A calorie is defined as the heat required to raise the temperature of 1 gram of water 1 degree Celsius. Because this is a relatively small amount, scientists use the larger unit Calories (uppercase C), also called a kilo-calorie (abbreviated as kcal). The Calorie, or kilo-calorie, is equal to 1,000 calories. Food labels in the United States display Calories, or kilo-calories. This is all pretty technical and does not reflect typical usage in everyday language. In this book, the word “calories” refers to Calories, or kilo-calories (i.e., 1,000 calories), which is common usage. This article explains the factors that influence your daily calorie intake and shows you how to estimate the number of calories you need. Total energy expenditure (TEE) is the total number of calories your body needs on a daily basis and is determined by the following:
- Your basal metabolic rate (BMR)
- The thermic effect of food (also known as dietary-induced thermogenesis)
- The thermic effect of your physical activity
What is BMR?
Basal metabolic rate is defined as the energy required to maintain your body at rest (e.g., breathing, circulation). To precisely determine your BMR, you would need to fast from 8 to 12 hours and then undergo a laboratory test in which you sit quietly for about 30 minutes while the air you exhale is analyzed. This test determines how many calories you are burning at rest. Basal metabolic rate is 60 to 75 percent of TEE. Typically, the larger and more muscular a person is, the higher the BMR is.
What is Thermic Effect?
The thermic effect of food is the energy required to digest and absorb food. The thermic effect of food is measured similarly to BMR, although the measurement time is usually about 4 hours after you have consumed a meal. The thermic effect of food is 10 to 15 percent of your TEE. The thermic effect of activity is the amount of energy required for physical activity. It can be measured in a laboratory when you are exercising on a stationary bike or treadmill. The thermic effect of activity is the most variable of the three major components of TEE because it can be as low as 15 percent for sedentary people and as high as 80 percent for athletes who train 6 to 8 hours per day.
One other component of TEE that plays a role is non-exercise activity thermogenesis (NEAT), which is energy expended in unplanned physical activity. Recommended USDA Dietary Guidelines
Unplanned Activity and Calorie Intake
Non-exercise activity thermogenesis is characterized by any unplanned physical activity that is not exercise but is more than just sitting still. This can include taking the stairs instead of the elevator, sitting on a balance ball at your desk, parking farther from your destination in a parking lot, fidgeting, and other calorie-burning activities. By figuring out BMR, thermic effect of food, thermic effect of physical activity, and NEAT, an estimate can be made of how many total calories a person would need in a single day, or the individual’s TEE.
Although determining your energy needs in a laboratory is precise, you do not need to go to that expense to estimate the number of calories you use. Simpler yet less precise methods of estimation require first calculating your BMR based on your age, sex, height, and weight and then adding in the thermic effects of food and of activity, but this method can be rather time-consuming. For general purposes, the easiest way requires some simple math that allows you to quickly estimate your energy needs. Keep in mind that this method, although the simplest, is the least accurate and should be used only as a rough estimation. How to perform Physical Fitness Test from Home
How To Calculate Your Daily Calorie Intake?
In the above figure you can see the estimated daily calorie intake needed to maintain your current weight. To calculate your needed daily calorie intake, look at the first column, then find the activity level that best represents your current status. If you know your body weight in pounds, multiply that number by the estimated number of calories per pound in the second column; if you know your weight in kilograms, look at the third column in the table. Take a moment to do this calculation based on your body weight and activity level. Keep in mind that your final estimate is just that—an estimate. Your actual daily calorie needs may vary somewhat, but this provides an approximate starting point. To maintain your body weight, this is about how many calories you should consume. To lose or gain weight, you will need to adjust your food intake accordingly