TypewriterFrom The Urbach Letter March 2009

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Math of Fat - The Engineer's Diet

When studying for my mechanical engineering degree 30 years ago, I had to take four advanced thermodynamics courses. Pretty intense stuff. But one of the remarkable things about learning the physical laws of the universe (which is what you do in "thermo," study matter/energy conversion), is realizing those laws hold true everywhere. Even in places you might not initially think of… like the human body. Engineers look at everything as a system. We draw boundaries on our "system diagrams" and look at what crosses that line. Fuel in, energy out. So… here's the equation:

3,500 calories = 1 pound body fat

Vitruvian ManHere's how it works: If you're now eating an amount of food each day that keeps you at a static weight, you're at equilibrium. If you make no other changes, and consume an additional thirty-five hundred calories of food or drink, you're going to gain a pound of real weight (i.e. fat, not water). Fortunately, it also works the other way around. If you consume 500 calories less a day, with no other changes, you'll lose a pound of real weight a week. Seems too simple, right? What about all that hubbub with low-fat diets, high fat/high protein diets, grapefruit diets, etc? While it's true the type of food does matter to some extent, it really has more to do with how hungry you are – and how these foods affect your hunger pangs. Remember matter/energy conversion. All the other aspects, kind of food, time you eat it, metabolism level, and so on, are secondary factors. There is only one way to lose weight and keep it off: eat fewer calories and exercise more.

This was all validated in a study by Dr. Frank Sacks at the Harvard School of Public Health published in the February 26, 2009 issue of the New England Journal of Medicine, which spawned hundreds of news reports last week. The study confirmed that it all comes down to how many calories you're putting in your mouth (and how much you're moving the rest of your body).

A rough guideline for number of "allowable" calories a day for an average person (somebody who works in an office, and doesn't visit the gym that much) is about 12 calories per pound of body weight. A 120 pound woman would therefore have an equilibrium level of about 1440 calories a day. A 180 pound man's level is 2160 calories a day. Most people eat more than this, and don't exercise. That's why most people are heavy and getting heavier. It sneaks up on you. An extra bag of potato chips a day (150 calories per ounce) = 15 pounds a year. The only way out is to reduce your calories below your equilibrium until you're at your target weight, then eat reasonably after that. It's called "lifestyle," not a diet. That new lifestyle starts by knowing what you're eating. Read labels. Consult a calorie counter book or web resource. If you can't imagine how you're going to cut out 500 calories a day, don't. Cut out 250 and get on the treadmill for half an hour. I lost 25 pounds this way (I'm back to nearly my college weight now), and have kept it off (mostly) since I wrote the first version of this article seven years ago.


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