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Do Calories In Versus Calories Out Matter?

Do Calories In
Calories Out Matter?


You’ve probably heard about the importance of “calories in versus calories out” if you’ve ever tried to lose weight.

This concept is predicated on the notion that if you consume fewer calories than you expend, you would lose weight. The age-old saying “Eat less, move more”

However, some individuals believe that when it comes to weight loss and long-term health, the type of food you eat is far more important than the number of calories it contains.

The purpose of this essay is to see if the “calories in versus calories out” concept is truly important.

What exactly is the calorie-in, calorie-out model?

The “calories in versus calories out” paradigm are based on the idea that the number of calories you eat must match the number you expend in order to maintain a stable weight.

“Calories in” refers to the calories you consume from your meals, and “calories out” refers to the calories you expend.

Calorie-burning processes are divided into three categories:

  • The fundamentals of metabolism. The majority of the calories you consume from food are used to maintain essential functions like your heartbeat. This is what is known as your basal metabolic rate (BMR) 1.
  • Digestion. Digestion uses about 10–15 percent of the calories you consume. This is referred to as the thermic effect of food (TEF), and it changes depending on what you consume 2, 3.
  • Physical activity is important. The calories left over from your meals are intended to fuel your physical activity, such as exercises and everyday duties like walking, reading, and dishwashing.

Your weight will remain consistent if the number of calories you consume from food matches the number of calories you expend to maintain your metabolism, digestion, and physical activity.

As a result, the “calories in versus calories out” model is exact. To lose weight, you must consume fewer calories than you consume.

A calorie deficit is required for weight loss.

To lose weight, you must consume fewer calories than you burn on a biological level. There’s no avoiding it.

Extra calories are stored for future use once your body’s energy demands are met, some as glycogen in your muscles, but the majority as fat. As a result, consuming more calories than you burn will result in weight growth, whilst consuming fewer calories than you require will result in weight loss 4.

Some studies suggest that what you eat matters more than how much you eat, meaning that your diet’s calorie level has no bearing on weight loss. These investigations, however, are founded on a few false assumptions 5, 6, 7, 8.

Those who believe that low-carb diets help people lose weight while consuming the same (or even more) calories, for example, frequently use diet journals to estimate calorie consumption.

The trouble is that diet logs, especially when filled out by nutritionists, are frequently inaccurate 9, 10, 11.

Furthermore, some studies merely report total weight reduction without specifying whether the weight loss was due to muscle, fat, or water loss.

Varying diets have different effects on muscle and water loss, making it appear as if they are more successful for fat loss when this isn’t the case 12.

Weight reduction is always the result of a calorie shortfall, according to studies that control for these variables. This holds true whether your calories come from carbohydrates, fat, or protein.

To lose weight, you must keep your “calories in” below your “calories out.” Calories may appear to be irrelevant for weight loss due to certain reasons, however, research that controls for these factors demonstrates that weight loss always necessitates a calorie deficit 13, 14, 15, 16.

Calories in vs. calories out aren’t the only factor in one’s health.

While the “calories in vs. calories out” concept is important for weight management, not all calories are created equal in terms of health.
That’s because, regardless of calorie level, different foods have varied effects on various processes in your body.
The source of calories has a different effect on your hormones and health.

Varied meals have different effects on your hormone levels.

An excellent example is the difference in effects between glucose and fructose. These two simple sugars have the same number of calories per gramme, but they are metabolised in quite different ways by your body 18.

Insulin resistance increased blood sugar levels, and higher triglyceride and LDL (bad) cholesterol levels have been associated with a diet high in added fructose compared to a diet high in glucose 19.

Fruit, on the other hand, contains natural fructose as well as fibre and water and hence does not have the same detrimental effects.

Furthermore, the type of fat in your diet might affect your reproductive hormone levels in different ways. Diets high in polyunsaturated fats, for example, appear to be beneficial and boost fertility in healthy women 20.

Furthermore, even though both types of fats give the same number of calories per gramme, replacing saturated fats with unsaturated fats in your diet may reduce your risk of heart disease 21.

The types of food you eat have an impact on how satisfied you are.

Your nutrient intake has an impact on your appetite and fullness levels.

A 100-calorie portion of beans, for example, will satisfy your appetite considerably more effectively than a 100-calorie serving of sugar.

This is due to the fact that diets high in protein or fibre are more satisfying than foods poor in these nutrients 22, 23, 24.

Because the candy is lacking in fibre and protein, it is far more likely to cause you to overeat later in the day, lessening the chances that your “calories in” and “calories out” will match.

Similarly, fructose has a stronger effect on the hunger hormone ghrelin than glucose.

It also doesn’t excite your brain’s fullness regions in the same way that glucose does, so you won’t feel as satisfied after eating fructose as you will after eating glucose 25, 26,

This is why most processed foods that are high in fructose but low in protein or fibre make maintaining an energy balance more challenging.

Calorie sources have varying effects on your metabolism.

Distinct foods have different effects on your metabolism. Some foods, for example, take longer to digest, absorb, or metabolise than others. The thermic impact of food is the metric employed to quantify this work (TEF).

The higher the TEF, the more energy it takes to digest food. The TEF of protein is the highest, while the TEF of fat is the lowest. This means that a high-protein diet necessitates the metabolism of more calories than a low-protein diet 2, 3.

This is why it’s commonly assumed that consuming protein boosts your metabolism more than carbs or fat. However, the TEF of foods appears to have just a minor impact on your calorie balance when it comes to weight reduction 27, 28, 29.

Regardless of the number of calories in a food, it can have a varied effect on your hormones, hunger, feelings of fullness, and metabolism. As a result, not all calories are created equal when it comes to your health.

Why is nutritional density important?

The number of nutrients in a food per calorie varies a lot.

When compared to less nutrient-dense diets, nutrient-dense foods include more vitamins, minerals, and beneficial substances per gramme.

Fruits, for example, are far more nutrient-dense than doughnuts. Fruit will deliver a far higher amount of vitamins, minerals, and beneficial plant components calorie for calorie.

Vegetables, whole grains, legumes, meat, fish, poultry, dairy products, and unsalted nuts and seeds are all examples of nutrient-dense foods.

Processed foods, on the other hand, such as white spaghetti, soda, cookies, chips, ice cream, and alcohol, are said to have a poor nutrient density.

Diets high in nutrient-dense foods have been associated with a lower risk of chronic diseases including diabetes and heart disease, as well as the potential to live longer 30, 31.

The “calories in versus calories out” paradigm ignore nutrient density, which is a strong reason to doubt its usefulness in terms of your health.

Nutrient-dense foods enhance your health far more than nutrient-poor diets, calorie for calorie. The “calories in versus calories out” paradigm fail to account for this, making it less relevant to your health.


The “calories in versus calories out” concept is important for weight loss from a strictly biological standpoint.

You will lose weight only if you consume fewer calories than you burn, regardless of what you eat.

However, this model neglects to account for nutritional density, which is crucial to your health. Furthermore, different foods have varying effects on your hormones, metabolism, appetite, and feelings of fullness, all of which influence your calorie consumption.

In terms of practicality, certain foods can help you maintain a healthy weight while also improving your overall health. If you only think about calories, you can overlook the overall picture.

Calories In Versus Calories Out