The dictionary definition of a “calorie” is this: it is a unit or quantity of heat that is needed to raise the temperature of 1 gram of water by 1 degree Celsius (or 1.8 degrees Fahrenheit) at atmospheric pressure.
The “calories” used in food are actually kilocalories, and 1 kilocalorie is equal to 1,000 calories. This means that if a box of cookies has 140 calories per serving — it actually means 140,000 actual calories.
Nutritionists use the word “calories” to describe the energy-producing potential in food, and it is these calories that fuel all of our bodily functions.
The “calories” in exercise also mean the same: if a fitness chart states that you will burn 100 calories for each mile that you run, it actually means you burn 100,000 calories or 100 kilocalories. Hence, when the word “calorie” is mentioned in this article or on this portal, it refers to kilocalories.
Calories have received a somewhat negative reputation in recent decades, thanks to various fad diets and the tendency to discuss calories as unwanted things. In reality, calories are essential to our survival — if we do not eat enough calories on a daily basis, our bodies will not have the energy required to continue to function, and eventually, our bodies would break down.
The important factor is knowing how many calories you are eating and how many you are burning and then making sure that you are not eating more than you are burning – this will help you avoid weight gain while maintaining a healthy lifestyle.
Breaking Down Calories in Food
The number of calories in your food shows the amount of energy that you will get from it. All foods are a combination of three building blocks, and these are carbohydrates, protein, and fat, all of which are referred to as macronutrients. The calories in each macronutrient are as follows:
- Carbohydrates – 4 calories
- Protein – 4 calories
- Fat – 9 calories
As fat has more than twice the amount of calories as carbohydrates and protein, it obviously means fat is more difficult to burn off. Therefore, it should be consumed sparingly.
Let’s take a look at the nutritional label on a box of cookies, which shows that the serving size is 25 grams, and the amount of calories per serving is 120. If we open up the packet and burn up the cookies directly in an open fire and let it burn off entirely, this will produce 120 kilocalories, which is enough to increase the temperature of 120 kilograms of water to 1 degree Celsius.
A closer look at the nutritional label will show you that there are 5 grams of fat, 16 grams of carbohydrates, and 3 grams of protein, which gives you a total of 24 grams (food companies tend to round off the amount).
Therefore, the 120 calories on the nutrition label of the cookies actually contain 45 calories from fat (5 grams multiplied by 9 calories), 64 calories from carbohydrates, and 12 calories from protein.
For the body to burn these 120 calories, it has to break down the carbohydrates into sugars, such as glucose, the proteins into amino acids, and the fats into fatty acids and glycerol. After this, these organic compounds are transferred via the bloodstream to the different cells in the body for immediate use, and the excess would be stored for future use in the form of body fat.
Sugars, proteins, and fats are each broken down by the body into different compounds, which are then used by the body for different functions. Carbohydrates are broken down by your body into glucose, which is then absorbed through the walls of the small intestine.
The glucose is processed by the liver. It then enters the body’s circulatory system, increasing the body’s blood glucose levels. This provides the body with an excellent (and quickly accessed) source of energy.
If there is excess glucose, the liver will store it to be used between mealtimes if the blood glucose levels fall below a certain level. Any glucose in excess of what the liver can store will be turned into fat to be stored for the long term.
Proteins, on the other hand, are broken down into amino acids, which are used by the body to build new proteins. Each of these proteins has a specific function, such as enabling chemical reactions or allowing cells to communicate. If the body is low in glucose and fatty acids, then the body can get energy from protein, but this is not ideal.
Finally, fat is broken down by the body into fatty acids, which are burned as energy. Fatty acids make a fantastic energy source for the body, although it is important to note that not all cells can
use fatty acids for energy — brain cells, for example, do require glucose, so be careful when thinking about limiting your carbohydrate intake. If more fatty acids are broken down than the body needs for energy at that moment, then the fatty acids are packaged together in bundles called triglycerides and then stored in fat cells for use at a later date.
Proteins, fats, and sugars each play an important role in the body, and it is essential to ensure that you are taking in enough of each so that your body has the energy and other resources that it needs to carry out all of its functions.
Our Daily Caloric Needs
When nutritional labels show the percentages of the daily values that the body needs, they typically refer to someone who follows a 2,000-calorie diet.
It is difficult to identify exactly how many calories our cells require to function properly, as each person’s daily physical activities vary, along with his or her height, weight, age, and gender.
This is why it is more helpful to look at the amount of calories listed on the nutritional label rather than the percentage of the daily diet.
To know approximately how many calories you need to consume per day so that you can achieve your weight loss goals, there are three important factors that you need to be aware of:
1. Basal Metabolic Rate or BMR
2. Physical Activity
3. Thermic Effect of Food
These three factors need to be calculated, and by adding up the calculations from these, the result would be the total amount of calories that your body requires each day.
There are many calorie counters available online, all of which give different results based on the formulas they used. Adding the above three factors is the most accurate way of determining how many calories your body requires each day.
Here’s a starting point for the number of calories you should be eating if you live a sedentary lifestyle.
For men (to maintain weight):
- Ages 19–30 should eat anywhere from 2,400 to 2,600.
- Ages 31–50 should eat anywhere from 2,200 to 2,400. Ages 51 and up should eat anywhere from 2,000 to 2,200.
For women (to maintain weight):
- Recommended 1,600 to 2,000.
Keep in mind that these are simply starting points. They will only be able to get you so far, so you will need to get an individualized number of calories to eat every day. It changes if you want to lose, gain, or maintain your weight depending on your lifestyle, which is why it is important to calculate it yourself.
Basal Metabolic Rate (BMR)
A person’s BMR refers to the amount of energy required for his or her body to function while at rest — that is to say, for the lungs to continue breathing, the heart to keep pumping, the kidneys to keep functioning, and the body temperature to remain stable.
These functions take up approximately 60 to 70 percent of the calories that are burned during the day. On average, the BMR of men is higher than that of women.
To estimate your BMR, what you can do is to follow the Harris–Benedict formula:
- For adult men: 66 + (6.3 x body weight in pounds) + (12.9 x height in inches) – (6.8 x age in years)
- For adult women: 655 + (4.3 x weight in pounds) + (4.7 x height in inches) – (4.7 x age in years)
It might look unusual for men to have 66 and for women to have 655 as the first digits in the formula, but this, in fact, is accurate.
Age is an important factor in the formula because BMR tends to decline by 1% to 2% per decade after you turn 20, largely due to continued loss of fat-free mass in the body. This is, of course, a generalization, and it can differ among individuals depending on exercise, diet, and a person’s percentage of body fat.
Increases in muscle mass will also increase your BMR, so if you have calculated your BMR previously and then started an exercise regime that has increased your muscle mass, you should recalculate to make sure that you have a current and correct idea of your BMR.
Another equation that can be used to calculate your BMR, which has been found to be approximately 5% more accurate than the Harris–Benedict formula, is the Mifflin St. Jeor Equation:
- For adult men: (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) + 5
- For adult women: (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) – 161. If you know your body fat percentage, you can also use the Katch–McArdle formula
- For adult men and women: (21.6 x fat free mass) + 370, where “fat free mass” = weight – (body fat percentage x weight)
The important thing to remember is that each individual is different, and each of these formulas will work better for some and not as well for others. If you have concerns about whether you are using the right formula, or if you are properly calculating your BMR, then you should seek your doctor’s assistance.
After BMR, this is the second main factor that burns considerable amounts of calories. This includes all that you do with your body, such as walking to work, swimming at the pool, and talking to your friend. The amount of calories that are burned off from physical activity actually depends on your body weight. The more weight you have, the more calories you actually burn off as you engage in a particular physical activity. However, if you keep eating as many calories (if not more) as you burn off, you will continue to maintain your current weight (if not increase it).
A great tool to use to calculate how many calories each activity burns is at bitelog.com/exercise- search.htm, but there are many online resources that can you help you to figure out how many calories you are burning.
While many people automatically think of activities like running or going to the gym as the best options for burning calories, there are many other activities that you can choose that will do a great job of burning calories. If you are one of those people who prefer to disguise their exercise in a fun activity, some of these options will work well for you.
Hiking and rock climbing are two excellent examples of fun, outdoor activities that will also help you to burn a large amount of calories. Depending on the difficulty of the trail and how quickly you are walking, you can burn around 400 calories per hour while hiking, whereas rock climbing can burn from 500 to 700 calories per hour. The difference in calories burned for rock climbing comes from how much you weigh because you are using your own body as the weight in this exercise. On days when the weather is not great, indoor rock climbing is always a great alternative.
If you have some household chores that need to get done and think you don’t have time to exercise, think again: those chores are exercise! Vacuuming, laundry, sweeping, and mopping will all burn calories, and using those online resources mentioned earlier can help you figure out just how many calories each chore will burn.
If you need to wash your car, that will burn about 200 calories per hour, and mowing the lawn (using a push mower, not a riding mower!) will burn around 300 calories per hour. Checking items off the “to-do list” and burning calories both make this option a great combination.
Playing sports is perhaps an obvious way to burn calories, but it still should be mentioned because it’s a great way to have fun with your friends and still get your exercise in. Football can burn around 500 calories per hour, assuming that you and your friends are somewhat serious about the game, while soccer can burn 600 calories or even more per hour. Even badminton, which is a much lower impact sport, can burn between 250 and 400 calories depending on how much you weigh.
Yoga is an excellent option because aside from burning calories (around 300 per hour), it also provides a variety of other health benefits: core strength, balance, and flexibility. Plus, it can be very soothing if you are feeling stressed out or wanting to give your body a rest from more strenuous activities.
Thermic Effect of Food
This is the last factor that burns the calories that you consume, and it is the amount of energy that the body utilizes in order to digest the food that you have consumed. After all, it does take energy to digest the foods and then break them down to the basic organic compounds that the cells need in order to function properly.
To determine the amount of calories that your body utilizes for this, what you do is multiply the total number of calories consumed within a day by 10 percent.
Exercise and Calories
When you eat a total of 3,500 more calories in a week, you will gain one pound of fat. Therefore the only way to get rid of this is by burning 3,500 calories more than what you consume in a week by reducing your portions, increasing your physical activity, or both. Burning 3,500 calories in a week will result in a 1 lb loss in body weight. It is the only way to naturally change a pound of fat into energy.
The beauty of exercise lies in its ability to boost your metabolic rate even though you have stopped doing the physical activity. Metabolism takes time to revert to its regular rate, which is why the body continues to burn calories for the next 120 minutes after exercising.
Nutrition and Calories
If weight loss was the only concern, then you would only have to count the calories. It wouldn’t matter whether it is a carbohydrate, protein, or fat calorie. But as much as you need to focus on burning more calories than what you consume, you also need to focus on the nutritional value of the foods.
Carbohydrates and proteins are better calorie sources than fats, even though the body does need fat to help absorb fat-soluble vitamins, such as vitamin A. Ideally, you should not eat foods that contain more than 25 to 30 percent of fat calories.