How to Calculate How Many Calories You Need to Eat to Lose Weight

 The key to fat loss is first figuring out how many calories you should be burning or skipping each day. There are many calorie calculators available on the internet that allow you to calculate how many calories you should eat in a day in order to lose a certain amount of weight by a certain date.  These calculators are very helpful, however, many people wonder what formula these calculators are using to display accurate information. Hopefully this post will answer that question as well as help you calculate how many calories you burn just by existing, and how many you need to cut to lose weight.

Mifflin – St Jeor Equation

For those of you that studied nutrition in college, you might remember learning the “Mifflin – St. Jeor Equation”.  This equation is used in clinical settings to determine a patients caloric needs based on their basal metabolic rate (BMR) and activity level (as you can imagine, most hosptial and long term care patient’s aren’t very active).  The formula is fairly complicated, however, anyone can figure out their own BMR if they have a calculator on hand. 

Why This Formula?
The ADA (American Dietetic Association) published a comparison of various equations. The Mifflin-St Jeor was found to be the most accurate.

10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) + 5

10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) – 161.

See! I did say it’s a little complicated (maybe I should have said “VERY” complicated).

The Calorie Needs Calculator currently uses the formula proposed by MD Mifflin and ST St Jeor. Click on the link and try it out for yourself.

After calculating your BMR, you can then factor in your activity. Depending on the exercise level chosen, the BMR will be multiplied by anything from 1.2 to 1.9.

Account for your activity level. Since you (hopefully) do not sit still in bed all day like a hospital patient, you should account for the calories you burn through activity. To determine your total daily calorie needs, multiply your BMR by the appropriate activity factor:

  • If you are sedentary (little or no exercise) : BMR x 1.2
  • If you are lightly active (light exercise/sports 1-3 days/week) : BMR x 1.375
  • If you are moderately active (moderate exercise/sports 3-5 days/week) : BMR x 1.55
  • If you are very active (hard exercise/sports 6-7 days a week) : BMR x 1.725
  • If you are extra active (very hard exercise/sports and physical job or 2x training) : BMR x 1.9
  • For example, a 19-year-old woman who is 5’5” and 130 pounds would plug her information into the calculator and find out that her BMR is 1366.8 calories. Then, since she is moderately active, exercising 3-5 days per week, she would multiply 1366.8 by 1.55, to equal 2118.5 calories. That is the number of calories that her body burns on an average day.

This provides us with maintenance calories. To get the fat loss figure – 20% is subtracted. The extreme fat loss figure has 40% subtracted BUT – there is a “rock bottom” figure that equates to 8 calories per pound of body weight – the extreme fat loss will never be less than this amount

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