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What is a Calorie?  How Many Calories Should I Eat?

The Definitive Guide to Understanding Calories and Energy Balance

Understanding what a calorie is will allow you to develop a healthy relationship with food.

Knowing how many calories to eat will help you maintain or reach weight goals, improve energy and cognitive function, optimize your metabolism, support fitness, boost performance, and more!

This article will provide a clear explanation of what a calorie is and how to identify how many calories you should eat based on your lifestyle and goals.


What is a Calorie?

A calorie is a unit of measurement.  

It measures the potential energy in food.

Energy equals power, and power lets you do things.

Many factors go into how well your body uses this energy, such as food quality, processing, micronutrients, stress, sleep, and hydration, to name a few.  We’ll cover these in subsequent articles.  

For now, let’s focus on how we get energy from food.

* To learn how a calorie is measured and a more scientific explanation of a calorie, click here or read until the end of the article *

What is Food?

What exactly is food? 

Food is technically an assortment of naturally bonded chemicals that provide nutrition to the body.  

Nutrition is the process of giving the body what it needs to sustain itself and grow.

Food is made up of nutrients.  How the chemicals are connected determines what kind of nutrient it is.  Some commonly recognizable nutrients are fats, carbohydrates, proteins, vitamins, and minerals.  

Food is divided into two main categories: macronutrients and micronutrients.  

Both of these categories deserve an article of their own, but for our purposes here, a basic understanding of their difference is all we need.


Macro means “large.”

Macronutrients are nutrients people need in large quantities to provide energy and maintain life.

Fats, carbohydrates, and proteins are the most commonly recognized macronutrients, but technically macronutrients also include water and fiber.

If you’ve ever heard people refer to “macros” in health and fitness contexts, they are almost always referring to fats, carbohydrates, and proteins.

Macronutrients provide, almost exclusively, all the energy in food.

If you recall, a calorie is a measurement of the potential energy in food, so it’s important to know that calories come from macronutrients.

We’ll talk a little more about the role of each macronutrient further in this article.


Micro means “small.”

Micronutrients are essential substances people need to consume in their diets to maintain health and proper bodily function, but in relatively small amounts.  

Micronutrients refer to vitamins and minerals.  

Vitamins and minerals facilitate the breakdown and building of other substances, open and close cells, protect your body, support your immune system, transport things in your body, help all your organs function properly, and so, so much more!

Micronutrients however are so small relative to macronutrients that they do not factor into counting calories.

Think of macronutrients as logs in a fire, and micronutrients as the matches.


Okay, one final term before we jump into how to determine how many calories you need!

Metabolism refers to the chemical reactions that occur inside your body to maintain life.

The most common metabolic process is the conversion of food into energy.

When people talk about their metabolism, they’re referring to the process of breaking down food into energy.  

Remember back in biology, chemistry or biochemistry class when you saw those balls with one or two lines between them?  Those are bonds holding electrons together, and bonds are what contain stored energy.  

The breaking of these chemical bonds releases electrons and transfers stored energy.  If you have work to do, you need calories.  If you have more calories than work to do, the calories will stick to you….yup, fat!

So, metabolism measures the rate at which energy is being converted in your body, referred to as your metabolic rate.

Energy Balance 

The concept of energy balance means the amount of energy/calories consumed is equal to the amount of energy/calories you use.

If you want to lose weight, you need to be in a caloric deficit, meaning you are using more calories than you eat.

If you want to gain weight, you need to be in a caloric surplus, meaning you are eating more calories than you use.

Metabolism goes had in hand with the concept of energy balance.  Since metabolism is the rate of chemical reactions occurring in your body, it’s directly related to the amount of chemicals, foods, passing through you. 

If you eat regularly and in amounts that are enough to replenish you and provide energy without overeating, you are in a state of energy balance.  Your body, organs, and everything are happy!

If you’re chronically in a deficit, you’ll have a compromised metabolism.  

If you regularly overeat, you’ll have a higher metabolism, but not necessarily an efficient one.   Your metabolism will rise because it has to to breakdown the food.  But if it’s overworked too often it becomes exhausted and takes away from other prats of your life, such as creativity, mood, libido, and more.  Hey, it’s gotta come from somewhere!

How Many Calories Should You Eat?

To determine how many calories you should eat, we need a few simple pieces of information:

  1. How many calories do you need to maintain your basic bodily function?
  2. How active are you?
  3. Do you exercise and if so, how much?
  4. Are you trying to maintain your weight, burn fat, add muscle, tone, or train for performance or an event?

Your Basal Metabolic Rate (BMR) refers to the amount of calories you need to maintain basic bodily functions such as regulating body temperature, respiration, cognition, etc.  Think of BMR as waking up and laying in bed all day.

Your Resting Metabolic Rate (RMR) refers to how many calories you burn at rest, factoring minor movements and activity such as fidgeting, talking, and working from a desk. RMR is slightly higher than your BMR and a more practical measure of your caloric needs, since people do not realistically live in a fasted and completely sedentary state which BMR refers to. 

Most formulas and professional nutritionists build plans based on your RMR.

Step 1 – Calculating Your Basal Metabolic Rate (BMR):

A Resting Metabolic Rate (RMR) Test, like the one we offer to the greater Washington, DC Metro Area at our Performance Center in Arlington, VA is the most accurate way to literally measure and see exactly how many calories you burn at rest.  If you live in the DC Metro area and would like to schedule a metabolic scan or nutrition consult, please visit or

If you do not have access to a metabolic test, the most commonly used and accepted formula for determining your basal metabolic rate is the Mifflin St. Jeor Equation.1

We’ll walk you through the steps below. The Mifflin st Jeor Equation is:

  • Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
  • Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5

To convert pounds (lb) to kilograms (kg), divide by 2.2.

To convert inches (in) to centimeters (cm), divide by 2.54.

For a simplified version, use the calculator below.

Step 2 – Factor in Your Activity & Exercise

If you used the calculator above, you do not need to do Step 2.  The calculator already factored this in.

Multiply your BMR by which best describes your activity level below:

  • Sedentary (BMR X 0.2) – Little or no exercise. You will burn some additional calories over and above BMR even for light activity such as watching TV, working at a desk, etc.
  • Lightly Active (BMR X 0.375) – Basic daily living (sitting, eating, walking around the office or house) and/or light exercise 1-3 days/week.
  • Moderately Active (BMR X 0.5) – Moving frequently through the day (construction work, stocking shelves, cleaning, etc.) and/or moderate exercise 3-5 days/week.
  • Very Active (BMR X 0.9) – Intense activity through the day such as manual agricultural work or competitive athletic training.

* Activity level values and descriptions courtesy of 

Alternatively, if you exercise frequently or intensely and wear an activity monitor like an

Apple Watch, FitBit, Garmin, Polar, or other device that measures calories per workout,

you may use the sedentary value and add your workouts manually for a more accurate daily

intake goal.

Your BMR x your activity level + additional exercise equals your Total Daily Energy

Expenditure (TDEE). TDEE is the number of calories you need to consume to maintain your current weight and lifestyle. 

Step 3 – Adjust Your Caloric Intake Based on Your Goal

  • Maintenance = TDEE 

Maintenance means not wanting to change your weight or body composition (fat / lean mass ratio).  The purpose here is to maintain optimal health, cognition, and energy levels for the lifestyle and activities you participate in.  

  • Performance = TDEE + Additional Calorie Expenditure From Training

Performance means you are trying to maximize your physical potential.  In order to maximize your potential, your body has to have enough energy/calories to carry out the work it needs to do.  

Not eating enough can lead to chronic fatigue, aches, injury, inadequate recovery, and simply sub-par performance.  

If you are seriously training for any event, it’s strongly encouraged that you use an activity monitor to see how many calories you burn during your training and make sure you replenish your body equally.  Distance runners, triathletes, or any athlete training for several hours most days of the week can easily burn thousands of calories per day.  Michael Phelps was reported to eat up to 10,000 calories per day when training for the Olympics in Beijing!!2

  • Cutting Weight = TDEE – 250-500 Calories (but not going under your BMR)

Cutting weight requires a deficit through diet and exercise.  

You never want to go under your BMR because this will stress your body and can actually cause weight retention or even gain! Regularly eating under your BMR can cause your body to go into “battery saving mode,” decreasing your energy, cognitive capacity, and performance. 

Worse, it effects your hormones and blood sugar levels, triggering your body to preserve calories rather than use them. Not what we want. 

500 calories/day comes out to about 1 lb of weight loss per week.  As mentioned in the beginning of the article, multiple factors go into how efficiently your body burns calories, but simply speaking, this deficit is a good starting point and typically a sustainable deficit. 

You should create any deficit through a combination of diet and activity in the form of purposeful exercise. 

  • Bulking / Adding Muscle = TDEE + 250 calories 

In order to add mass, ideally pure lean muscle, you need to be in a caloric surplus.  

Remember, calories measure the potential energy in food which is directly related to the chemicals that make up the food.  In order to grow, you need more nutrients than you use.  

In order to prevent gaining fat while adding calories, it’s important to have a balanced exercise plan and to be mindful of the quality and types of foods you eat.

Reality Check Your Goals – Be Practical 

Think about sustainability.  You want to reach your goals efficiently, but in a healthy way that lasts.  It’s better to set realistic goals that let you enjoy your life rather than a crash diet that makes you miserable that you may likely quit.  “Think long term habits versus quick hacks.”

Don’t drastically cut calories and expect to be happy.

Being very low-calorie can negatively affect your energy, mood, make you irritable, decrease your strength and recovery and make you prone to injury, among many other issues.  Most importantly, it is not sustainable!  

Don’t tell yourself you’re not allowed a single cheat day until you reach your goal when you know you have a friends birthday or wedding coming up…or 3…or 5…

Don’t tell yourself to eat 5-6 small meals per day if you know you work a 10 hour day and will only have one or two quick opportunities to eat during the day.  

Remember, you want to set yourself up for success, so think long term and set goals that are challenging but practical!

A Note on Macronutrients

From earlier in this article, we learned that macronutrients are large molecules that provide almost all the calories in food.  The three types of macronutrients have distinct characteristics which are very important to note when it comes to any goal.

Below is a short description of each macro along with recommend amounts for each of the four goals listed above.


Carbohydrates are long chains of relatively simple bonds which get converted into usable energy.  They are the easiest form of energy for your body to use and provide faster energy than fats and proteins.

FYI: Carbohydrates are often separated further into simple carbs or complex carbs. 

Simple carbs have simpler chemical structures, meaning they can be digested easily, and provide faster sources of energy. 

Complex carbs are longer chains of molecules, often containing fiber, that digest over a longer period of time, like a time-released pill.  They provide more steady energy.  

Carbs are neither good or bad.  You simply need to time them around more active times and avoid excessive quantities when sedentary.

Note: 1 gram of carbohydrate = 4 calories – Maintenance: 30-40% Cutting Weight: 25-35% Adding Lean Mass: 40-55% Performance: 45-55% of TDEE + 70-80% of any additional calories burned from longer training sessions


Fats are dense compounds with more bonds, meaning they hold more energy: calories. 

Because of their density, they take longer to digest and provide more steady energy over longer periods of time.  This is ideal for sedentary periods to prevent high and low energy fluctuations, and the main reason people started doing “Keto dieting,” a diet consisting of very high amounts of fat.

Fats also serve other biological functions in the body such as insulation and waterproofing, and make up much of your hair, nails and organs.  

Note: 1 gram of fat = 9 calories – Maintenance: 25-35% Cutting Weight: 20-40% Adding Lean Mass: 15-20% Performance: 20-30% of TDEE + 5-15% of any additional calories burned from longer training sessions


Proteins are large molecules commonly known for building muscle, but proteins also play a large role in maintaining metabolism and are involved in essentially all functions of the body.  

Proteins are responsible for most cellular processes, help build and repair tissues, carry oxygen throughout the body, help maintain pH, and many more functions throughout the body.  

Proteins are not meant to be a primary energy source, but can and are broken down for energy when needed.  

Note: 1 gram of protein = 4 calories – Maintenance: 20-25% Cutting Weight: 30-35% Adding Lean Mass: 25-35% Performance: 20-30% of TDEE + 15-20% of any additional calories burned from longer training sessions

How to Use this Information to Create a Healthy Meal Plan

In my experience as a nutritionist who has worked with hundreds of clients over the years, the single best way to create a healthy meal plan is by pre-planning.  Set aside half can hour one day to write out your meal plan.

Use an app like MyFitnessPal or Cronometer to log a few typical days based on what you usually eat. 

Most people have a few go-to breakfast items, some go to lunch spots, and some bases for dinner.  Start by logging these was your bases so you’re not starting from scratch.

See where your numbers are.  If your calories or any macros are off based on your goals, fix them.  Change serving sizes, add or remove foods.  Easy!

+/- 50-100 calories or a few grams of anything is not a problem (unless you’re cutting weight for a sporting event).  The idea is to have an awareness of what you’re eating long term, not day to day.

The key to this being beneficial is pre-planning.  Logging throughout the day is not practical for most, or even healthy.  Plus, what are you going to do at 6 PM when you realize your day is off?  Stuff yourself at night?  Get frustrated?  We don’t want that!

Be realistic.  You’ll likely go out on the weekend, for a work dinner, or for some occasion.  You should!  Enjoy life!

But, do be mindful that if you cut 500 calories per day then have a few drinks, half a pizza, dessert, and brunch over the weekend, you can easily eat those 3,000 calories you cut all week back.  You don’t want to do great all week to see no progress!  Enjoy life, go out, just be mindful of your goal to avoid frustration.  

Think of this like finances.  If you set aside money all month for your savings, then on the last day blow it on a shopping spree, it doesn’t matter that you saved the 29 days before!  

*** Please note: we do not advocate logging food regularly.  If you enjoy logging, by all means, go for it.  For many people, logging food is a stressful task and not the healthiest way to interact with food.  We’ve even seen it cause people to develop a bad relationship with food and in extreme cases, eating disorders

This being said, we encourage the thoughtful use of a logging app to pre-plan a few days.  Think of it as setting up your budget.  No one wants to count every dollar, but at some point, if you want to get serious about your finances, you have to sit down and make a budget.  Say you want to set aside 5% of your paycheck for savings, great!  Figure out what that is, then do it!  You don’t need to do it every day.  Same principle for *your diet.  Pre-plan a day or two before so there is no emotion involved.  Make simple adjustments and enjoy! **

A Note on Food Timing

Nutrient timing is a topic on it’s own. Essentially, nutrient timing comes down to giving your body certain nutrients at times the they are most needed and likely to be fully utilized. 

For example, you want more carbs around workout times since they are the primary fuel for muscles.  You don’t want to eat a ton of carbs when you’re sitting on your butt because your blood sugar will rise and your body will draw out the excess to store as fat! 

Nutrient timing is more important if you have a demanding training routine or are trying to change body composition (amount of fat and muscle).  

For general purposes, follow these guidelines:

  • Protein
    • Spread protein throughout the day in relatively equal portions 
    • Have a serving of protein immediately after exercise
    • Consider a quality plant based protein powder in a breakfast smoothie for additional protein without cholesterol, plus you’ll get 2-3 servings of fruits and vegetables!
  • Carbs
    • Include complex carbs like oats, whole grains, lentils, and quinoa in breakfast and lunch to help regulate blood sugar and hunger throughout the day
    • Avoiding having large portions of carbs during sedentary times, or close to bedtime
    • Include healthy simpler carbs like fruits in breakfast and before and after exercise
  • Fats
    • Spread fats out throughout the day
    • Avoid high fat meals immediately before and after exercise since they slow digestion
    • Consider having a higher fat diet during sedentary times or if you work a deeds most of the day (good fats, not junk!)
  • Fruits & Vegetables
    • 6-8 servings per day minimum
    • Get as much variety as you can


Understanding what a calorie is and how many you should eat I the foundation of good health.

How many calories you need is not complicated!  

It only takes a few minutes to calculate your needs and create a healthy plan that fits your life and goals.  You can still have whatever you want, just be mindful based on everything we covered!

We hope you enjoyed this article.  If you have any questions please send us a message!  We’d love to hear from you!

If you’d like to receive more useful health and fitness information written by experienced professionals, please join our email list.

If you’d like to learn more or reach results faster, schedule a free consult with one of our certified nutritionists to see how we can help!

How is a Calorie Measured, Technically?

We moved this section to the end because of it’s technical nature.  It took away from the flow of the article earlier on.

It’s important to make one technical distinction before we move on.

That between a calorie (cal) and a Calorie (Cal).

A calorie, also called a small calorie or gram calorie, is the amount of heat needed to raise the temperature of one gram of water by one degree Celsius.

A Calorie, also called a large calorie, food calorie, or kilocalorie (kcal) is widely used in nutrition and refers to the amount of heat needed to raise one thousand grams of water by one degree Celsius.

A calorie is measured using an apparatus called a bomb calorimeter.3  A bomb calorimeter is essentially a sealed combustion chamber submerged in water in an enclosure that can withstand large amounts of pressure.  Pure oxygen is fed into the combustion chamber, then ignited with an electrical fuse.  The combusting substance, food, releases gas and heat through a tube which heats the surrounding air and water the tube passes through.  The change in water temperature is used to determine the calorie content of the food.

In scientific circles, the capitalized and lower case distinction is used.   

In everyday American life, a calorie is simply referring to a kcal.  What you see on a nutrition label is actually a kcal. 

Some countries require manufacturers to write their labels in kilocalories.


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Meet the Author



I'm Bobby, a certified trainer, nutritionist, executive coach & owner of Cygma Performance. I enjoy seeing people be their best. I strive to provide clear, down to earth, science based information to help people live their best!

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