Tuesday, May 13, 2008

Metabolism and You: Some Numbers

BMR: something interesting I’ve learned about metabolism while trundling along my weight loss journey. There are various methods of calculating what your metabolism is probably doing if you can’t afford or don’t want to go through lengthy or costly metabolic testing.

Here’s the idea – you want to know approximately how many calories you burn on any given day by taking your BMR (Basal Metabolic Rate) and adding in your typical activity level. Once you have a pretty good idea of that, you can figure out how much of a caloric deficit you want to create by eating somewhat fewer calories than your total burn. A calorie deficit means that you are setting the stage for weight loss. If you don’t want to lose weight, but instead maintain your current weight, you’ll want to eat around the same calories as you burn.

The BMR calculation produces a number that tells you how many calories you would burn if you did nothing but stay in bed and breathe all day – no activity at all, just how many calories you would need to continue existing. There are a number of calculations and online calculators, and I’m sure each has its proponents, but suspect that for most of us they’re going to come up with numbers fairly similar.

You don’t want to eat fewer calories than your BMR because if you deprive yourself below BMR, your metabolism will slow down so that you burn less – a double edged sword for sure. This is where regular exercise – both strength training and cardio – can help, by increasing your BMR. Exercise also just makes you generally more healthy and fit and boosts your ability to burn energy.

Here’s a link for more info about BMR: Wikipedia Link. This BMR calculation uses metric measurements, so if you need them, here are some converters for pounds/kilograms and inches/centimeters: Pounds/Kilograms and Inches/Centimeters

This is the BMR calculation for women that I’ve used to calculate my own BMR, as an example. Figure out and plug in your own numbers to see what you’re burning.

655 + (9.6 x weight in kilograms) + (1.8 x height in centimeters) - (4.7 x age)

655 + (9.6 x 65.77089365) + (1.8 x 166.116) - (4.7 x 51)655 + 631.4005 + 299.0088 - 239.7 = 1345.7093 BMR

This weight in kilograms is 145 Centimeters is converted from 5' 5", age now 51

For men the calculation is somewhat different:
BMR = 66 + (13.7 x weight in kilograms) + (5 x height in centimeters) - (6.8 X age)

If I were male, my calculation would look like:
66+ (13.7 x 65.77089365) + (5 x 166.116) – (6.8 *51)66 + 901.061 + 830.58 – 346.8 = 1450.78 BMR

Using the multipliers for activity level:
1.2 multiplier for sedentary
1.375 multiplier for lightly active (light workout day)
1.55 multiplier for moderately active (probably a typical day for me)
1.725 multiplier for very active (if I really push it)

These are my estimates for burn at different activity levels:
Sedentary burn: 1615
Lightly active: 1850
Moderately active: 2086
Very active: 2321

And if you want to do it the easy way, here’s a link to an online BMR calculator.

No comments: