
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Below, we clear up five common misconceptions.
Myth 1: A Calorie Is a Calorie
A 50-calorie apple behaves the same way in the body as a 50-calorie candy bar, right? Not exactly.
The idea that "a calorie is a calorie is a calorie" doesn't capture the whole picture. According to the U.S. Department of Agriculture, one calorie equals the amount of heat required to raise the temperature of one kilogram of water one degree Celsius. Going strictly off that definition, calories are the same, but you also have to factor in the quality of the calories if you're thinking about how the food will affect your metabolism and overall health.
The most-often-cited research supporting this idea comes from a July 2007 study published in Obesity that was conducted on monkeys rather than humans. It found that monkeys that consumed trans fats gained four times more weight than monkeys that did not, despite consuming the same number of calories.
"Macronutrients and micronutrients matter with everything you eat," says Deena Adimoolam, MD, an endocrinologist and assistant professor of medicine, endocrinology, diabetes and bone disease at Mount Sinai Morningside.
That's because certain nutrients signal different things to the body. For instance, refined grains and starches are less satisfying than less-processed, higher-fiber foods and can increase hunger and calorie intake later as a result, according to a December 2011 study in The New England Journal of Medicine.
So even though the calories in an apple and a small candy bar might be equal, the foods aren't treated equally in the body.
"The components that make up the calories are sometimes more important than the calories itself," says Bansari Acharya, RDN, a registered dietitian and nutritionist.
Most of the calories in the candy bar come from added sugars, she explains. The apple, on the other hand, is part of a nutrient-rich package that comes with fiber, vitamins, minerals and phytochemicals, which may fight cancer and heart disease, according to Harvard Health Publishing.
Myth 2: You Burn Most of Your Calories Through Exercise
Going on a 30-minute run in the morning may be the most physically taxing part of your day, so you probably think that's when you burn the majority of your calories. Not so.
You actually burn the most calories over the course of the day while you're at rest — whether you're sleeping, working or sitting down for a meal. That's because the body requires a significant number of calories just to keep up with its basic functions, such as breathing, digesting and circulating blood, according to the National Academy of Sports Medicine (NASM).
This is called your resting metabolic rate (RMR). There are several factors that determine your RMR, such as genetics, age, weight and height, according to the American Council on Exercise (ACE).
There are also a couple of ways to calculate your RMR, but a 38-year-old woman who weighs 145 pounds can expect to burn approximately 1,400 calories per day outside of exercise, according to the NASM.
As for that morning run? It's still a good practice, since exercise offers a host of benefits and can keep the body burning extra calories even after cool down (a phenomenon known as excess post-exercise oxygen consumption, or EPOC), according to the ACE.
Just be realistic about how many calories you're burning during the workout. For a 155-pound person, running 3 miles at a 9-minute pace burns about 400 calories, according to Harvard Health Publishing.
Myth 3: Some Foods Have 'Negative Calories'
The idea here is that the body uses more calories to eat and digest certain foods than the foods themselves contain, leading to a calorie deficit, or a "negative-calorie food."
Unfortunately, there's no science to prove that a food actually leads to a net loss in calories, according to the Mayo Clinic. Plus, quite simply: "Every piece of food has some calorie value," Dr. Adimoolam says.
That said, it's still a good idea to load your plate with these so-called 'negative-calorie foods' since they tend to be fruits and vegetables that are part of a healthy diet anyway (think: celery, lettuce and cucumbers).
Myth 4: Burning or Cutting 3,500 Calories Makes You Lose a Pound of Fat
You may have heard that 3,500 calories equals a pound of fat — an idea that can be traced back to research from the 1950s, according to a July 2014 review in the Journal of the Academy of Nutrition and Dietetics. It's a nice and simple equation, but it doesn't quite hold up.
"This is a rule of thumb that is way overgeneralized," Acharya says. "The amount it takes for a person to lose 1 pound of fat depends upon a myriad of factors, including the person's gender, activity level, lifestyle choices and changes and current diet plan."
Additionally, "everyone has a different metabolism, and everyone has a different body composition of fat versus muscle, aka lean body mass, and these factors are just a few which help determine how quickly one will lose fat," Dr. Adimoolam says.
There's also no way to target fat cells specifically when losing weight. According to the researchers behind the July 2014 review, the first phase of weight loss mainly pulls from the body's carbohydrate and protein pool, while during the second phase, which could last for months or even years, the body turns to fat.
Another issue is that, as body mass decreases, metabolism changes and the body ends up burning fewer calories at rest.
"As you start to lose weight, your body needs fewer calories and your calorie deficit will get smaller as you continue to lose weight," Acharya says. "Many people don't factor this in when they are following a generalized 'rule' and experience disappointment when they see they are not losing weight as fast as they did in the beginning."
Myth #5: Counting Calories Is the Best Way to Lose Weight
A tried-and-true weight loss tactic is to count calories and ensure you don't exceed your calorie limit at the end of the day. There's certainly some truth here — both Acharya and Dr. Adimoolam agree calorie counting can be an effective way to lose weight.
But it's not the only way. A February 2018 JAMA study suggested that being beholden to nutritional fact labels and meticulously tracking every last calorie may not be necessary for weight loss.
The study found that people who followed a simple prescription for healthy eating — maximize vegetable intake, focus on whole foods and cut back on refined flours, trans fats and added sugar — for one year resulted in a significant amount of weight loss without ever tracking calories. The researchers looked at people who followed a low-fat diet versus a low-carb diet and found this approach worked for both groups.
What matters more is that you take an individualized approach to weight loss and consider your needs and what will work best for you, Acharya says.
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- U.S. Department of Agriculture: "What is the Difference Between Calories and Kilocalories?"
- Obesity: "Trans Fat Diet Induces Abdominal Obesity and Changes in Insulin Sensitivity in Monkeys"
- The New England Journal of Medicine: "Changes in Diet and Lifestyle and Long-Term Weight Gain in Women and Men"
- Harvard Health Publishing: "Fill Up on Phytochemicals"
- National Academy of Sports Medicine: "Resting Metabolic Rate: How to Calculate and Improve Yours"
- American Council on Exercise: "Resting Metabolic Rate: Best Ways to Measure It—And Raise It, Too"
- Harvard Health Publishing: "Calories Burned in 30 Minutes for People of Three Different Weights"
- Mayo Clinic: "We've Heard That Eating Negative-Calorie Foods Might be a Good Diet Strategy. But What Exactly are They?"
- Journal of the Academy of Nutrition and Dietetics: "Time to Correctly Predict the Amount of Weight Loss with Dieting"
- JAMA: "Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion"