How to Calculate How Many Calories You Need to Eat to Lose Weight |
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 taking in each day. Many people skip right over this step and jump straight into “eating healthy” but if you have no idea how many calories you should be eating, how can you ensure you are feeding your body what it needs to function and in turn will allow you to lose the fat you want to shed? Missing this part of the process is what most often causes the dreaded plateau, aka the "fat loss brick wall". So do yourself one huge favor and take a few minutes to do some quick calculations.
Steps
1. Find out what your Basal Metabolic Rate (BMR) is, or specifically, how many calories your body needs to function properly if you spent the entire day sedentary. Resting metabolic rate (RMR) is often used interchangeably with BMR; although they are slightly different, estimating either is sufficient for the purpose of losing weight. To calculate your RMR, you can use the Mifflin-St Jeor equation.[1]:
RMR = 9.99w + 6.25s - 4.92a + 166g - 161
w = weight in kilograms; if you know your weight in pounds, divide by 2.2 to get your weight in kilograms
s = your height in centimeters; if you know your height in inches, multiply by 2.54 to get your height in centimeters
a = age in years
g = sex = 1 for males, 0 for females
2. Account for your activity level. Since you (hopefully) do not sit still in bed all day, you must add in the calories you burn through activity. Once you have your BMR, use the Harris Benedict Formula below to determine your total daily calorie needs depending on your activity level.
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
So, to give you an example, a 30 year old woman who is 5’-6” and 150 pound would plug her information into the calculator and find out that her BMR is 1476.6. Then, since she is fairly active, exercising 3-5 days per week, she would look at the formula above and see that she would multiply 1476.6 by 1.55, to equal 2288 calories. That is the number of calories that her body burns on an average day.
3. Adjust for fat loss. This is where most people screw up severely. They take the deficit too far. In order to lose one pound, you must be in a deficit of 3,500 calories per week, or 500 calories per day (3,500 calories divided by 7 days). This is where the topic of "starvation mode" comes into play. If you have a lot of weight to lose, you are safe with a deficit of 1000 calories per day, or a 2 pound loss per week. If you are on your last 10 pounds or less, you will want to stick closer to the 1 pound per week range, or a deficit of 500 calories per day, so as not to go too low with your daily calories.
When you first begin, you may lose more than this for the first few weeks, which is normal, that is water weight and bloat. After the first few weeks, you should even out at a 1-2 pound loss per week. Be aware, you do not want to lose much more than this, as it will not be fat--anything above this range will be muscle for sure.
If the woman’s goal weight is 130, she would have a total weight loss of 20 pounds. She would want her weight loss goal per week to be between 1-1.5 pounds per week, so that she does not take her calories too low. Her total daily intake of calories should be between 1563 and 1788. As she begins to lose weight, she will want to recalculate her BMR, and then stick to the 1 pound per week (500 calorie deficit per day) range as she gets within 10 pounds from her goal weight. Always watch what you eat and how much you eat
Tips
You are probably thinking, wait a minute, I don’t want to prolong this, I am going to just go for the gold and lower my calories a ton to get to my goal quicker. That is the fastest way to hit a metabolic brick wall! You go too low with your calories and your body shuts down. So, if you only have a few pounds to lose be patient and do it slowly.
Bear in mind that approximately 70% of weight loss can be accomplished by modifying one's diet and caloric intake.
Stay hydrated as water is needed for fat-burning to take place.
Warnings
With any fat loss program, you will want to incorporate a weight training program as well, so that you keep your muscle and don’t turn into a pile of mush and skin.
If you sit at a desk all day, but work out 6 days a week, then you would probably fall under moderate activity rather than very active. It is common for people to over or underestimate their activity level, so pay attention. Since these are just estimates, keep an eye on your fat loss and if you start losing too fast or too slowly, then you will want to adjust your calories up or down accordingly.
Before starting any weight loss plan, it is recommended one consult a physician.
Once you have lost your weight, don't forget to calculate a new RMR (because your calorie usage will sink).
Sources and Citations
http://livewell360.com/2008/06/how-many-calories-should-you-eat-for-fat-loss/ Original source. Shared with permission.
Online (free) Metabolic Rate calculator for those who aren't sure of their math: http://www.bmi-calculator.net/bmr-calculator/
1. David Frankenfield, Lori Roth-Yousey, and Charlene Compher. May 2005. Comparison of Predictive Equations for Resting Metabolic Rate in Healthy Nonobese and Obese Adults: A Systematic Review. American Journal of Clinical Nutrition 105(5):775-789
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