How to keep track of the calories you’re burning

One of the questions we hear most often is this one: How do I figure out how many calories I burn?

This is an area loaded with hooey and misinformation. Let’s take it from the top.

In a typical day, you burn calories four ways:

* basal metabolic rate (BMR), or calories used when sedentary;

* thermal effect of feeding (TEF), or calories burned digesting food;

* physical activity (anything you do besides sitting: walking, piano playing, shadow boxing); and

* excess post-exercise oxygen consumption (EPOC), that oft-hyped after burn from a workout.

To see how these might add up, let’s consider a hypothetical example we’ll call Miss Jones. She is 45 years old, stands 5 feet, 5 inches and weighs 135 pounds; she consumes 2,100 calories’ worth of food and drink a day.

(Caveat: The figures below areapproximate, vary widely between individuals and are subject to debate in the field.)

First: You can do little to change your basal metabolic rate, despite what some dietary supplement makers say. Worse, BMR declines with age.

Using a generic calculation for BMR, we derive a burn of slightly more than 57 calories per hour while sedentary.

Assume Jones sleeps for eight hours and is basically inert (sitting at some kind of screen, talking on the phone, driving, doing a crossword) for 11 more hours. She’d burn 1,090 calories in those 19 hours. Add eight more calories to account for her buffness, and we can round up to 1,100 calories.

Thermal effect of feeding is estimated at 10% of daily caloric intake.

Because the body works a little harder digesting protein than other nutrients and Jones’ diet is protein-rich, she “might burn another 20 or 25 calories” beyond the 210 a standard 2,100-calorie diet would consume, said Darlene Sedlock, associate professor of exercise physiology at Purdue University. OK, 235 calories for TEF.

Now, the fun: Jones found time for a 30-minute, 3-mile run, which burned 306 calories. Jones’ EPOC “is probably less than 30 calories” after her run, Sedlock said. So: 335 calories for the run and its resulting EPOC.

Luckily, Jones spent the other 4 1/2 hours of her day doing a variety of mild physical activities -- carrying groceries, cleaning her apartment, etc. These incinerated 700 more calories (for data: www.caloriesperhour.com).

For the day, she burned 2,370 calories and consumed 2,100 -- that’s a modest deficit that could, if sustained, support weight loss.