Swiping your credit card at the pump burns only five fewer calories than walking into the gas station to pay. Opening a bag of pre-sliced veggies expends just 12 fewer calories than washing, slicing and chopping fresh ones. Riding the elevator uses 15 fewer calories than climbing three flights of stairs.
But add up the energy it takes to do these and 17 other common tasks in a sedentary manner--and compare the result with the calories burned performing the same tasks actively--and the difference is the energy equivalent of 2 1/2 pounds of body fat over a month and 30 pounds over a year, says a Dallas epidemiologist who is a pioneer in the growing movement to "jump-start" our increasingly obese, sedentary society.
"When you expend a little less energy doing numerous tasks over time, the end result can be a substantial weight change," says Steven N. Blair, director of research at the Cooper Institute, which was founded in 1970 to study the effects of exercise on health. Blair also served as senior scientific editor for the landmark U.S. Surgeon General's 1996 Report on Physical Activity and Health, which concluded that a modest amount of moderate exercise could reduce the risk of numerous chronic diseases including heart disease, type 2 diabetes, hypertension and some cancers.
Though much of the debate surrounding America's obesity epidemic focuses on our "super size" junk food diet, Blair says the major--and often unrecognized--culprit is the "gradual ratcheting down of daily life activity." In a recent editorial in the Mayo Clinic Proceedings, he blames our widening waistlines on the dramatic decline in daily energy expenditure that has resulted from increased mechanization on the job, labor-saving devices at home and changing cultural practices such as online shopping, drive-up windows and "cocooning" with videos and mega-channel TV.
"Most people don't realize how very sedentary our lives have become," Blair says. "But if we burn even 100 fewer calories each day, that's the energy equivalent of 10 pounds of fat in a year."
Blair contends that America's diet and leisure-time exercise habits have changed little during the past few decades. Dietary surveys and other data collected by the U.S. Department of Agriculture "[suggest] that energy intake in the United States has not increased during the past 40 years," he writes. Studies of physical activity habits only assess participation in leisure-time sports and fitness activities, says Blair, who adds that these numbers have remained constant over the last 25 years.
America's alarming girth growth, say Blair and numerous other health experts, is directly related to "physical activity being engineered out of daily life." In our computerized, remote-control culture--in which moving walkways whisk travelers through airports and doors fly open as if by magic--Blair says the average adult expends about 300 to 700 fewer calories per day than our parents did. Although numerous studies have demonstrated that lifestyle activities, such as climbing stairs and parking in the farthest space, can provide health benefits similar to those gained in a gym workout, Blair says our society has created a "toxic environment" that discourages movement. Streets are often too dangerous for pedestrians to cross, stairwells are frequently hidden, and parks in some areas are unsafe.
"Obesity is an environmental issue," says John Foreyt, director of the behavioral medicine research center at Baylor College of Medicine in Houston. "Westernized nations have unlimited access to good-tasting, calorically dense foods and very little energy expenditure during a typical day. This 'obesogenic' environment is completely opposite to the one that shaped human evolution." Our ancestors evolved effective mechanisms to store fat in case of famine, he says, which may now make us less able to shed fat in times of plenty.
Although Foreyt agrees that Americans expend about 300 fewer calories per day than previous generations, he disagrees with Blair's assertion that food consumption has remained steady. "Studies show we're eating up to 200 calories more per day than we did just 10 years ago," Foreyt says. If current trends continue, he estimates that everyone in America will be obese by 2230.
Foreyt and Blair are among a growing number of health experts calling for public health initiatives to help Americans meet the U.S. surgeon general's recommendation to accumulate 30 minutes of moderate activity on most days. "Restoring physical activity into our daily routine represents a critical goal," says pediatrician William Dietz, director of the division of nutrition and physical activity at the federal Centers for Disease Control and Prevention in Atlanta. "This may involve changes as mundane as improving the location and appearance of stairwells or as complex as the redesign of communities."