Currently over 30% of American adults are obese, more than twice the percentage prevalent in 1980 (American Obesity Association). At the same time, almost 65% adult Americans are said to be overweight. Such high prevalence levels are a major public health concern. Both overweight and obesity are associated with increased health risk for chronic diseases such as heart disease, type 2 diabetes, high blood pressure, stroke, fatty liver disease and some forms of cancer. In this paper we explore the factors that contribute to increasing rates of obesity and overweight, and study the differences in years 1996 and 2002. We use a multilevel econometric approach to model the four classifications of body mass index (BMI) obese, overweight, healthy and underweight - as a function of individual characteristics, lifestyle indicators and external environment. The results are reasonably consistent within the two years and with findings from previous studies. However, three significant differences are found between the two years at the state-level. Two of them are completely new findings. Higher urban residency is associated with lower rates of overweight and obesity. On the other hand, higher participation in food-stamp programs in the more recent year is associated with increasing prevalence of obesity. Excise tax on cigarettes also has a positive association with obesity only. Previous studies have uses either per-capita sales of restaurants, or price of meals available in fast-food and full-service restaurants. We explored a new variable density of fast-food and full-service restaurants serving meals over a wide price range. Such a variable is used to not only capture the importance of difference between fast-food restaurants and full-service restaurants, but to also distinguish between the effects of lower-priced and higher-priced meals. We find that lower-priced food from fast-food restaurants has positive effect, and higher-priced food from full-service restaurants has negative effect. Three new individual-level lifestyle predictors have been added, and they all seem to be significant in explaining the weight outcomes. Inadequate consumption of fruits and vegetables, irregular or no exercise, and poor self-reported health status are all significantly associated with increasing rates of overweight and obesity.