Objective: This study tested the efficacy of an 8-week culturally targeted nutrition and physical activity intervention on body composition.
Methods: A randomized, attention-controlled, two-group trial was conducted in a blackowned commercial gym with a sample of 366 predominantly healthy, obese African American women. A free 1-year membership to the study site gym was provided to participants in both groups. Data were collected at baseline, 2, 6, and 12 months.
Results: Sample retention at 1 year was 71%. Between-group longitudinal analysis including only participants with complete data revealed a trend toward weight stability in the intervention group at 2 months compared with controls (+0.05 kg/m2, p = 0.75; +0.32 kg/m2, p = 0.08, respectively), disappearing at 12 months (+1.37 kg/m2, p = 0.0001; +1.02 kg/m2, p = 0.001, respectively). Within-group analysis demonstrated that intervention and control participants’ fitness (1-mile run-walk) improved by 1.9 minutes (p = 0.0001) and 2.3 minutes (p = 0.0001), respectively, at 12 months. Mixed model regression analyses demonstrated a significant main effect of the intervention on fitness (p = 0.0185) and a marginally significant effect on body mass index (BMI) (p = 0.057), at 2 months, disappearing by 6 months. By 12 months, however, the controls exhibited a significant advantage in waist circumference stability compared with intervention participants (+1.1 cm, p = 0.2763; +2.1 cm, p = 0.0002, respectively).
Conclusions: The intervention produced modest short-term improvements in body composition, but the economic incentive of a free 1-year gym membership provided to all participants was a more potent intervention than the education and social support intervention tested. However, longer-term fitness enhancement remains elusive and demands research and policy attention. These findings have policy implications in that employer-/insurer-subsidized gym memberships may require interventions targeting other levels of change (e.g., physical or social/environmental) to foster sustainable fitness improvements.
