You don't have to be a mathematician to understand the connection between calories and weight loss. All you need are a few simple formulas to start on the road to weight loss. Once you have determined how calories-in and calories-out work toward weight loss, you can begin a successful, lifelong commitment to your health and weight.
Caloric Balance
Weight loss is a very simple equation that should be met with balance or a deficit. Think of your weight as a balance scale; one side is calories-in and the other is calories-out. If you want to maintain your weight, both sides must balance. If you want to lose weight, the energy that you expend must be greater than the calories you eat.
Calories and Fat
To make your caloric deficit a little more clear, you should understand the formula for calories, fat and pounds to lose each week. There are 3,500 calories in one pound of fat. The general recommended amount to lose for a safe and effective weight loss is between one and two pounds per week. Taking this into consideration, to burn 3,500 extra calories in one week, you would have to reach a caloric deficit of 500 calories per day to lose one pound; 500 calories multiplied by seven days in a week equals 3,500 calories.
Your Caloric Needs
Once you know what you need to do to lose weight and how much to cut your consumption by, you also need to know how to gauge how many calories your body needs. This is a bit of a complex equation that estimates a number known as your resting metabolic rate. This is the total amount of calories it takes your body to function for life. In other words, if you were to rest all day in bed, it's how many calories your body would use. You can use this calorie amount as a starting point. For women, the formula is 447.593 + (3.098 x height) + (9.247 x weight in kg) - (4.330 x age). For men, the equation is 88.362 + (4.799 x height) + (13.397 x weight in kg) - (5.677 x age). To convert your weight into kilograms, divide your weight in pounds by 2.2. You can even use this equation by plugging in your ideal weight and eat according to the caloric needs of your goal. To avoid doing the math, many websites have online metabolic rate calculators that do these equations for you.
Calories and Physical Activity
To calculate the calories that you burn during exercise, you must know the oxygen requirement of the activity. That is, how much oxygen your body is using to make the necessary energy for the activity. For each liter of oxygen you use, five calories are burned. For example, if you exercise using 2.4 L per minute of oxygen, multiply that by 5 calories per liter of oxygen will give you 12 calories per minute. Then, multiply that by the duration you are exercising for to figure your total calories burned. The formula looks like this: X liters of oxygen per minute x 5 calories per liter of oxygen = calories burned per minute x duration = total calories burned.
Oxygen Requirements of Walking
There is an equation to estimate the amount of oxygen you use while walking or running in order to use the above equation for your total calories burned. This equation is: oxygen use = 0.1 ml/kg/min (walking speed in meters per minute) + 3.5. For example, if you are walking at 90 meters per minute, the equation would read: oxygen use = 90 meters per minute x 0.1 + 3.5 = 3.6. To estimate your speed in meters per minute, multiply miles per hour by 26.8.
Knowing the equation for oxygen use while walking and calories burned with oxygen, you can calculate your total calories burned.
References
- Centers for Disease Control: Caloric Balance
- MayoClinic.com: Counting Calories; December 19, 2009
- "Exercise Testing and Prescription"; David C. Nieman; 2007
- "Health Fitness Instructor's Handbook"; Edward T. Howley and B. Don Franks; 2003
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