Objective: Our objective was to examine the stability of body habitus over 15 years in Boston area adult males enrolled in the Normative Aging Study (NAS) and to examine stability as a function of initial leanness or obesity, age and reported body habitus at age 18.
Design: Prospective observational study of anthropometric/clinical measures initiated in 1961-1970, follow-up examinations at regular three and five year intervals. Subjects with complete data at entry, 5, 10 and 15 years.
Subjects: The 2280 Boston area subjects were aged 21-80 years (mean = 42 y) at entry. A subset (n = 350) with complete data for weight (WT) and height (HT) at four points over 15 years provided estimates of body habitus continuity. The prevalence of obesity and age of those studied were comparable to the complete sample of enrolled men (n = 1403) with any missing follow-up measures.
Measurements: Obesity was defined as body mass index (BMI) (weight in kg/height in m2) > or = 27.8 and leanness as BMI < 24.0. Three age categories at baseline (young = 25-39 y; middle = 40-49 y and old = 50-74 y) were used to examine secular and longitudinal changes. Obesity prevalence rates during late adolescence, based on self-reported weights at age 18, were compared with measured prevalence rates at entry and follow-up. Individual changes in BMI over time for each subject were estimated by linear regression and were combined to measure change in age and BMI groups.
Results: Weights and BMI at entry were highly correlated with 18 year values and 15 year follow-up values. New cases of obesity, defined on the basis of BMI, increased over time while the numbers of subjects classified as lean and intermediate decreased. Among oldest subjects both the lean and obese had slight but significant decreases in mean BMI. Among the lean, only the young showed consistent increments.
Discussion: Our results suggest consistency in body habitus among young and middle-aged obese subjects. There was little evidence of long-term reduction. In agreement with previous observations, the current findings of long-term duration in obesity suggest that preventive efforts should be focused on early years.