Brisk walk is a good place to start

Happy couple walking along road together

If every adult in the world stepped together onto a giant scale, our combined weight would be approximately 287 million tons, according to a study published last year. That’s about 15 million tons heavier than what researchers say is a healthy number.

The world is fat, and getting fatter. Nowhere is that more obvious than in the United States where American adults account for 5 percent of the global population and one-third of its excess weight.

Our ongoing fight against fat tends to focus on how and what we eat, but Jim Sallis and Bess Marcus, professors of family and preventive medicine at the University of California San Diego School of Medicine, say physical inactivity presents an equally sizable problem.

Sallis and Marcus were co-authors for a series of papers published in the British journal The Lancet last year that described some of the most worrisome aspects of global inactivity, and its deleterious effects upon health and social well-being.

Q: For people trying to lose weight, why is physical activity as important as diet?

A: In obesity discussions, physical activity is usually viewed only as a way to burn calories and help reduce risk of obesity. This is too narrow a view. Physical activity has powerful health effects on many common diseases.

Inactivity is, for example, a risk factor for most of the major killers: heart disease, stroke, type 2 diabetes and some cancers. Inactivity causes 9 percent of premature deaths in the world, more than 5 million deaths per year. Worldwide, about 31 percent of adults are not meeting the 30 minutes per day guideline for physical activity, and inactivity rates in the Americas are among the highest in the world, about 43 percent. Physical inactivity is a more common risk factor for ill health than smoking. The Lancet authors concluded it is one of the most serious threats to health in the world.

Q: In the United States, we’ve been inundated for decades with messages to exercise more and more often. How have we responded?

A: It’s hard to argue that Americans have active lifestyles. We drive almost everywhere. Most jobs are in front of computers, with little heavy lifting. The average adult watches four hours of TV a day, plus time surfing the Internet and on Facebook. Labor-saving devices do much of our housework. Children’s lifestyles mirror these inactive patterns: They sit in school. They play computer games. Time for PE and recess in schools is declining.

In short, all of the ways that our ancestors were active have been systematically eliminated by technology. The obesity pandemic hasn’t overlooked perfect-weather San Diego. Only about 14 percent of San Diego adults report no leisure time physical activity, which is encouraging, but just 20 percent say they participate in any vigorous activity.

Q: What’s the remedy?

A: Certainly we would like more people to commit to being active, but given how our environments are set up, most people have trouble meeting their goals. We need to rethink how we organize our daily lives and build our cities. It’s now recognized that walking for transportation has declined, in large part because cities are designed so that most everyone must drive from home to work, to shopping and to school. Roads are designed so cars can drive fast, but this makes walking unpleasant and dangerous. Many neighborhoods lack parks, trails and sidewalks that could make it easier for people to be active for recreation and transport purposes. Living in neighborhoods designed well and designed poorly for physical activity seems to make a big difference for activity, but also for risk of obesity. Our studies have similar findings for children, adults and older adults.


