Studies have reported that newly-arrived immigrants to the US often have better health outcomes, including lower body mass index (BMI) than established ones. This study tests the hypothesis about variation in initial BMI among immigrants who have come to the US during different time periods. Using 1989-2011 data from NHIS, we found that recent immigrants in general were larger at their time of arrival than the earlier ones. However, we also observed variations in initial BMI across racial and ethnic origin groups. For example, we found the trends for Hispanic and Asian immigrants to have increased during the study period. The average initial BMI for recent Hispanic immigrant cohorts surpassed the upper limit for normal weight. While earlier cohorts of Asian immigrants had much lower initial BMI than other immigrant groups, the estimated annual increase among Asians was the most rapid. Our findings support the observation about the rising body weight and obesity rates worldwide. The policy implications of our findings were also discussed.