You will recall that in last week’s column I was musing about the difference in weight of our two cats, George the chubby marmalade one and Evie the black and svelte one, despite the fact that there is not much difference in their food consumption. I also discussed some of the perils of being overweight and in particular, obese. So what is the difference in the two cats? The answer is metabolism. Some of us burn more energy at rest than others. All of us know someone that remains rail thin despite consuming more in an average day than we do. Metabolism again, so let’s look at this whole question of rate of metabolism(energy burn) and weight.
Evie…Keep guard while I grab us a snack!!!!
To start, I would like to say that there is nothing complicated about
weight gain and/or loss, no mystical formula, drug or supplement that
will really do very much over the long haul and although the answer
to maintaining the correct weight is easy, putting it into practice for
many of us is not and the whole key to this is the rate at which we
burn calories; our metabolic rate.
So what is metabolic rate? Well simply (or not so simply) put it is the number of calories that we burn at rest per hour per square metre of
body surface area and is approximately 40 calories per hour per sq.
metre plus or minus 25% (Getting a bit complicated?). The average
man has a body surface area of about 1.9 sq. metres so will burn approx. 76 calories per hour doing nothing. The average woman, 1.6 sq.metres of body surface area. Ah, but we have to remember the + or – 25%, so the range becomes 57 to 95 calories per sq. metre of body surface area per hour which is quite a difference if you are the lower range burner vs. the upper range. So now you know why some can consume a lot more than others and not gain.
The mitochondria (the little engines in our cells) are either revving higher or there are more of them in the high end burners than in the low end. In days of yore when food was scarce there was an evolutionary advantage to being at the lower end (better survival on the same amount of food) today when there is food aplenty, there is not, and we slow metabolisers have to watch our intake really carefully while those speedy types do not.
So back to the cats, the average cat has a body surface area of approx. 0.36 sq. metres and burns about 56 cals per sq. metre of body surface area an hour plus or minus 25% (about 20 calories per hour on average with a range of 15 to 25 cals. per hour), so poor old George is
probably burning his 15 cals. per hour while Evie is zipping along at 25. Theoretically (and practically) this means that she can eat 2/3 as much again as he can and not put on any more weight. (That’s a lot) So there you have it, one fat cat, one thin cat, the difference in our genetic make up that determines how efficiently (or not) we burn energy. Next week we can get into the meat (no pun intended!) of the matter, with some practical solutions to weight maintenance or loss despite all of this.
Dr. Philip A. White
On Call 24/7 with Dr. White Thursday, June 18, 2009
http://www.SomaLife.com
