There are scientific definitions for calories, but for our purposes - a calorie is a unit of measure for energy our bodies use for all vital processes. Essentially, calories = energy, energy is needed to survive. Determining how many calories you need is dependent upon on your goals. The calculations are provided below.
Total Daily Energy Expenditure Overview
Total Daily Energy Expenditure (TDEE) refers to the amount of calories used on a typical day. This value is derived using three factors:
- Resting Metabolic Rate (RMR) - The number of calories burned sustaining your vital bodily functions - pumping blood, breathing, and maintaining temperature. This accounts for about 70% of your TDEE.
- Thermic effect of food (TEF) - The number of calories burned by digesting and processing food. This accounts for about 6-10% of your TDEE.
- Energy used during physical activity - The number of calories burned while conducting any physical activity - walking, exercise, shopping - anytime you're not at rest. This accounts for about 20% of your TDEE.
Note: These percentages are for average people. Medical conditions can play a huge roll in slowing down or speeding up RMR. Also, energy used during physical activity can vary dramatically. For example, if you're training for an Iron-man, your energy expended during exercise will be drastically higher than someone who takes their dogs on a mile walk in the evening for exercise.
Estimating Total Daily Energy Expenditure
There are a number of ways to estimate your TDEE. Most of them involve multiplying your weight by an "amount of physical activity" variable.
For example (From: Fit Day):
- For sedentary people: Weight (lbs) x 14 = est cal/day
- For people who are moderately active: Weight (lbs) x 17 = est cal/day
- For active people: Weight (lbs) x 20 = est cal/day
Where did they get these "amount of physical activity" variables? These are based on the idea that your Resting Metabolic Rate (RMR), is equal to your weight (lbs) multiplied by 10. Then, your activity level (another variable) is added.
Take a 180lb man. Find his RMR: 10 x 180 = 1800 calories. He's fairly sedentary - he works in an office all day, drives home, takes his dog for a short walk, cooks dinner, and falls asleep on the couch - nearly every day. So, we'll take "Sedentary People" variable of 14. Ten of the 14 are to estimate his RMR, leaving us with four. 4 x 180 = 720 calories. So, 1800 (RMR) + 720 (Physical Activity) = 2,520 calories to maintain his current weight with his current level of activity. Or simply; 14 x 180 = 2,520 calories.
Understanding HOW these "physical activity" variables are calculated is good knowledge to have.
How accurate is this?
Two things - RMR will vary from person to person. Based on lean muscle, age, genetics, supplements, etc., some people have a higher/lower RMR than others. The variable, 10, is an average.
Second, no matter where you look or what agency puts out the "physical activity" variables, there will be slight differences. It also depends on the person performing the calculations. For example; you may think you are highly active, while realistically you're only moderately active. It's a matter of perception.
How do I get more accurate?
In order to get a more accurate description of how much physical activity you participate in, you should track your calories burned. The key here is to ensure no matter which method you use, your weight is entered accurately. Weight is one of the biggest factors in determining calories burned. These methods are not 100% perfect, but they can more accurately determine your physical activity level. This can be done a number of ways:
- GPS Watch - use while walking, running, biking, etc
- Gym Equipment - many cardio machines in the gym will calculate calories burned.
- Calorie Calculator - these will take your (weight) x (time) x (variable for activity) to calculate calories expended. Health Status offers a pretty inclusive calculator.
Applying this is easy. We'll still figure out RMR by multiplying your weight (lbs) by 10. Then add in all of the calories you've burned via physical activity. For example; 180lb man = 1,800 RMR. After work he goes to the gym where he runs for 30 minutes on the treadmill, lifts weights, and then shoots hoops for 30 minutes. Burning about 982 calories. So, 1,800 + 982 = 2,782 calories per day to maintain his current weight with that much physical activity. If he decided to forego his gym time and instead spend it on the couch, obviously, his daily maintenance calories would be less.
Now that you understand how one maintains their weight through caloric calculations, it's time to investigate losing or gaining weight.
Given these facts:
- One pound is equal to 3500 calories
- It's relatively safe to lose/gain one to two pounds per week. (This is for the average person, there are always exceptions, ie morbidly obese)
If someone wants to lose one pound a week, then they will need to restrict their weekly caloric intake by 3500 calories, or 500 calories/day (3500 calories in a pound/7 days in a week).
Let's use our 180lb male from above. He wants to lose 10lbs in 10 weeks, or one pound a week. Currently his maintenance calories are at 2,782/day, and in order to cut 3500 calories a week, we'll take away 500 calories/day for a total of 2,282 calories/day to lose one pound/week.
If he wanted to gain weight, he would do the opposite: 2,782 calories/day + 500 calories = 3,282 calories a day to gain one pound per week.
Bear in mind, as body weight decreases or increases RMR will also change; the amount of calories burned during physical activity will also change (the lighter you are, the less you have to move around, and the fewer calories you burn).
When the man reaches his goal of 170 lbs, his new RMR will be 1700, and all of his exercise will only burn 928 calories at his new weight. Meaning his new TDEE/Maintenance Calories are at 2628.
Be ready to adjust, as every body is different. Some people, if they cut 500 cal/day from their diet, they'll drop weight incredibly fast. In this case, they may only need to cut their daily caloric intake by 250. Remember, it's relatively safe to lose/gain one to two pounds per week. Or 500 cal/day may not be enough; they may need to cut/add 750 cal/day to reach the one to two pounds per week. One would need to pay attention to what is ACTUALLY happening to their body, and adjust.
Are there such things as good calories and bad calories? There are people who believe that not all calories are equal - that protein calories are not the same as carbohydrate and fat calories. For instance, fiber is a carbohydrate and technically contains 4 calories per 1 gram; however, the human body cannot digest fiber, therefore those calories do not "really" count.
These calories are so hard to count and their values are almost insignificant, so the general rule is -
A calorie is a calorie
No matter where the calorie comes from, be it carbohydrates, proteins, or fats, it's still a calorie. With this in mind, yes, one can lose weight by eating only fat. As long as the total number of calories are less than one's maintenance calories, they will lose weight. The same goes with carbohydrates and proteins.
While one can lose/gain weight eating any of the fats, carbohydrates, and proteins they want as long as they're under/over their maintenance calories, it's still a bad idea to only eat doughnuts.
Let's say our 180lb man is still trying to lose 10lbs, but he wants to do it while eating only Dunkin' Donuts' Glazed Donuts. Can he do it? Yes. One Glazed donut has 180 calories, 8g of fat, 25g of carbs, 3g of protein. Knowing he needs to consume 2,282 cal/day to lose one pound a week we'll divide that by 180 cal/donut to see how many donuts he will need to eat in a day. 2,282/180 = 12.68 donuts/day. He can eat just shy of a baker's dozen of glazed donuts per day and STILL drop a pound a week!
Of course, this is an extreme example, and it's only referring to weight loss. You'll be hard pressed to find anyone who will recommend this type of diet. Why? Because it's simply not healthy. It lacks vital nutrients, like vitamins and minerals. A human body needs a certain percentage of carbohydrates, proteins, and fats in order to function properly. Finding out one's specific percentages, based on their goals is called finding one's Nutrition Macros. This will be discussed in great detail in a later section.
To assist in counting calories it is recommended to use a program. One of the most popular programs is FitDay. They offer free and paid services as well as an outstanding PC Program that I personally use and highly recommend.
The deal with counting calories is that if you don't input your food intake right away, you will forget!
What's an empty calorie?
They are calories that come from solid fats and/or sugars that add virtually no nutrients (vitamins, minerals, etc) to the food. A few examples include soft drinks, cakes, cookies, pastries, cheese, and ice cream. Sure, they taste great, but do not provide much nutritional value.
What are Cheat Days/Meals?
Cheat days/meals are used when dieting, you forego your dietary restrictions and "pig out." They tend to be once a week based on the theory that you need to calm your emotional cravings for certain foods, as well as jump start your metabolism and provide extra energy. When consuming a lot more calories than normal, your body kicks into hyper mode in order to burn them off.