Regional Body Composition Changes with Weight Loss

Abstract

PURPOSE: To examine regional body composition changes with weight loss and the effects of age, gender, ethnicity, initial total body fat % (TBF%), and rate of change in TBF% on these changes. METHODS: Participants were 723 men (M) and 1,802 women (W) 20-74 yrs of age who participated in a 12-wk, 3 days/wk instructor-led exercise and weight loss program which included pre- and post- DXA scans. After completing one 12-wk session, participants could continue and receive a DXA scan at the end of each subsequent session. The mean time between the first and last scan was 1.2 yrs (range = 10 wks to 5.4 yrs). A series of latent growth curve models were used to assess TBF% and android (An), arms (A), gynoid (G), legs (L), and trunk (Tr) fat % (F%) change over time and the effects of age, ethnicity, gender, initial TBF%, and change in TBF%. The level of significance was set at p < .05. RESULTS: Unrestricted models, without any co-variates, showed that TBF% and F% for each region had a significant rate of decrease and that this rate of decrease slowed over time (quadratic slope). The initial F%, F% rate of change per month and F% quadratic slope were as follows: TBF% (35.8, -0.226, 0.004), AF% (34.3, -0.170, 0.004), AnF% (40.1, -0.350, 0.007), GF% (38.9, -0.217, 0.004), LF% (35.5, -0.180, 0.003), and TrF% (38.1, -0.287, 0.006). At baseline, when controlling for initial TBF%: 1) M had significantly lower TBF% (37.4 vs 31.3), F% in the A (36.4 vs 28.8), G (40.5 vs 34.5), and L (37.5 vs 30.3) regions, but higher F% in An (37.0 vs 46.1) and Tr (36.0 vs 41.7) regions than W; 2) older individuals had higher TBF%, but lower F% in the G and L regions; and 3) Whites had more AF% than Blacks, but less An, A, and Tr F% than Asians (AS). The mean change in TBF% was greater in M than W (-4.73 vs -5.69%). In examining rate of change while controlling for initial TBF%: 1) M lost at a faster rate for TBF%, AnF%, GF%, LF%, and TrF% than W; 2) AS lost at a faster rate for TBF%, AnF%, GF%, and TrF%; and 3) older individuals lost at a faster rate for LF%, but a slower rate for GF%. However, when controlling for simultaneous rate of change in TBF% the only slope differences were that M lost LF% faster and TrF% slower than W. CONCLUSION: When controlling for rate of change in TBF%, regional rate of change was not affected by age or ethnicity and the only gender differences were that M lost faster in the L and slower in the Tr than W.