Mike Blamires has recently put some very good posts on his blog. Of particular interest to me is the one from 20 March entitled Counting The Calories.
Maybe it's just my maths background but I find stuff like this highly interesting and useful ... or maybe it's a Gnarls Barkley moment again (see Tuesday 17 March).
Anyway, using the formula and applying it retrospectively to my 24 hr run in London last October we have, using the Harris-Benedict Equation, my Basal Metabolic Rate is
1.752 * (66 + (6.23 * my wt in lbs) + (12.7 * my ht in inches) - (6.8 * my age in yrs)) equals 2436 kcal per day
The running itself used 1 * 57.5 * 228.011 equals 13111 kcal
Therefore in that 24 hr period I needed a total of 15547 kcal
The problem now is that when exercising, the human body can only process 240 to 280 kcal per hour MAXIMUM which is 5760 to 6720 kcal per day. Which is at least 8800 kcal less than I need.
As Mike says the deficit is made up from body fat reserves. About a month after that race my body fat was measured at 14.1% ie about 17.88 lbs. The kcal here is 17.88 * 3500 equals 62500 which is easily enough.
One slight amendment to make here though is that I don't really want to lose more than 3% of my bodyweight as this will impair my performance. 3% of my weight is 3.8 lbs which, as fat, will have 13300 kcal. Again, more than enough.
For energy expenditure during a race, the table on this page gives more accurate results. According to the table I used 12997 during the 24 hours.
Thanks for all this Mike - have a good run in the desert.
In the next few days (maybe even tomorrow !!!) I'll email the first draft for helping my Run To London. I know you'll be too busy to have an in depth look though.