I usually use the metric system, but in this book I've stuck to English units throughout. Even scientists who work all day in metric units think of themselves as ``five eleven, one-sixty.'' Metric units would only confuse U.S. readers and make the essential techniques in the book less accessible. I apologise to readers in more enlightened areas of the world. I've also conformed to the somewhat sloppy practice in most nutrition books of using ``calorie'' to mean what is more precisely termed ``kilogram calorie'' or ``kcal''--the energy required to raise the temperature of one kilogram of water one degree Celsius. The ``gram calorie,'' 1000 times smaller, is cumbersome when discussing the energy content of food. In Europe, food energy value is frequently given in kilojoules (kJ), the metric unit of energy. To convert kilojoules to kilogram calories (``food calories''), divide by 4.184.
The Excel spreadsheets allow you to specify whether weight is measured in pounds, kilograms, or stones; each spreadsheet which uses weight measurements contains a cell near the top which specifies the unit of weight. If set to 1 (as supplied), weights are in pounds. If you change the cell to 0, weights are in kilograms. If you set it to -1, weights are measured in stones. Also included is UNITS.XLS, an Excel worksheet providing conversion factors among all the odd English units encountered in connection with food (teaspoons per cup, for example), plus their metric system equivalents.