The purpose of this study is to promote weight loss among those who are overweight and obese, and prevent weight gain among those of normal weight through an environmental intervention targeted to all employees at six hospitals in central Massachusetts. The hospitals will be matched according to size, and within each matched pair randomly assigned to either the intervention or control group. The intervention will promote active living, in which physical activity is incorporated into each participants' daily routine. Participants will also follow a healthy diet, characterized by higher intakes of fruits, vegetables, fish, poultry, legumes, and whole grains. Participants will consume less high fat foods and refined grains, and reduce their total caloric intake through smaller portion sizes.