Does Calorie Counting Work? A Critical Look



If you’re confused about whether calorie counting is effective or not, then you’re definitely not alone.

Some insist that counting calories is useful because they believe losing weight boils down to the concept of calories in versus calories out.

Others believe that calorie counting is outdated, doesn’t work and often leaves people heavier than when they started. Both sides claim their ideas are supported by science, which only makes matters more confusing.

This article takes a critical look at the evidence to determine whether counting calories works.

What is a calorie?

A calorie is defined as the amount of heat energy needed to raise the temperature of one gram of water by 1°C.

Calories are normally used to describe the amount of energy your body gets from what you eat and drink.

Calories can also be used to describe the amount of energy your body needs to perform physical tasks including:

  • breathing
  • thinking
  • maintaining your heartbeat

The amount of energy provided by foods is normally recorded in thousands of calories, or kilocalories (kcal).

For instance, one carrot generally provides you with 25,000 calories, or 25 kcal. On the other hand, running on the treadmill for 30 minutes generally requires you to use 300,000 calories, or 300 kcal.

However, because “kilocalories” is an awkward word to use, people often use the term “calories” instead.

For the purposes of this article, the common term “calorie” will be used to describe kilocalories (kcal).

How does your body use calories?

If you’re wondering why calories matter, here’s a quick overview of how your body uses them.

It begins with what you eat. Food is where your body gets the calories it needs to function.

During digestion, your body breaks down the foods you eat into smaller units.

These subunits can either be used to build your own tissues or to provide your body with the energy it needs to meet its immediate needs.

The amount of energy your body gets from the subunits depends on where they come from:

  • Carbs: 4 calories per gram
  • Protein: 4 calories per gram
  • Fat: 9 calories per gram
  • Alcohol: 7 calories per gram

Your body uses the calories produced from metabolizing these nutrients to power three main processes, which are listed below (1Trusted Source2Trusted Source).

7. Basic metabolism

Your body will use most calories to perform basic functions, such as providing energy to your:

  • brain
  • kidneys
  • lungs
  • heart
  • nervous system

The amount of energy required to support these functions is referred to as your basal metabolic rate (BMR). It makes up the largest proportion of your total daily energy requirements (1Trusted Source).

6. Digestion

Your body will use part of the calories you consume to help you digest and metabolize the foods you eat.

This is known as the thermic effect of food (TEF) and varies based on the foods you eat. For instance, protein requires slightly more energy to be digested, whereas fat requires the least (3Trusted Source).

About 10–15% of the calories you get from a meal will be used to support the TEF (3Trusted Source).

5. Physical activity

The remainder of the calories you get from foods fuel your physical activity.

This includes both your everyday tasks and your workouts. Therefore, the total number of calories needed to cover this category can vary from day to day and person to person.

You need a calorie deficit to lose weight

Once your body’s immediate energy needs are met, any excess energy is stored for future use.

Some of it is stored as glycogen in your muscles, but most will be stored as fat.

Therefore, if you eat more calories than your body needs, you will gain weight, mostly from fat (4Trusted Source5Trusted Source6Trusted Source7Trusted Source8Trusted Source9Trusted Source).

On the other hand, if the calories you get from your diet are insufficient to cover your immediate needs, your body is forced to draw on its energy stores to compensate.

This is what causes you to lose weight, mostly from your body fat (10Trusted Source11Trusted Source12Trusted Source13Trusted Source).

This calorie balance concept has been proven time and time again and persists whether your calories come from carbs, fat, or protein (10Trusted Source12Trusted Source1415Trusted Source1617Trusted Source18Trusted Source).

Summary In order to lose weight, you always need to burn more calories than you eat.

Not all calories are created equal

The seemingly simple question of whether calories from fat, protein, and carbs are different is controversial, since it depends on how you look at it.

Just like inches and pounds, calories are a unit of measurement.

Therefore, purely in terms of weight loss, 100 calories will remain 100 calories regardless of whether they come from an apple or a donut.

However, in terms of health, all calories are not created equal.

It’s important to make the distinction between quantity and quality. Even foods that have the same quantity of calories can be of different nutritional quality and can have very different effects on your health (19Trusted Source20Trusted Source21Trusted Source).

Different foods tend to affect your metabolism, hormone levels, hunger, and appetite differently (22Trusted Source2324Trusted Source).

For example, eating 100 calories worth of donuts may not diminish your hunger as effectively as eating 100 calories from apples.

Therefore, a donut may make you more likely to overeat later in the day, preventing you from achieving the calorie deficit needed for weight loss.

Why it may seem like calories don’t matter for weight loss

Biologically speaking, a calorie deficit is always needed to lose weight. There’s no way around it.

Yet, many people claim that, when you’re trying to lose weight, what you eat is more important than how much you eat.

This claim is generally fueled by studies in which participants on low-carb diets appeared to lose more weight than those on high-carb diets, despite eating as many or even more total calories (25Trusted Source26Trusted Source27Trusted Source28Trusted Source).

At first glance, these studies seem to suggest that a calorie deficit is not needed for weight loss. They are often used as proof that calorie counting is useless.

However, this is a poor interpretation of the evidence for the following three reasons.

4. People are bad at estimating what they eat

Many studies rely on participant food diaries rather than direct measurements to determine how many calories they eat or burn through physical activity.

Unfortunately, food and activity journals are notorious for being highly inaccurate.

In fact, studies report that participants generally underestimate how much they eat by up to 45% and can underreport their calorie intake by as much as 2,000 calories per day.

Similarly, people tend to overestimate how much they move by up to 51%. This holds true even in cases where participants are paid to be accurate (293031Trusted Source32Trusted Source33Trusted Source).

Even dietitians fall short when they’re asked to report their calorie intake accurately, although to a lesser extent than non-nutrition professionals (34Trusted Source).

3. Low-carb diets are higher in protein and fat

Low-carb diets are, by default, higher in protein and fat, which can make you feel fuller.

This helps reduce hunger and appetite and may cause participants on low-carb diets to eat fewer total calories per day (12Trusted Source35Trusted Source36Trusted Source37Trusted Source).

Protein also requires slightly more energy to digest than carbs and fat, which can contribute to the energy deficit needed for weight loss, at least to a certain extent (3Trusted Source).

However, the slightly higher number of calories burned during protein digestion will not make a significant difference to your weight loss (1415Trusted Source38Trusted Source).

2. Studies often measure weight loss rather than fat loss

Many studies only report the total amount of weight lost, without specifying whether this weight came from loss of fat, muscle or water.

Low-carb diets are known to reduce the body’s carb stores. Since carbs are normally stored together with water in your cells, lowering your body’s carb stores inevitably leads to water weight loss (39Trusted Source).

This may make it appear as though low-carb diets help participants lose fat more quickly than they do.

1. Studies controlling for these three factors put the myth to rest

To truly settle the debate on whether calories matter for weight loss, look at evidence solely from studies that control for the above three factors.

Such studies consistently show that weight loss always results from people eating fewer calories than they expend. Whether this deficit comes from eating fewer carbs, protein, or fat makes no difference (10Trusted Source12Trusted Source1415Trusted Source1617Trusted Source18Trusted Source).

Why counting calories generally works

Counting calories is a time-tested way to lose weight.

In fact, many studies show that recording your food intake and physical activity are very effective ways to lose weight (40Trusted Source41Trusted Source42Trusted Source43Trusted Source44Trusted Source45Trusted Source).

A recent review reports that weight loss programs incorporating calorie counting led participants to lose around 7 pounds (3.3 kg) more than those that didn’t. It seems that the more consistently you do the recording, the better (46Trusted Source4748Trusted Source49Trusted Source).

For instance, one study reports that participants who monitored everything they ate for 12 weeks lost twice as much weight as those who monitored less frequently.

In comparison, those who didn’t monitor at all actually gained weight (47).

There are three reasons why calorie counting works:

  1. Tracking your calories can help you identify which eating patterns you need to modify to successfully lose weight (50Trusted Source).
  2. Despite its lack of precision, tracking what you eat can give you an approximate baseline to work from and compare to when you’re trying to reduce the total number of calories you eat per day.
  3. Finally, keeping track of what you eat can help you monitor your behavior. This may help keep you accountable for the daily choices you make and motivate you to continue progressing toward your goals.

That said, it’s important to note that calorie counting is not a requirement for weight loss (51Trusted Source52Trusted Source53Trusted Source).

What really matters is your ability to create and sustain the energy deficit needed to lose weight, even if you’re not actively aware of how the deficit is achieved.

Calorie counting is simply a tool that some may find useful.

The best ways to keep track of what you eat

If you’re interested in counting calories, there are several ways to go about it.

All involve recording what you eat, whether on paper, online, or in a mobile app.

According to studies, the method you pick doesn’t really matter, so it’s most effective to pick the one you personally prefer (54Trusted Source55Trusted Source).

Here are five of the best online calorie-counting websites and apps.

You can somewhat counteract your natural tendency to inaccurately estimate how many calories you eat by using scales and measuring cups. These can help you measure food portions more accurately.

You might also want to try using the following visual guidelines to estimate your portion sizes. They’re less accurate, but useful if you have limited access to a scale or measuring cups:

  • 1 cup: a baseball or your closed fist
  • 4 ounces (120 grams): a checkbook, or the size and thickness of your hand, including the fingers
  • 3 ounces (90 grams): a deck of cards or the size and thickness of the palm of your hand minus the fingers
  • 1.5 ounces (45 grams): a lipstick or the size of your thumb
  • 1 teaspoon (5 ml): your fingertip
  • 1 tablespoon (15 ml): three fingertips

Finally, it’s worth mentioning that counting calories only allows you to evaluate your diet from a quantity perspective. It says very little about the qualityof what you eat.

When it comes to health, 100 calories from apples will affect your health differently than 100 calories from donuts.

Therefore, avoid picking foods solely based on their calorie content. Instead, make sure you also consider their vitamin and mineral contents. You can do so by favoring whole, minimally processed foods.


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