Before we get into whether all calories are equal, let’s take a step back. What is a calorie after all?
The most simplistic way of looking at this is that a calorie is a unit of energy that your body burns for fuel. The caloric numbers that you see on food packages are essentially the amount of energy the product contains. If you don’t burn all of the calories, whatever you don’t burn will be stored as fat. If you lower your caloric intake, you will lose weight.
But while CICO (calories in calories out) is gaining in popularity, you must do more than simply count calories because not all calories are equal. You have to consider how your body breaks down or burns these calories.
Sure, quantity matters but so does quality. Because as delicious as it may sound, you can’t just live on wine and cheese.
Carbs vs. Fats vs. Protein Calories
Macronutrients such as carbohydrates, fats, and protein are sources of calories. Here’s the caloric breakdown for each:
- Carbohydrates (sugars and starches) provide four calories per gram
- Protein provides four calories per gram
- Fats provide nine calories per gram
And fun fact — while alcohol isn’t a macronutrient, it provides seven calories per gram.
The number of calories found in one gram of sugar (which falls into the carbohydrate bucket) is the same whether the source is a gummy bear or an apple.
But how your body responds to those different sources of calories is a different story. There is a significant difference in the way different food sources, such as gummy bears and apples, affect your appetite and overall health.
How Different Calories Impact Your Body
Thermic Effect of Food
Do we burn all calories the same way, whether it comes from a protein, fat, or carb source? No.
Different macronutrients (i.e., protein, fats, carbs) affect our metabolism differently, due to the thermic effect of food.
What is the thermic effect of food? It is the temporary increase in resting metabolic rate from food intake for processing and storing said food. So foods with a higher thermic effect will have a larger proportion of calories burned by these functions.
A previous study reports the thermic effect of the three macronutrients is as follows:
- Protein = 20 to 30% increase in resting metabolic rate
- Carbohydrates = 5 to 10% increase in resting metabolic rate
- Fat = 0 to 3% increase in resting metabolic rate
A recent systematic review on the importance of breakfast corroborates that protein has a higher thermic effect than carbohydrates or fat. Breakfasts high in protein (think veggie omelette) have a higher thermic effect than a carbohydrate-heavy meal of pancakes or a fattier alternative like bacon and sausage.
So we do NOT burn all calories the same way. Your body burns more calories from processing and storing proteins than it does other macronutrients.
Satiety is a physical feeling of fullness that prolongs the intake of more food, and it’s a big factor when it comes to understanding why all calories are not created equal.
The macronutrient source of the calories you consume impacts how long you remain satisfied between meals.
Increased fiber has also been shown to reduce appetite, however the source of said fiber is important. A 2013 review found that fiber sources such as beta-glucan (found in oats and barley), rye bran and whole-grain rye had the strongest impact as an appetite suppressant.
If you eat a 250-calorie, low-fat, refined carbohydrate snack like pretzels, you’ll likely be hungry again much sooner than if you had noshed on a similar calorie snack of nuts (fiber, protein, and fat) or a slice of whole grain bread with peanut butter (fiber, protein, and fat).
Your digestive system, or your gut, is home to trillions of bacteria that actively contribute to our immune system, and it may play a role in managing our weight, development of heart disease and other conditions. Our overall gut health is an emerging area of research and we are learning that what you eat, even in the short term, can have an impact on your gut bacteria situation.
Preliminary research suggests simple refined sugars (remember the gummy bears?) may have a negative impact on gut health by changing the concentration and function of the bacteria living there. Another study in mice found that switching from a low-fat plant based diet to a more Westernized diet (high in fat and sugar) changed the microbiome of the gut in as little as one day. More research continues to be done in this area.
Bottom line: are all calories equal? No. Do sources of calories matter? Yes. Overall, both the quantity and source-quality of these calories matter.
We don’t eat calories, we eat food. Instead of focusing solely on calorie counts, listen to your body and focus on making the most out of your food. Choose wholesome, nutrient-dense foods and make sure your eating plan is one that you can follow long term.