From physical movement to involuntary chemical processes, everything your body does requires calories. The body converts calories into energy, used to support all the functions of life and for survival. The number of calories you need depends on your activity level and whether you'd like to maintain your current body weight, lose weight or gain weight. Whatever your goals, calories should come from nutrient-dense foods that provide essential vitamins and minerals rather than empty junk-food calories.
What Is a Calorie?
A calorie is a unit of measurement that reflects the energy supplied by food. A calorie provides the same amount of energy whether it comes from protein, fat or carbohydrates. Technically, 1 calorie is the amount of energy used to raise the temperature of 1 g of water by 1 degree centigrade. To maintain your current weight, you need to balance your caloric intake with the calories burned to keep your body functioning -- also known as your metabolism. Your basal metabolic rate, or BMR, is the amount of energy you body needs to maintain itself. Digestion and movement are other processes that require energy.
Calculating Your Caloric Needs
Your weight and activity level are the two most important factors in determining your caloric needs. The more active you are, the more calories you need to consume. The University of Maryland Medical Center recommends you eat between 12 and 15 calories for each pound of your current body weight. A 150-lb. person would need to consume between 1,800 and 2,250 calories to maintain his current body weight. Your activity level is another determining factor, though; the University of Maryland Medical Center notes that a professional athlete might need to consume up to 25 calories per pound of body weight.
Metabolism and Weight Loss
If weight loss is your goal, eat 12 calories per pound of your ideal body weight. If you'd like to weigh 125 lb., plan to eat 1,500 calories daily. Although you can speed up weight loss by reducing your caloric intake further, you risk slowing your metabolism if you don't consume enough calories to support your BMR. If your body thinks calories are scarce, metabolism slows down to conserve energy -- it's a biological survival mechanism that allowed humans to live through harsh winters or famines, when food was hard to find. BMRs vary, but typically women need at least 1,200 calories and men need at least 1,800 calories for normal metabolic function.
Raising Your Metabolism
Your BMR uses between 50 and 80 percent of the calories you consume. Physical activities use 20 percent of your calories, and between 5 and 10 percent of your calories are used for digestion. You body can easily break down fat and carbohydrates into calories, but protein requires more work. When you eat protein, 30 percent of the calories are used simply in digestion, which may be one of the reasons high-protein diets promote weight loss. You can increase your energy requirements, burn more calories, and lose weight by increasing your activity level, building muscle mass, and eating a higher percentage of protein. Building muscle mass helps because muscle tissue uses more energy than fat, increasing your BMR.
References
- Better Health Channel: Metabolism Explained
- University of Maryland Medical Center: How Many Calories Should You Cut?
- American College of Sports Medicine: Metabolism Is Modifiable With the Right Lifestyle Changes
- Medline Plus: Diet -- Calories
- Centers for Disease Control and Prevention: Balancing Calories
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