Longitudinal changes in BMI and in an index estimating excess lipids among white and black adults in the United States

Background: Adult obesity prevalence is influenced by rates of weight gain or loss among individual persons, but few studies have measured individual weight change in large populations. Changes in weight may not coincide with changes in the lipid accumulation product (LAP), a continuous index derived from waist circumference and triglycerides concentration for estimating excess lipids. Design and measurements: Descriptive report of longitudinal changes from US studies that included body mass index (BMI, kg/m(2)) and LAP. Subjects: A total of 16 763 white and black adults studied between 1989 and 1996 in three observational cohorts (Coronary Artery Risk Development in Young Adults, Atherosclerosis Risk in Communities Study and Cardiovascular Health Study). Results: The means of individual annual changes in BMI were positive for young adults, but the mean changes were reduced at older ages (P for linear trend < 0.001), becoming negative after 73-83 years old. These mean, individual changes in BMI, specific to sex and age, were approximately 0.1 U/year greater than those reported from previous, representative, longitudinal measurements collected in the United States between 1971 and 1984. Mean, individual annual changes in LAP were strongly positive before middle age. For men, the annual LAP changes were reduced at older ages (P linear trend < 0.05). For women, they were greater at older ages (white women, P < 0.001) or remained unchanged (black women, P > 0.3). With increasing age, there was a greater proportion of persons whose positive LAP change was accompanied by simultaneous BMI change that was negative or zero. Conclusions: These longitudinal observations made during 1989-1996 suggest greater annual changes in BMI compared to an adult cohort studied during 1971-1984. As estimated by LAP, adults of all ages tended to accumulate excess lipids, including circumstances in which they lost weight.