TITLE: Increased Fruit and Vegetable Intake Has No Discernible Effect on Weight Loss: A Systematic Review and Meta-analysis

AUTHORS/INSTITUTIONS: K.A. Kaiser, A.W. Brown, M.M. Bohan Brown, J.M. Shikany, R.D. Mattes, D.B. Allison

MEETING: Obesity Week 2013

KEYWORDS: Diet, Energy metabolism, Public Health.

ABSTRACT:
Background: A common dietary recommendation for weight loss is to eat more fruits and vegetables (F/V). Without a compensatory reduction in the intake of total energy, significant weight loss would be unlikely. Our objective was to synthesize the best available evidence on the effectiveness of being assigned to eat more F/V for weight loss or prevention of weight gain.
Methods: We searched multiple databases for randomized controlled trials (RCTs) where the singular effect of F/V intake was evaluated for effects on body weight/composition. Inclusion criteria: N per arm ≥ 15; duration of intervention ≥ 8 weeks; stated primary or secondary outcome variable is body weight/composition; stated goal of the intervention is weight/fat loss or prevention of weight/fat gain; intervention includes a variety of F/V that remain minimally processed; and was published prior to August 1, 2012.
Results: Five RCTs met all criteria, but only three reported usable weight data; seven other RCTs met all criteria except for having weight as a primary outcome, but only three reported usable weight data. Preliminary analysis indicates a standardized effect (positive estimates indicate increased weight as a result of F/V consumption) for RCTs meeting all criteria was -0.24 (95% CI -0.56 to 0.08), p = 0.14. The standardized effect of increased F/V intake on body weight for RCTs meeting all/most criteria was -0.02 (95% CI -0.14 to 0.11), p = 0.80. The six RCTs for which weight data was unusable for meta-analysis all reported non-significant differences between treatment and control groups for weight/body composition outcomes.
Conclusions: Based on present evidence, recommending increased F/V consumption to treat or prevent obesity without explicitly combining with efforts to reduce intake of other energy sources is unwarranted.