If you are confused about whether calorie counting is effective
or not, then you are definitely not alone.
Some insist that counting calories is useful because they
believe losing weight boils down to the concept of calories
in vs 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Others believe that calorie counting is outdated, doesn’t work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.
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 and 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).
Bottom Line: Calories are used to describe
the energy your body gets from foods or expends on various
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
These subunits can either be used to build your own tissues or
to provide your body with the energy it needs to meet its
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.
1. Basic Metabolism
Your body will use most calories to perform basic functions,
such as providing energy to your brain, kidneys, lungs, heart
and 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
Your body will use part of the calories you consume to help you
digest and metabolize the foods you eat.
About 10–15% of the calories you get from a meal will be used
to support the TEF (3).
3. Physical Activity
The remainder of the calories you get from foods fuel your
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.
Bottom Line: Your body gets calories from
the foods you eat and uses them to fuel basal metabolic rate,
digestion and physical activity.
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.
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.
Bottom Line: 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
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 (19, 20, 21).
For example, eating 100 calories worth of donuts may not
diminish your hunger as effectively as eating 100 calories from
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.
Bottom Line: If you’re just looking at
whether you’ll lose weight, a calorie is a calorie and you’ll
need to consume fewer calories than you burn. But in terms of
health, not all calories are created equal.
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
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 (25, 26, 27, 28).
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.
1. 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
Even dietitians fall short when they’re asked to report their
calorie intake accurately, although to a lesser extent than
non-nutrition professionals (34).
2. 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 more full.
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 (3).
3. 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
weight loss (39).
This may make it appear as though low-carb diets help
participants lose fat more quickly than they do.
Studies Controlling for These Three Factors Put the Myth to
To truly settle the debate on whether calories matter for
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 (10, 12, 14, 15, 16, 17, 18).
Bottom Line: Certain factors help explain
why calories can seem irrelevant to weight loss. However,
studies controlling for these factors consistently show that
a calorie deficit is needed.
Why Counting Calories Generally Works
Counting calories is a time-tested way to lose weight.
One 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
(46, 47, 48, 49).
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
There are three reasons why calorie counting works:
- Tracking your calories can help you identify which eating
patterns you need to modify to successfully lose weight
- 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.
- 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
towards your goals.
What really matters is your ability to create and sustain the
energy deficit needed to lose weight, even if you are not
actively aware of how the deficit is achieved.
Calorie counting is simply a tool that some may find useful.
Bottom Line: Counting calories can help you
lose weight by giving you an overview of what you eat each
day. This can help you identify eating patterns to modify,
keeping you on track to reach your goals.
The Best Ways to Keep Track of What You Eat
If you’re interested in counting calories, there are several ways to go
All involve recording what you eat, whether on paper, online or
in a mobile app.
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
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
- 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
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 quality of
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
Bottom Line: To count your calories most
accurately, use a food journal combined with scales or
Take Home Message
The only way to lose weight is to eat
fewer calories than you burn.
Some people are able to do this without actually counting
calories. Others find that counting calories is an effective
way to consciously create and maintain this deficit.
Those interested in giving calorie counting a try should keep
in mind that not all calories are the same.
Therefore, make sure to build your menu around minimally
processed, nutrient-rich foods and don’t base your food
choices on calories alone.