Why Calories Do Not Matter For Weight Loss! They say “a calorie is a calorie” and I used to believe that until I became a nutrition practitioner and learned why calories do not matter for weight loss.
Focusing on a calorie number as being the most important aspect of your diet is wrong because a 100 calories of candy has a much different effect on hormones, metabolism and hunger than a 100 calories of broccoli. What makes up those calories is most important.
While it is true that all “calories” have the same amount of energy. One dietary Calorie contains 4184 Joules of energy. But when it comes to your body, it is not that simple.
Why Calories Do Not Matter For Weight Loss
The human body is a highly complicated biochemical system with complex processes that regulate energy balance. Different foods go through different metabolic pathways, some of which are inefficient and expend energy as heat (1).
More importantly, different foods and macronutrients (protein/carbohydrates/fat) have a major effect on the hormones and brain centers that control hunger and eating behavior.
The foods we eat can have a huge impact on the hormones that tell us when, what and how much to eat.
Here are 6 examples of calories that are not processed the same in the body.
Fructose vs Glucose
The two main sugars in our diet are glucose and fructose. While these sugars may seem identical (they have the same chemical formula and weigh the exact same), however in your body they are treated differentely (2).
Glucose is metabolized by all body tissues. It’s the primary form of energy the body and brain needs to function, but fructose can only be metabolized in the liver (3).
While you can eat the same number of calories of glucose as fructose, they have a very different impact on hunger, hormones and metabolism. Because your body does not treat them the same.
How glucose vs. fructose is treated different
Ghrelin is a “hunger hormone” that goes up when you’re hungry and down after you’ve eaten. One study shows that fructose consumption leads to increased ghrelin (more hunger) than glucose (4).
A high consumption of fructose can cause insulin resistance, abdominal fat gain, increased triglycerides, blood sugar and small, dense LDL compared to the exact same number of calories from glucose (5).
Keep in mind this only applies to fructose from added sugars, not the fructose from fruit. Fruits have fiber and water which slow the effects of the fructose.
Even though fructose and glucose have the same chemical formula, fructose has more negative effects on hormones, appetite and metabolism.
The Thermic Effect of Food
Different foods go through different metabolic pathways in our for your body to break them down and utilize the energy from them. Some pathways are easy for food to breakdown and others are more complicated. The more complicated the metabolic pathway, more energy is used to do that work and more energy is released as heat.
Metabolic pathways for carbs and fats are much easier than the pathway for protein. Protein has 4 calories per gram, but a large part of protein calories are lost as heat when the body breaks them down. So, you’re actually burning calories when you eat protein.
The thermic effect of food is a measure of how much different foods increase energy expenditure, due to the energy required to digest, absorb and metabolize the nutrients. Sources vary on the exact numbers, but what’s clear is that protein requires much more energy than fat and carbs (6).
This is the thermic effect of different macronutrients (7):
- Fat: 2-3%.
- Carbs: 6-8%.
- Protein: 25-30%.
If we go with a thermic effect of 25% for protein and 2% for fat, this would mean that a 100 calories of protein would end up being 75 calories, while a 100 calories of fat would end up as 98 calories.
Studies show that high protein diets boost metabolism by 80 to 100 calories per day, compared to lower protein diets (8). This is one reason why high protein is such an important component for weight loss and composition.
Protein calories are less fattening than calories from carbs and fat, because protein takes more energy to metabolize.
Protein Kills Appetite and Makes You Eat Fewer Calories
The protein story doesn’t stop at increasing your metabolism either. It significantly reduces appetite, making you eat less calories. Studies show protein is the most fulfilling macronutrient, by far (9).
If someone wanted to lose weight and only focused on increasing their protein intake, they would start losing weight without ever counting calories or controlling portions because protein automatically makes you more full and keeps blood sugar stable.
In one study, those who increased their protein intake to 30% of calories automatically started eating 441 fewer calories per day and lost 11 pounds in 12 weeks (9). This makes it very clear that when it comes to metabolism and appetite, a protein calorie is NOT the same as a carb or fat calorie.
Increased protein can lead to reduced appetite and cause automatic weight loss without the need for calorie counting or portion control.
The Satiety Index
Different foods have different effects on satiety. It’s also much easier to overeat certain foods than others. For example, it’s very easy to overeat 500 calories (or more) of chips or cookies, but if you had to overeat protein or fibers veggies it would be really hard. You would have to force feed yourself 500 calories of eggs and broccoli. This is a key example of how food choices can have a huge impact on the total calories you end up consuming.
There are many factors that determine the satiety value of different foods, which is measured on a scale called the satiety index. The satiety index is a measure of the ability of a food to reduce hunger, increase fullness and reduce hunger over several hours.
When you eat foods low on the satiety index, you will be hungrier and end up eating more. If you choose foods that are high on the satiety index, you will end up eating less. Foods with a high satiety index are boiled potatoes, beef, eggs, beans and fruits. Foods low on the satiety index include donuts, cookies, chips cake. See where this is going?
Choosing fulfilling foods has a major difference on your hunger and eating habits. The more donuts you eat, the less full you feel, therefore, you eat more.
Different foods have different effects on satiety and how many calories we end up consuming in subsequent meals and snacks. This is measured on a scale called the Satiety Index.
The Glycemic Index
One of the few things everyone agrees on in the nutrition world is that refined carbs are bad. This includes added sugars like sucrose and high fructose corn syrup, as well as refined grain products like white bread, white sugar, white flour, etc.
Refined carbohydrates are low in fiber and they get digested and absorbed quickly, leading to rapid blood sugar. They have a high glycemic index, which is a measure of how quickly foods raise blood sugar.
When you eat a food that spikes your blood sugar fast, it leads to a blood sugar crash. When your blood sugar crashes, you get cravings for more high-sugar snacks.
In one study where people were served milkshakes one group had high glycemic milkshakes while the other had low ones. The result was that the high glycemic milkshake caused increased hunger and cravings compared to the low one (10). Another study found that teenage boys ate 81% more calories during a high glycemic meal compared to a low one (11).
The speed at which a carb calorie effects your body has a dramatic effect on your cravings causing you to habitually eat more and gain weight over time. So, a 100 calories of donuts is not the same as eating a 100 calories of green vegetables.
Refined carbohydrates lead to spikes in blood sugar, which leads to increased cravings and increased food intake.
The Take Away
Different calorie sources have different effects on hunger, hormones, metabolism and the parts of the brain that control food intake. Even though calories are a component of weight, counting them does not matter for weight loss. What you fill those calories with is more important than the number. I recommend tracking macros instead of calories because it ensures you are getting the right balance of foods to reach your goals.