If only it were simple. Knowing how many calories you need to succeed with weight loss and ultimately maintenance matters! However, the most accurate determination of your caloric needs would require sophisticated equipment and complicated calculations. That’s why scientists developed simplified equations to provide you with an easier way to get a quick estimate.
Having an estimate of your calorie needs is good enough for most people. What you will want to do is determine two important values. The first one is your minimum safe caloric intake and the second is the number of calories you need to maintain your current weight. These figures give you an idea of your weight loss range.
Consuming enough calories to keep your metabolism running smoothly but fewer calories than your total needs for weight maintenance is what it takes to encourage your body to burn fat.
Minimum Caloric Needs: BMR and RMR
Even when you are resting, your body needs energy to keep your organs working and blood circulating. You also have energy needs for the growth and repair of body cells and tissues. The number of calories you need to provide this energy is influenced by body composition, gender, age, heredity, height, weight, thyroid, and activity level. This is what I covered in part one of this series on metabolism. (See: It Must Be My Metabolism: Metabolism Part One) The speed with which you burn calories for energy is referred to as basal metabolic rate (BMR) or resting metabolic rate (RMR).
BMR and RMR are not exactly the same.
In a laboratory setting the conditions under which BMR is measured provides the most precise and accurate determination of metabolic rate and calorie needs. The measurement of RMR does not require such strict conditions. Therefore the values for BMR and RMR will be close in value but not the same. For everyday purposes the two terms are often used interchangeably.
The easiest way to determine an estimate for your resting caloric needs is to use an online calculator. There are two online calculators that I use and recommend BMR calculator and Basal Metabolic Rate Calculator.
If you’d like to calculate these figures on your own you can with the Harris Benedict or Mifflin equations:
The Harris Benedict equation estimates BMR:
For women: (9.56 x w) + (1.85 x h) – (4.68 x a) + 655
For men: (13.75 x w) + (5 x h) – (6.76 x a) + 66
The Mifflin equation estimates RMR:
For women: (10 x w) + (6.25 x h) – (5 x a) – 161
For men: (10 x w) + (6.25 x h) – (5 x a) + 5
To use these equations you need to plug in the appropriate values for “w” (current weight in kg), “h” (height in cm), and “a” (age).
w = weight in kg
h = height in cm
a = age
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NOTE:
Your weight in pounds divided by 2.2 will give you your weight in kg. Multiply your height in inches by 2.54 to get your height in cm.
Keep in mind that the estimates for both BMR and RMR will be skewed (not as accurate) for anyone who has significantly more muscle mass than the average or significantly more fat than the average.
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Knowing your resting metabolic calorie needs gives you a value for your minimum safe caloric intake. To keep your metabolism from slowing down make sure you provide your body with at least this many calories from the food you eat each day. As you lose weight remember to recalculate this number because it will change.
Physical Activity
The second important value you will want to determine is the total estimated calories you need to maintain your current weight. You start with the value you derived for BMR or RMR. Then you factor in the average level of physical activity with which you engage each day.
Multiply BMR or RMR by the factor that best describes your AVERAGE level of physical activity.
1.2 = Sedentary (Little or no exercise and a desk job)
1.375 = Light Activity (Light exercise or sports 1-3 days each week)
1.55 = Moderately Active (Moderate exercise or sports 3-5 days a week
1.725 = Very Active (hard exercise or sports 6-7 days a week)
1.9 = Extremely Active (Hard daily exercise or sports or a physically demanding job)
Now you have an estimate for your minimum safe caloric intake and an estimate for your total caloric needs to maintain your current weight. With these two values you can now determine your weight loss range.
Calorie needs to maintain current weight – minimum calorie needs = your weight loss range
Example:
Person A: 1800 calories (for maintaining current weight) – 1300 calories (minimum safe caloric intake) = 500 calories.
For person A reducing calorie intake by 500 calories or LESS each day would result in weight loss.
Person B: 2000 calories (for maintaining current weight) – 1200 calories (minimum safe caloric intake) = 800 calories.
For person B reducing calorie intake by 800 calories or LESS will result in weight loss.
I hope this article answers your question about how many calories per day you need to lose weight or maintain your current weight.
Can you speed up your metabolism to burn more calories? And how can physical activity positively impact your metabolism for faster weight loss? That’s what we’ll talk about in the next part of this series on Metabolism.
Till next time, watch those calories and eat healthy food!
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