Wednesday was the second annual Start! Walking Day, a campaign developed by the American Heart Association to encourage employers all across the country to provide incentives for their employees to walk at work.

Why is walking at work important?

Walking is a simple exercise that almost anyone can do anywhere.

While walking may not burn calories like more vigorous activities, it adds, leading to big differences in who is lean and who is overweight. Regular walking, as little as 30 minutes per day, also lowers your risk of heart disease, stroke, diabetes, dementia, depression, osteoporosis, arthritis and cancer. It also boosts your immune system and may retard aging.

Dr. James Levine at the Mayo Clinic in Minnesota has done studies showing that the calories people burn during daily nondescript activity is far more powerful in helping people to maintain or lose weight than the time they spend at the gym; he also has helped identify why some people are thin and some are fat.

How did he do this? He and his colleagues devised a clever devise that would measure all movement that a person did during the day. They fitted this device onto two groups of people — one group was thin, the other overweight — and they measured their daily activity.

What they found was that the thin folks moved, on average, 2-1/2 hours more each day than the overweight folks, burning about 350 calories from this movement. The thin group also tended not to gain weight even when overfed; they just moved more.

Exactly what kind of activities did these thin people do? No, they weren't running marathons; they just stood more, walked, fidgeted and used their arms and hands when they talked.

In one of his recent studies published in the journal Diabetes, Levine showed that thin people walked on average 3-1/2 miles per day more than their overweight counterparts; and when both thin and overweight folks were overfed, they all started to walk less. Overeating seemed to increase the tendency to move less, which then increased the risk for weight gain.

It may seem impossible to reach a fitness goal, especially if you are trying to do something gargantuan, like losing 50 to 100 pounds or more. But consider this: An average tortilla or potato chip has about 12 to 14 calories — not much to worry about, right? But, eat one extra potato chip a day for 20 years, and you'll put on 25 to 29 pounds just from that one chip. And, just three minutes of moderately brisk walking a day (at 3 mph) will burn off those 13 calories.

Can you become one of those restless, fidgety people who naturally burn calories? You may not be genetically programmed to do that, but by putting yourself into environments that encourage more physical activity, you will cultivate your own capacity to move.

So, why not start a walking program where you work? Call your Heart Association office at (916) 446-6505 for a Start! Walking Day tool kit.

Drs. Kay Judge and Maxine Barish-Wreden are medical directors of Sutter Downtown Integrative Medicine program in Sacramento, Calif.