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What is a Calorie (and How Does it Affect Weight Loss)?

Amanda A. Kostro Miller, RD, LDN

If you have just started your weight loss program, then you may be hearing a lot about “calories.” You may have been told that you need to restrict your calories for weight loss, but what is a calorie?

If you’re confused or overwhelmed with your new weight loss program, then look no further! In this post, we aim to clarify what a calorie is, what calories do for you and how to manipulate calories to lose weight.

What is a calorie?

In the most basic sense, a calorie is 1 unit of energy. We get energy from food and our body uses that energy to fuel all sorts of bodily processes like breathing, digestion, movement, heartbeat and brain function. When you see “calories” on a food label, it tells you how much energy you can obtain from that food.

For example, 1 slice of bread may be 80 calories whereas 1 scoop of ice cream may be 150 calories. The scoop of ice cream provides more energy than the slice of bread. How many calories we eat and how we utilize that energy can make us gain, lose or maintain our weight.

Are all calories the same?

When you look at the calorie content in a variety of foods, it is easy to think that all calories (regardless of what food they come from) are the same. If only it was that simple! Here is where calories, nutrition, health and reality collide.

Different types of food give us different types of nutrition. Some foods like cakes, cookies, soda, chips and other junk food give us lots of calories without a lot of valuable nutrition to keep us healthy. Calories from these types of food are called “empty calories.”

On the other hand, foods like fruits, vegetables, whole grains, fatty fish, nuts and lean proteins give us some calories, but they also give us a lot of great nutrition (i.e. vitamins, minerals, water, fiber, healthy fats, lean protein). These types of food also have nutrients in them to keep you fuller longer (preventing you from getting hungry and eating too many calories). For more information about weight loss hacks, click here.

In general, you want your diet to consist of primarily healthy foods, so that you set yourself up for nutritious calories, better health and foods that will help curb hunger.

Calories In versus Calories Out

Everyone needs calories, or energy, in order to live. Everyone has a baseline of calories that they need to eat per day in order for their body to perform basic needs of life. This baseline calorie need is called your Basal Metabolic Rate (BMR). It is the number of calories your body needs while at rest.

Your BMR is highly dependent on weight, height, age, gender, activity level and disease state (if applicable). However, you can modify your calorie intake and calorie output by changing several behaviors. The number of calories you take in can be voluntarily modified by changing how much food and what types of food you consume. The number of calories, or energy, that you burn off can be voluntarily changed by getting more active.

In general, “calories in verses calories out” is like a balance. If you eat the same amount of calories that you burn off, your weight will likely stay the same. When you eat too many calories and you don’t burn all of them off, you gain weight (because excess calories get stored as fat in the body). On the other hand, if you consume less calories than the amount your body is burning off, you will likely lose weight.

As you can see, those who are trying to lose weight should strive to eat less calories than they are burning off in everyday life and in exercise. Now, think about this: What are your estimated calorie needs for weight loss?

How Your Healthcare Team Determines Your Calorie Needs

So, now you may be thinking about the calorie goal your healthcare team recommended for you. If all calculations are correct, then your weight loss calorie goal is less than what your body burns off from day to day (at baseline and with exercise). Again, your healthcare team personalizes your individual calorie needs based on several factors:

  • Current weight
  • Goal weight
  • Age
  • Gender
  • Body composition
  • Ability to exercise
  • Projected amount of exercise
  • Current lifestyle habits
  • Acute or chronic health conditions

Even with all of these factors considered, calorie needs may still vary from person to person. Your calorie goal is a working estimation, and may need to be adjusted for a variety of reasons:

  • Change in your health status (i.e. diseases, medications)
  • Weight loss that occurs (when you lose weight, your calorie needs may need to be decreased even further!)
  • Weight plateaus or other undesired weight changes despite making healthy changes (as in, you are actually hitting your calorie and exercise goals, and you still aren’t losing weight)
  • Your non-compliance with your weight loss program (as in, not exercising to your weekly goal or eating too many calories)
  • Too much of a calorie restriction, and you are too overwhelmed to succeed
  • Not enough of a calorie restriction, and you aren’t losing enough weight

Your Responsibility and Your Clinician’s Responsibility

All of the factors mentioned above must be taken into account both before and during your weight loss program. Even though the calorie and exercise goals are up to your clinician, it is your job to do your best to follow the recommendations.

Trying your best, being honest and being accurate about your calories in and calories out is your responsibility as the person who is trying to lose weight. It is the responsibility of your clinician to modify your weight loss program and troubleshoot as needed.

Just remember: The more honest you are about meeting your goals helps the clinician modify your program quickly and accurately. It also helps you, because you will know that you are getting the best weight loss program for your needs.