Approximately one-fourth of chronic disease mortality (e.g., diabetes and heart disease) is linked to a sedentary lifestyle.¹ In 2000, it was estimated that physical inactivity cost the United States $76.6 billion in medical expenses alone.² In contrast, a physically active lifestyle is associated with multiple health benefits, including improvements in obesity, coronary artery disease, hypertension, and all-cause mortality.^3–6 Regular physical activity may be especially important for individuals at high risk for developing type 2 diabetes; a 2000 calorie/week increase in energy expenditure is associated with a 24% reduction in the risk of developing the disease.⁷

Despite the clear benefits of an active lifestyle, > 60% of U.S. adults do not get enough physical activity, and at least 25% are completely inactive during their leisure time.⁸ Technological advancements and changes in the work environment during the past several decades have contributed to a gradual decline in the need for daily physical activity.^9,10 Because of this, many practitioners now recommend a lifestyle approach to physical activity, through which sedentary individuals are encouraged to build more physical activity into their daily routine and leisure time.^8,11

An increasingly popular tool that can support lifestyle physical activities is the pedometer. Pedometer-based interventions have produced significant improvements in physical activity, weight management, blood pressure, and lipid profiles.^11–14 They have also been effective for increasing walking and improving glucose tolerance or insulin sensitivity among participants with type 2 diabetes.^15–19

To date, however, most pedometer studies have had limited external validity because of small or narrowly defined at-risk samples. It is unclear how well a large-scale, commercially available pedometer-based walking program performs in the real world. The purpose of this evaluation was to examine whether an online program titled …