OBJECTIVES: This research quantifies the impact of achieving select population health improvements on disease prevalence and healthcare use. Such information can help inform how population health policies and practices might affect future patient outcomes and health system needs. METHODS:   Using a previously published Markov-based microsimulation approach, we modeled a hypothetical scenario of sustained 5% body weight loss for overweight and obese adults; improved blood pressure, cholesterol, and blood glucose levels for adults with elevated levels; and smoking cessation. Published clinical trials and observational studies informed model parameters and achievable clinical improvements. Relationships between patient characteristics and healthcare use came from Poisson and logistic regression analysis estimated from the 2010-2014 Medical Expenditure Panel Survey and 2014 Nationwide Inpatient Sample. A nationally representative adult sample from the 2013-2014 National Health and Nutrition Examination Survey was extrapolated to national totals using Census Bureau population projections. RESULTS:   Cumulative between 2015 and 2030, achieving these lifestyle and clinical goals results in 9.6 million fewer people with heart disease, 3.3 million fewer strokes, 2.4 million fewer heart attacks, and reduced incidence of cancer and other diseases. Per capita inpatient days, emergency visits, and ambulatory care declines. Reduced mortality suggests an additional 6.3 million adults alive in 2030. Cumulative over the first three years, national inpatient days decline by 4.3 million days and emergency visits by 3.4 million. By 2030, annual inpatient days are 6 million higher and emergency visits 1.7 million higher. By 2030 an additional 16,400 physicians would be required to support the extra 6.3 million people. CONCLUSIONS:   The long term implications of achieving the modeled population health outcomes is reduced morbidity and mortality, but increased use of healthcare services to support a larger population. Health system planning should reflect that improved population health causes short term reductions in demand for healthcare services but long term demand will rise.