Your body converts the calories in food to energy -- you need to eat enough to fuel your body properly, but if you eat too much those excess calories get stored as fat. Calculating the number of calories you need depends on your activity level, age, gender and current weight. The number of calories you burn is determined by your metabolism.
Calories and Metabolism
Right now, your heart is beating, you're breathing, thinking, moving and there are countless chemical processes going on in your body. These processes all use energy. Your basal metabolic rate is the the amount of calories burned just to maintain life. Between 50 and 80 percent of your calories go to your BMR. Physical activity accounts for about 20 percent of your caloric intake and digestion uses 5 to 10 percent of your calories. The higher your protein intake, the more calories burned during digestion. It's important to consume enough calories to keep your metabolism functioning; if you don't eat enough, your metabolism slows down to conserve energy, which will stop weight loss.
How Many Calories Do You Need?
The American College of Sports Medicine says that women need at least 1,200 calories and men need 1,800 calories for basic metabolic functions. The number of calories you need depends on your current weight and activity level. Sedentary people need 12 calories per lb. of body weight and moderately active people need 14 calories per lb. For example, a 140 lb. person would need between 1,680 and 1,960 calories each day. Very active may need far more than this. The University of Maryland Medical Center notes that professional athletes may need up to 25 calories per lb. of body weight.
Calories and Weight Loss
Losing weight requires you to burn more calories than you consume, without cutting calories so much that you slow your metabolism. You can create a calorie deficit by eating fewer calories and exercising to burn more energy. It takes a 3,500-calorie deficit to lose 1 lb. By eliminating 500 calories from your current daily intake, you can expect to lose 1 lb per week. The more calories you burn, the faster you'll lose weight, but remember to eat enough to keep your metabolism up. If you want to lose weight, eat 12 calories per lb. of your goal weight. If you'd like to weigh 130 lbs., eat about 1,500 calories daily.
Calorie Cutting Tips
If you're trying to lose weight, set realistic goals, such as no more than 2 lbs. per week. Eat a healthy balance of fresh fruits and vegetables, whole grains, legumes, low-fat dairy, lean protein and unsaturated fats. Practice portion control and eat smaller meals every four to five hours to avoid getting so hungry that you overeat. Don't drink your calories -- stick to water, tea, coffee and the occasional diet soda. Substitute a lower-calorie option whenever possible. For example, instead of snacking on a bag of tortilla chips, try air-popped popcorn, which has less than one third of the calories.
References
- Better Health Channel: Metabolism Explained
- University of Maryland Medical Center: How Many Calories Should I Cut?
- MayoClinic.com; Counting Calories -- Getting Back to Weight-Loss Basics; Dec. 2009;
- American College of Sports Medicine; Metabolism is Modifiable with the Right Lifestyle Chocies; March 26, 2009
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