Looking at the numbers

The math of biology intrigues me.

There’s really few hard answers in biology. Doctor’s don’t understand so much of how the body really works. Nutrition advice changes daily, new studies show connections one day and then are refuted the next. What we knew about biology ten years ago is out of date today. Even five years. Even one year.

The laws of thermodynamics, however, are well known and come down to numbers. And they apply to fat burning.

Livestrong, like many calorie counting systems, uses the Harris-Benedict Equation. Derived from analyses of metabolism, these gents derived an equation to estimate a subject’s basal metabolic rate (how many calories your body uses while completely at rest) and then multiply it based on your activity level.


To get my BMR, you use the below. (This is the calculation for men. The female one is slightly different).

BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) 
      - (5.677 x age in years)

I weigh 148.869 kg, am 182.88 cm tall, and I’m 41 years old. So:

88.362 + (13.397 x 148.869) + (4.799 x 182.880) - (5.677 x 42)
88.362 + (1994.398) + (877.641) - (238.434) = 2721.967 kilocalories/day at rest

You then multiply this by a ratio for your lifestyle level. I lead a generally sedentary life so my daily calories needed get multiplied by 1.2.

2721.967 x 1.2 = 3266.360 kcal

So this is the number of calories a day I burn just by my regular routine. No extra exercise. If I consume this much in food, I won’t change my weight.

Pound by pound

A pound of fat has 3500 kcal. Over a week, if you cut your calorie intake by 500 kcal a day, your body burns a pound of fat to fuel the deficit. If you can cut your intake by 1000 kcal a day, you can lose two pounds a week. Which most doctors and nutritionists I’ve spoken to agree is the most you should attempt to lose – lose any faster and it comes out of other sources in your body, like your muscles.

I now target myself to lose 2 pounds a week using these calculations. Everyday I track myself to try to hit around 2300 calories. But if I go over a bit, it’s not that bad. Yesterday I went over my calorie goal by about 100 kcal. But as long as I don’t go over 3300, I’m still losing weight.

For me this helps. I’ve fallen into the trap of, “Crap. I’ll miss my goal today. Might as well eat this tub of butter.” Knowing that I can go over and still be good takes the pressure off a bit.

More info on the Harris-Benedict equation is here.

Current weight: 328.2 pounds
Words typed today: 425

About shuffledog

40+ stepfather and husband. King of the geeks.

Posted on July 17, 2013, in Health, Weight and tagged , , . Bookmark the permalink. 1 Comment.

  1. To lose weight we need to shut off our computers once in a while (hugs)

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