Weight management is all about balancing the calories you consume and the calories you burn. Calories are the energy in food, and your body needs them to perform normal bodily functions. If you eat more calories than your body burns, your weight will increase. To determine how many calories your body normally burns, you must determine your basal and active metabolic rates, which take into account your current weight.
Basal Metabolic Rate
Your basal metabolic rate, or BMR, is the number of calories your body uses to carry out basic functions such as breathing, circulating blood, adjusting hormone levels and growing and repairing cells. By determining what your BMR is, you can discover how many calories your body needs just to exist, as your BMR does not take into account any moving, walking or exercise you do in a day. Since calculating your BMR is a somewhat complicated process, there are many online tools that can do it for you. Your BMR accounts for about 60 to 75 percent of the total number of calories you burn in a day.
Factors Affecting BMR
One of the main factors that determine your BMR is your weight. Those with a higher weight have a higher BMR, because it takes more calories for your body to perform normal processes. You may weigh more if you are tall or muscular. This link between BMR and weight means that women, who are usually smaller and weigh less than men, have lower BMRs. Your BMR also decreases as you age and lose muscle mass, as muscle causes your body to burn more calories than fat. Although many of these factors are due to genetics, you can increase your BMR by building lean muscle and losing fat. The remaining 25 to 40 percent of the calories you burn in a day are due to physical activity, reflected in your active metabolic rate.
Active Metabolic Rate
Your active metabolic rate, or AMR, takes into account not only your BMR, but also the calories you burn during digestion and food processing, as well as those due to movement and exercise. Food processing accounts for about 10 percent of the calories your body burns each day, with physical activity accounting for the remaining 15 to 30 percent. You can raise your AMR through increasing your physical activity. For example, a 30-year-old male who is 6 feet tall, 190 lbs. and not very active has a BMR of 1,965 and an AMR of 2,358. This means that this man needs 2,358 calories in a day to maintain his weight. If this same male became active, his BMR would stay the same, but the number of calories he needs to maintain his weight increases to 2,751.
Calories and Weight
Once you know your AMR, and know how many calories your body burns in a day, you can adjust your eating to meet your weight goals. If you are looking to lose weight, you must burn more calories than you consume. You need to burn 3,500 calories more than you consume to lose 1 pound. For example, a 500-calorie-per-day deficit leads to 1 pound of weight loss a week. If you are looking to gain weight, you must consume more calories than you burn. And of course, those simply looking to stay at their current weight should be consuming roughly the same number of calories they are burning.
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