Friday, January 05, 2007

There Are No Absolute Truths

The idea that absolute calorie intake minus calories expended is meaningful is simply wrong. I have two examples where this failed.

I met a woman years ago who was grossly overweight. About five feet tall, and over four hundred pounds. She looked for a diet where she could maintain her weight. She gained weight on a 700 calorie diet. She was quite active, and, no, evidence suggests that she did not cheat. Finally, she was able to maintain her weight on a 500 calorie diet. Once stable for a year, she underwent surgery to remove some 190 pounds. Still a bit chubby. Most people would not survive long term on 500 calories.

When i was in school, i ran cross country. My workouts were 15 miles, twice a day. That's 30 miles a day. 210 miles a week. 14 weeks. My calorie intake was not measured precisely, but did not increase. It was probably around 2500 calories. According to Dr. Cooper, my calorie expenditure was over 4000 calories per day. I should have lost weight, right? The actual result was a 10 pound weight gain.

One reason my intake did not increase was that i could not afford to eat more. The caffeteria provided "all you can eat", but my runs ran into both breakfast and dinner. The result was that they closed just a minute or two after i arrived, every day. So, no seconds.

Absolute calorie figures do not seem to understand how physiology really works. One summer, i decided to bicycle to work. (My new job had showers). When i started, my average speed was under ten miles per hour. At the end of the summer my average speed was 21 miles per hour. At these speeds, drag increases with the cube of the speed. So, a doubling in speed requires an eight fold increase in power. To achieve this, one's cardiovascular system needs to adapt. It does this by increasing efficiency and by increasing capacity. But base efficiency of physiology across a population behaves with a bell curve distribution. There are going to be outliers, like the woman i met above.

What does work is relative lifestyle changes. Eat a little less. Exercise a little more.

These aren't many data points, but in the grand tradition of physics, i'm more than willing to fit a ninth order polynomial to them.

Remember, there's an exception to every rule. Even this one.

1 comment:

Tag said...

Hi Steven,
lifestyle changes are difficult. the inertia of comfort is hard to overcome. having quit smoking, my lifestyle changes haven't yet included a proper diet and exercise routine. instead eating replaced smoking...and the pounds incrementally gain and the inches incrementally grow.