Question: How does one calculate the amount of calories needed for daily food intake?
Answer: Although a 2,000-calorie diet is often cited on nutrition labels, that's just a rough guide.
Your base metabolic rate is about 1 calorie per kilogram per hour. Multiply your weight in kilograms by the 24 hours in a day. This is the number of calories you burn just by being alive each day.
Now factor in activity. Depending on your activity level, multiply your base metabolic rate by the following factors:
For light activity: 1.3.
For moderate activity: 1.4.
For heavy activity: 1.5.
The resulting number is your necessary food intake. (Most Americans are in the "light activity" level.)
If this seems like too much work, you can also measure your oxygen consumption (the universal fuel of metabolism) while at rest, making it easier to figure out how to lose weight. You can do this by breathing into a device (similar to a scuba-diving mouthpiece) that uses sensors to measure volume of air, oxygen content, temperature, barometric pressure and relative humidity. The device is called a BodyGem and is now being used in some gyms.
But of course, metabolisms vary by individual. All any number does is provide a guideline.
Stephanie Oakes is the fitness correspondent for Discovery Health Channel and a health/fitness consultant. To submit a question, e-mail email@example.com. She cannot respond to every query.