Forget the slogan “No pain, no gain.” According to Duke University researchers, those who exercise moderately may reap as much gain as extreme fitness buffs. They studied 133 overweight and inactive men and women at risk for heart disease. Those who walked 12 miles per week showed improvements in cardiovascular fitness—including levels of oxygen consumption as great as those who jogged 12 miles a week. The walkers didn’t lose much weight, but they lowered their risk of heart disease. So just do it.