If you ever really need proof about how the human body works, find your way into a metabolic chamber. There are about 30 of them in the world and they cost millions of dollars. They use the best technology to measure every single ounce of energy that is either consumed or burned.
These chambers allow scientists to better understand diseases that affect the human body, including things like obesity and metabolic disorders. They also definitively answer the question that’s been debated for decades: calories do matter. And, they are the primary factor that influence whether you gain or lose weight. The question is whether a “calorie is a calorie” and more about understanding why all calories are not equal.
No scheduled trips to your nearest metabolic chamber? Don’t worry. We’ll help you make sense of what foods influence your metabolism and hunger, and how you can make food work for you.
What Is A Calorie?
We often think of calories as something we eat, but, the truth is, a calorie is simply a unit of energy. More specifically, a calorie is the amount of energy required to raise the temperature of one gram of water by one degree celsius.
What does the temperature of water have to do with calories in your food? Well, scientists determine the amount of calories in a food using a technique we’re all guilty of in the kitchen: they burn it
This process is called bomb calorimetry. First, you place an ingredient in a sealed stainless steel container surrounded by water. Then, heat is applied to the food until it burns. This chemical reaction generates a ton of heat and slowly heats the surrounding water. Scientists then measure how high the temperature of the water rises to calculate the number of calories in the food.
Although accurate, this process is slowly losing favor. Today, most calories listed by the USDA and FDA are calculated in a different way. Instead of burning the food, the total amount of calories are determined by adding up the calories provided by the individual components of the food. This means determining the amount of energy from the protein, carbohydrates, fat, and alcohol.
This method works because the calories in a gram of protein, carbohydrates, fat, and alcohol remain constant. Each macronutrient has the following caloric values:
1 gram of protein = 4 calories
1 gram of carbohydrates = 4 calories
1 gram of fat = 9 calories
1 gram of alcohol = 7 calories
That’s how you add up the calories in your food. But, that’s not the entire story. As you’re about to find out, macronutrients are metabolized differently, which is why all calories are not equal. Some foods (like protein) burn more calories during digestion, and other foods (like the fiber in your carbs), affect hunger and appetite.
Understanding how to balance your diet to give you the right amount of sanity – while not letting your hunger go wild – is the key to feeling in control of your diet.
Why Calories Are Not Equal (And What It Means For Your Meals)
The confusion about calories is less about how many grams are in a particular food after it’s cooked or when it’s in a package, and more about how your body makes use of those calories once you eat and digest food.
The human body is the greatest machine ever built. You need a certain number of calories to carry out every day functions like breathing, walking, and thinking. And because your very survival depends on calories, your body processes foods differently to help fuel all of your needs.
To understand how you gain and lose weight, you need to think about energy balance, which is the old calories in vs. calories out debate. Although many things can impact energy balance, the type of calories you consume plays a large role. That’s why all calories aren’t equal.
Your daily metabolic rate is influenced by many things. The three main components are:
Basal metabolic rate (BMR): This is the amount of energy your body needs to work.
Thermic effect of food (TEF): This is the amount of energy you burn when you eat.
Exercise and activity: This is the calories you burn from movement and exercise. You can split this into different categories, such as NEAT (thins like moving around and fidgeting) and your traditional workouts.
What most people don’t realize is that 65 to 80 percent of the calories you burn every day is from your basal metabolic rate. Physical activity and the foods you eat make up the remainder of your metabolism, but that doesn’t mean they’re insignificant.
Protein, carbs, and fat are all metabolized differently. Eating 100 calories of protein is different than eating 100 calories of carbs because protein has a higher thermic effect of food (TEF).
When you eat protein, up to 30 percent of the calories can be burned. In the example above, if you ate 100 calories of protein, roughly 70 calories would hit your body because 30 calories would be burned as a result of the protein’s high TEF.
In other words, the greater the TEF, the more this will influence the “calories out” portion of the calories in minus calories out equation (because not all of those calories will end up in your body and stored). Comparatively, carbs have a TEF of just 5 to 10 percent, and fat is usually around 3 to 5 percent.
This is one reason why higher protein diets tend to be associated with weight loss and maintenance. But, it’s only part of the story.
The Domino Effect of Eating More Protein
Protein also has a domino effect on hunger that makes it a great foundation for muscle gain and weight loss.
When you eat protein you increase what’s called satiety. This means a protein-rich meal leaves you feeling fuller and desiring less food (i.e. eating fewer calories).
It’s why high-calorie (some might consider them empty calories) options like fast food or ice cream can leave you feeling hungry just a few short hours later. It’s not just the calorie count of these foods. It’s that they don’t meet your body’s needs for hunger control, so you desire more food even when your calorie intake is high. These foods are fine to have once in a while, but they make it harder to stay full.
A high-protein meal can boost the release of a hormone (ghrelin), which helps quiet your hunger and plays a role in determining how quickly your hunger returns after a meal.
When you combine all of the benefits, it’s easy to see why eating more calories from dietary protein helps create a caloric deficit. Protein burns more calories (the higher TEF) and reduces the “calorie in” portion of the equation by affecting how much you’ll eat later in the day.
Plus, giving your body the protein it needs to recover from strength training can help you build more muscle mass.
Protein isn’t the only macronutrient that helps control your hunger. Fiber, which is found in carbohydrates, is also incredibly effective at increasing fullness without adding too many calories. Most fibrous foods have low energy density, which means you can eat a lot without taking in too many calories.
Learning how to eat the foods that keep you full is a simple way to give you more flexibility. The goal with any diet isn’t too restrict – it’s to provide more freedom.
If you focus on making at least half of your plate from proteins and fiber, you’re more likely to stay full and not overeat.
That way, you still have the ability to eat other foods that aren’t as nutritious. For example, although 100 calories from chicken is different from 100 calories from a candy bar — we’re still talking about 100 calories. If the candy bar doesn’t lead to you eating 10 more candy bars, then worrying about those 100 calories is time and stress your mind and body doesn’t need.
It’s why effective diets, in general, can consist of 80 to 90 percent more nutritious foods (think vegetables, fruits, nuts, seeds, higher fiber carbs, and protein) and 10 to 20 percent of foods with fewer direct health benefits. That’s the type of balance that will deliver results and prevent burnout.