Doctors, social agencies and community groups that have long been frustrated by the inability to alleviate environmental conditions that contribute to ailments like heart disease and obesity are promoting the idea that a shift in land-use planning and design can stanch some of the harmful influences. The concept is being put to one of its earliest and biggest tests in the La Alma/Lincoln Park neighborhood near downtown Denver. That's where the city's housing authority used a relatively new decision-making tool known as a health impact assessment to draft a redevelopment plan that encourages physical activity and environmental sustainability.