A caloric deficit is the number of calories a person has consumed minus the calories burned during a set period of time. A negative caloric deficit indicates that more calories were burned than consumed, and conversely, a positive indicates more were eaten. Daily caloric deficits are useful when attempting to lose or to gain weight.
A calorie is a unit of measure which indicates the energy required to perform a certain task. The unit calorie is a very small, so calories found on food packaging are actually kilocalories, meaning calories measured in the thousands. When eating food, and thus consuming calories, people are basically eating energy. When people eat more energy than they expend, the body stores the excess energy as fat for later use. When they expend more energy than they consume, the body goes to their fat stores and uses that energy to make up the deficit. This is how a person loses weight.
There are two ways that the body burns calories. First, it burns them at rest just by maintaining the normal functioning of the body. This measured resting rate is called a basal metabolic rate (BMR) or resting metabolic rate (RMR), and it is affected by age, height, and weight.
Secondly, the body burns calories during activity. The more a person weighs the more effort a task takes, so more calories are burned. This is why dieters often find it is harder to reach their caloric deficit goals the closer they get to their goal weights.
Although there are many online sites that provide calorie information on a plethora of foods, it is harder to obtain information on calories burned. Several types of exercise equipment will display calories burned during exercise, and many online sites have listings for the approximate calories burned during popular activities. A few sites even have relatively comprehensive lists of most daily activities, and may offer caloric deficit tracking as well. There are also devices that can be worn throughout the day which track calorie usage.
Determining an appropriate caloric deficit takes more math than just subtracting calories consumed from those burned. In order to maintain a healthy weight loss program, a person must know that it takes 3,500 calories to burn one pound. Therefore, if a person were to have a caloric deficit of 1,000 calories a day, he or she would lose approximately 2 pounds (0.9 kg) in a week.
Most experts agree that 2 pounds (0.9 kg) a week is the maximum a person can consistently lose and maintain healthy weight loss. Speedier diets which promise sometimes as much as seven pounds lost in week can cause severe health problems. When weight loss happens that quickly, the body thinks its starving, so rather than use its stored fat, it hordes the fat and begins to burn off muscle instead. Muscle mass is undesirable to lose and may even cause the heart to weaken.
