fun with numbers
Jul. 29th, 2010 06:51 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
walkitoutFrom _The Hundred Year Diet_:
"Exercising was said to be useless, since it was purported to be scientific fact that a person would have to walk at least 30 miles to lose a pound. The converse, that walking 1 mile a day for 30 days would keep a pound away, was for the moment conveniently ignored. Time magazine quoted a physician at an AMA meeting in Chicago as stating that to lose a pound, you would have to climb the Washington Monument 48 times or do 2400 pushups. What was the point?"
There are a variety of things that could be done with these sentences. I'm not going to get into whether or not there really was a physician who said that at the AMA meeting.
Strictly speaking, I don't think that converse means what the author used it to mean. More or less like I don't think the NPR author meant "exponentially" in its strict sense a few days ago. Whatever.
The author says "purported to be a scientific fact" that 30 miles = a pound worth of calories. Purported is technically correct in the sense that that's what people were saying but 30 (flat and a relatively good surface) miles really _would_ take off about a pound. Then she _does not_ say "purported" or "alleged" or "was believed to be" when she quotes the AMA meeting attendee saying 48 times up the obelisk = a pound. Which _it does not_. As near as I can tell, 48 times _up_ the obelisk would = a pound and a half or thereabouts. 48 times _down_ the obelisk would equal about half that -- call it three quarters. 48 times up and down (since you can't really repeat one direction any other way) would equal over two pounds but probably less than three, assuming you kept level hydration throughout the process. Which would be tricky.
I sort of wonder about an author writing about diets that uses purported and converse and doesn't point out the suspiciousness of that obelisk calculation. Just because you're writing history doesn't give you any excuse for sloppy writing or innumeracy.
"Exercising was said to be useless, since it was purported to be scientific fact that a person would have to walk at least 30 miles to lose a pound. The converse, that walking 1 mile a day for 30 days would keep a pound away, was for the moment conveniently ignored. Time magazine quoted a physician at an AMA meeting in Chicago as stating that to lose a pound, you would have to climb the Washington Monument 48 times or do 2400 pushups. What was the point?"
There are a variety of things that could be done with these sentences. I'm not going to get into whether or not there really was a physician who said that at the AMA meeting.
Strictly speaking, I don't think that converse means what the author used it to mean. More or less like I don't think the NPR author meant "exponentially" in its strict sense a few days ago. Whatever.
The author says "purported to be a scientific fact" that 30 miles = a pound worth of calories. Purported is technically correct in the sense that that's what people were saying but 30 (flat and a relatively good surface) miles really _would_ take off about a pound. Then she _does not_ say "purported" or "alleged" or "was believed to be" when she quotes the AMA meeting attendee saying 48 times up the obelisk = a pound. Which _it does not_. As near as I can tell, 48 times _up_ the obelisk would = a pound and a half or thereabouts. 48 times _down_ the obelisk would equal about half that -- call it three quarters. 48 times up and down (since you can't really repeat one direction any other way) would equal over two pounds but probably less than three, assuming you kept level hydration throughout the process. Which would be tricky.
I sort of wonder about an author writing about diets that uses purported and converse and doesn't point out the suspiciousness of that obelisk calculation. Just because you're writing history doesn't give you any excuse for sloppy writing or innumeracy.
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no subject
Date: 2010-07-30 03:48 pm (UTC)I suspect the obelisk thing estimated by distance alone, not taking into account the difference in calories needed to climb stairs rather than walk on the flat? No, wait: 30 miles is 158,400 feet, divided by 555 feet is 285 WM heights, or about 142 times up and down. Maybe they assumed that stair-climbing averaged three times more calorie-burning than walking on the flat? I haven't found a figure for calories per mile rather than calories per minute for either walking on the flat or stairclimbing.
I'm also wondering about that 30 miles = one pound; how did you figure it? I looked at it this way: if you walk about 4 miles an hour, 30 miles is about 7.5 hours, and walking is supposed to burn about 300 calories an hour (292 per http://www.dummies.com/how-to/content/following-a-cardio-plan-for-weight-loss.html), so that's only about 2,400 calories, not 3,500 (I can't imagine that this sort of simplified overview is using anything other than the generic 3,500-calories-equals-a-pound-of-fat thing).
calories
Date: 2010-07-30 07:03 pm (UTC)The rule of thumb I have learned is that it takes about 100 calories for a person of average size to travel a flat and level mile. It sort of does not matter (but more about that below) whether they run it, walk it, amble it, etc. (crawling or for that matter swimming is more calorically intensive). A much smaller person (40 pounds) or a much larger person (300 pounds) will deviate enough from the 100 calories to matter, but that's not where the AMA attendee was going with this. I don't know where the dummies guide got their estimates, but they look off by a fair amount. 30 miles at 100 calories to a mile falls within my "burns a pound" range, so I was prepared to accept it, especially since they didn't specify flat and level, and most places have at least moderate up and down that would cover the remaining calories.
I'm not sure how the obelisk thing was calculated, but I figured it by finding someone who had a per step up (.11 kcal) and per step down (.05 kcal) measurement and multiplying it by the number of steps in the Monument (89x). Weirdly, almost exactly 100 calories going up and half that going down -- _way_ off from the 4800 calculation.
Here's what I found -- I didn't follow the citation:
http://answers.google.com/answers/threadview/id/728828.html
I would have accepted the storytelling/Gladwell explanation, except for the mismatch (purportedly on the number I thought was within range, but no question applied to the number I thought was incredibly far off).
What I learned (does not matter how you cover the ground) may not be true. And the dummies numbers may not be low. See here:
http://www.runnersworld.com/article/0,7120,s6-242-304-311-8402-0,00.html
Re: calories
Date: 2010-07-30 07:45 pm (UTC)I think that 3500 calories for a pound of fat may already be a corrected value taking water weight into account. One pound, or 454 grams, of fat times 9 calories per gram is 4086 calories. See http://forum.bodybuilding.com/showthread.php?t=788793, which quotes an article no longer available except on the Wayback Machine: http://web.archive.org/web/20080121120916/http://www.hhp.ufl.edu/faculty/pbird/keepingfit/ARTICLE/fatcalories.HTM.
"When we burn fat, or other nutrients, heat is produced, which is measured in calories. As you note, each gram of fat generates 9 calories, and 454 grams equals one pound. But a pound of fat is not all fat. It's about 10% water. All of our body tissues--fat, muscle, bone, skin--contain some water. And water has zero calories.
"In addition, not all the nutrients we eat are completely absorbed from the digestive tract to meet metabolic needs. In the case of fat, roughly 5% is eliminated in the feces. This 10% water content and 5% non-absorbed fat accounts for the 15% difference between your calculated 4086 calories and the actual 3500 calories in a pound of fat."