Like any other deer hunter, John Porcari must drag his killed quarry out of the forest. But unlike most others, he knows just how many calories that effort takes him: 13 per minute. (That means he needs to drag a deer 12 minutes to burn off each 3-ounce venison steak he eats.) Porcari also knows the number of calories burned by a vigorous game of paintball (7 per minute), yoga (4 per minute), and sex (5 per minute).
Porcari is not so much an exercise nut as an exercise physiologist, at the University of Wisconsin, La Crosse. For the last 20 years he has been measuring the caloric expenditure of various tasks. As recently as 15 years ago, that meant that subjects had to breathe into a meteorologic balloon while they roller-bladed, at which point Porcari used the balloon's oxygen concentration to derive calories burned.
Today, he straps a several-pound, portable metabolic analyzer that's "about the size of a package of English muffins" onto each of his subjects as they snowshoe or kickbox. Each device costs nearly $40,000, but the benefit is that "people can pretty much do the activity without being encumbered by it," says Porcari.
To measure deer-dragging, an activity he calls "strenuous as heck," Porcari had his subjects lug road kill that he obtained from the Department of Natural Resources and standardized to 125 pounds by either chopping off a few limbs or placing weights into its chest cavity. "A fair number of people have dropped dead deer-hunting," he says. Next on his study list: Elk hunting. Porcari likes to vary his own methods for burning calories, sometimes using walking poles when he's out for a stroll for an increased energy expenditure of 22% (Res Q Exercise Sport, 68:161-6, 1997).
There are about 100 people studying such expenditures. James Levine, an endocrinologist and professor of medicine at the Mayo Clinic, uses what he calls "magic underwear," which can measure the wearer's movements and body postures 120 times each minute, to focus on less strenuous activities. Last year, he reported in Science on what he calls nonexercise activity thermogenesis (NEAT) - the calories burned by daily activities such as sitting, walking, and even fidgeting (Science, 307:584-6, 2005). According to Levine and colleagues, NEAT plays a key role in distinguishing lean people from the obese, accounting for an extra 350 calories burned daily by the lean, on average.
These new devices are making calorie counts much more precise than they have ever been, says Patricia Nixon, associate professor of health and exercise science at Wake Forest University. Actual calorie counts per activity fall within a range, but while "one person plays tennis very aggressively, someone else walks to pick up the ball." The averages provide points of comparison, she says. Calorie counts are compiled in "A Compendium of Physical Activity," last updated in 2000 (Med Sci Sports Exercise, 32(suppl):S498-S516, 2000) and are available for Web-browsing procrastinators at sites such as www.caloriesperhour.com.
Levine is convinced that his findings hold the antidote to obesity, and he's taken it upon himself to redesign office environments in kind, starting with his own. For the past year, Levine has been running his lab while walking - at a treadmill desk station from which he can create Power Point presentations and make phone calls. At the optimal speed of one mile per hour, "you don't sweat, you can wear regular clothes, and you don't need a change of shoes," he says. Levine burns 800 calories a day more than if he were sitting at a desk. He has gotten more than 300 people at Mayo alone, including the CEO, to participate in his Office of the Future. "All we've done is ask a very, very simple question", Levine says: "[What happens] if you go into an office and removed all the chairs? It's a completely cool-looking work environment."