Changes in body mass index among Tongan adults in urban and rural areas between the 1970s and 2000s

The purpose of this study was to determine trends in body physique among Tongan adults, between the late 1970s and the 2000s. Two areas were studied: Kolofo'ou town (as an urban area) and 'Uiha village (as a rural area). Measurements of body weight and height were taken 4 times for all residents in both areas in 1977/79, 1983, 1990, and 2001. The number of the subjects in 1977/1979, 1983, 1990, 2001 were 130, 138, 102, 71 in the urban area and 92, 89, 90, 66 in the rural area respectively. The mean body mass index (BMI, kg/m(2)) values of males in the rural area increased significantly, from 28.0 kg/m(2) in 1977 to 31.0 kg/m(2) in 2001 (p = 0.001); in females, mean BMI values were 30.6 kg/m(2) in 1977 and 33.3 kg/m(2) in 2001, this change was not statistically significant. However, the BMI values did not significantly change in males or females in the urban area. The proportion of rural males with a BMI >= 30 kg/m(2) had increased from 24.5% in 1977 to 55.5% in 2001 (p = 0.012). Although the mean BMI values for males and females were higher in the urban area than in the rural area until 1990, the differences between the two areas were not observed in 2001, due to an increase of BMI in the rural area. Changes of the mean BMI values in the rural and urban areas studied, between the late 1970s and 2000s, were 10% and 4%, respectively.