Body weight depends on the balance between the calories you take in and the calories you burn to stay alive and to manage your everyday activities. Therefore, if you want to maintain or reduce your current weight, you need to understand your own individual energy needs. This requires a few calculations, but after that you will be less vulnerable to autonomously overeating which can lead to unexpected weight gain.
Step 1
Calculate your Basal Metabolic Rate (BMR). This is the amount of calories your body uses for its vital functions at rest. There are several equations you can use to estimate your BMR. Most of these require your current weight (W) in kilos, your height (H) in centimeters and your age (A) in years. If you are at your ideal body weight, the most accurate is the Harris-Benedict equation. The formula differs between the two genders, therefore women should input the above characteristics in the equation: BMR = 655 + (9.6 x W) + (1.8 x H) - (4.7 x A) and men in the equation BMR = 66 + (13.7 x W) + (5 x H) -- (6.8 x A). However, according to the American Dietetic Association, if you are overweight or obese, your BMR will be more accurately calculated by the Mifflin equation, which for women is BMR = (10 x W) + (6.25 x H) - (5 x A) - 161 and for men is BMR = (10 x W) + (6.25 x H) - (5 x A) + 5. Both are considered sufficiently accurate and are used in common practice for weight management.
Step 2
Estimate your physical activity level. These are extra calories that add to your total energy expenditure, depending on how much energy you spend for your daily activities, and are expressed as an activity factor. If you are following a sedentary lifestyle, such as working in an office or your car is your main means of transport, your factor should not be more than 1.2, reports the Food and Agriculture Organization. If you do light exercise one to three times per week, such as walking for half an hour, your activity level can be up to 1.4, but if you do vigorous or moderate exercise, such as running, aerobic dance, cycling for at least one hour per day, your daily activity level can increase up to 1.75, on average. If your profession demands a lot of physical activity and you exercise in your free time as well, your activity factor can reach up to 1.99.
Step 3
Multiply your activity level with your BMR, which will give you the daily amount of calories you need. For example, if your BMR is 1,450 kcal and your activity factor 1.4, you need to intake 2,030 kcal. This will be the caloric intake that will allow you to maintain your current weight. However, if you wish to lose weight you should intake less energy than the one you calculated. The American Dietetic Association provides a guide for weight loss according to which a reduction of 500 to 1,000 kcal from your daily caloric needs will lead you to a healthy weight loss of 1 to 2 lbs. per week.
Step 4
Use online tools to check your results. Several reputable websites can estimate your daily caloric needs for you. For example, the Corner University website provides the Harris-Benedict equation to calculate your BMR. The American Cancer Society also offers a calorie counter in which you only need to input your weight, your gender and your activity level. The LIVESTRONG.com The Daily Plate also gives you the chance to calculate your appropriate caloric intake, according to the specific weight goal you set.
Tips and Warnings
- To convert your imperial measurements into metric, you should be aware that 1 inch = 2.54 cm and 1 lbs. = 0.45 kilos.
- If any of the above equation variables change, you will need to adjust your daily calorie intake to them. For example, your numbers will change if you have gained or lost weight or if your levels of physical activity change.
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