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How many calories do I need to lose weight?

For those of us on the fitness path with a short-term goal of weight loss, knowing how much you should eat can be tricky.  Eat too much, you will maintain or gain.  Eat too little and you will also maintain or gain.  What’s a girl (or guy) to do?  There are plenty of apps out there like myfitnesspal that can take out some of the guesswork for you.  You answer a few questions and they tell you how many calories to eat.

But, if you want to verify accuracy (especially if you have hit a plateau), here’s the formula:

First, you need to know your BMR (Basal Metabolic Rate) – this is how many calories your body burns without any notable activity.  It is calculated using your height, weight and age but does omit lean body mass.  If you are super muscular, you will need a little more calories than what this equation will yield.

  • Women: BMR = 655 + (4.35 x weight in pounds) + (4.7 x height in inches) – (4.7 x age in years)
  • Men: BMR = 66 + (6.23 x weight in pounds) + (12.7 x height in inches) – (6.8 x age in years)

Next we use the Harris-Benedict Principle (the formula most use) to determine our calorie needs based on Activity level.

  • Sedentary = BMR x 1.2
  • Light Activity (exercise 1-3 times/week) = BMR x 1.375
  • Moderate Activity (exercise 3-5 times/week) = BMR x 1.55
  • Very Active (exercise 6-7 times/week) = BMR x 1.725
  • Extra Active (exercise twice daily) = BMR x 1.9

So, to give you an idea of what this looks like for myself and my husband:

Me (131 pounds, 5’0″, 36 years) = 1337.65 BMR x Activity 1.725 = 2307.45
Hubby (180 pounds, 6’2″, 37 years) = 1953.3 BMR x Activity 1.375= 2685.79

  • 1 pound of fat = 3500 calories

To lose 1 pound per week, you need to be at a deficit of 500 calories per day.  For 2 pounds per week, you need to be at a deficit of 1000 calories per day.  You never want to go below 1200 calories or you’ll send your system into starvation-mode!

I’d really like to lose up to 20 pounds, so I am targeting a deficit up to 1000 calories and generally aim to eat 1300-1500 calories, regardless of how many calories I burn exercising (since Activity has already been taken into consideration).

Now that you know how many calories you can eat, keep track and reach your goals!

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