Serving Size and Calorie Counting

When you want to lose body fat, the only way to do it is to burn more calories than you consume.  If you burn approximately 3500 calories more than you eat, your body will metabolize about 1 pound of fat to make up the difference.  Now this has some interesting implications...  Can you lose weight eating only Krispy Kreme donuts?  Well, yes.  You just need to eat less calories worth than you consume.  Of course, an all-Krispy-Kreme diet would almost certainly lead to other nutritional complications.  You would also probably be hungry most of the time because eating few enough donuts to lose weight would probably not be very satisfying.  But it could be done.

If you are keeping track of you calorie intake, it is important to know what your actual calorie count is.  Small errors add up over time.  An extra 10 calories a day, which is less than one teaspoon of sugar, adds up to 3650 calories over a year; that's more than a pound of fat!  Fortunately, there are standard nutrition facts labels on virtually all packaged foods sold in the United States, like this one on tortilla chips:

So, according to this label, the serving size is 28 grams, which is 140 calories.  The FDA has rounding rules that allow manufacturers to round to the nearest 10 calorie increment for values >50 calories, so that means the real value is somewhere between 135.0 and 144.9 calories per 28 gram serving.  Also, most people don't have or regularly use a food scale, so the label often helpfully provides a translation of the serving size into pieces.  Here that is "About 13 chips."  So when I was making nachos the other day I wondered "how close is 'about?'"  The answer was, not too close:

Counting out 13 of the most uniform chips I could find onto a scale (yes, I zeroed out the paper plate), I measured 34.7g, which is 6.7g, or 24% more than the 28g serving size.  That means that if I count out 13 chips and think I'm eating 140 calories, I would really be getting closer to 174 calories.  To get the 28g serving size, I should really eat about 10.5 chips.

To be really precise, I should note that the primary measure for the serving size is given as 1 ounce, which is really closer to 28.35 grams.  But that .35 grams is an error of only 1.25%, which is dwarfed by the 24% error above.  There is also some normal chip-to-chip variation, which I didn't measure.  And often a "chip" is actually broken and missing part.  But ultimately, if you want to confirm serving size, the best way to do it is by weighing your food.

Do you ever keep track of your calorie intake?  Leave a comment below!

Writers Do Math, When Necessary

Writers read, a lot, according to several authors whose opinion and craft I respect. Most notably, I remember Dean Koontz in his book on writing talking about the need to read constantly. I also just like to read, because it is entertaining, and fun, expands my vocabulary and world view, gives me things to talk about with friends, and quite honestly, it's easy to do. But it also takes time. And while "I don't have time" is the frequent excuse of people who waste vast amounts of time doing inconsequential things (I'm looking at you, television, FaceBook, Hulu, YouTube, and most of the Internet), it is still hard to muster the 8 - 30 hours that it can take to read a good book.

In order to consume more books, I started listening to books on tape years ago, and I now try to have a constant stream of books on CD from the local library in my car. They're free, they're extremely convenient, and given the limited selection the library can carry, they tend to be only the most popular titles, which are often things I wanted to read anyway. Even with my relatively short commute, I get through at LEAST 30 minutes of "reading" a day, and if you include all other driving, I probably clear about a CD a day on average. That means I can listen to a 15 CD novel in about 2 weeks. Yes, you can argue about the merits of listening to someone read the text versus reading the printed page yourself, but I find the narration usually doesn't get in the way, and the time savings is well worth it.

The latest book I'm listening to is Deception Point by Dan Brown. It's a techno-political thriller that he wrote in 2001, after Angels and Demons, and before The Da Vinci Code. I'm on disk 10 of 15 so far, and the story is okay, although it frequently feels a bit thin in places, like he's milking more pages than are really merited from many of the story elements. But the things that have bugged me the most are engineering related nits which could have been largely avoided with some basic math and physics.

The most glaring has to do with the weight of a rock. I'll attempt not to spoil any of the story here, but several times there are references made to a rock which is initially described as "10 feet in diameter" weighing "eight tons." The rock is described as approximately spherical, which would give it a radius = diameter / 2 = 5 feet. The volume of a sphere is 4/3 * pi * radius^3, which means the rock has an approximate volume of 1.333 * 3.14159 * 5 * 5 *5 = 523.5 cubic feet. Using Google, we can easily convert this to liters and we get 14824 liters. Now, if it were made of WATER, and not rock, that 14,824 liters would weight about 14,824 kilograms = 32681 pounds = about 16 tons. But it's not water, it's ROCK. The rock is described as granite like, which would have a specific gravity, or density relative to water, of about 2.6. This means that it would weight 16 * 2.6 = about 41.6 tons. But even if we say it is the least dense rock we can come up with, pumice stone, the air-filled "floating rock" ejected by volcanoes, it would STILL have a specific gravity of 0.64, and a mass of about 16 * 0.64 = 10 Tons. The "eight tons" sounded wrong when I first read it, and now, especially after doing the math, it grates on me every time it is repeated.

So the follow-up question, of course, is why did this happen? Is there some major plot point I haven't yet gotten to about the rock being only 25% of the weight it should be? Or was it just sloppiness by Dan Brown, and then by his editors? Given how lauded Brown is for his extensive research, it seems strange and jarring that such a relatively obvious factual error made it into the book... And if anyone reading this knows Mr. Brown, I'd love to hear his explanation!