The objective of this study was to determine the distribution of and trends in obesity in adult West African populations. Between February and March 2007, a comprehensive literature search was conducted using four electronic databases. Journal hand searches, citations and bibliographic snowballing of relevant articles were also undertaken. To be included, studies had to be population-based, use well-defined criteria for measuring obesity, present data that allowed calculation of the prevalence of obesity and sample adult participants. Studies retrieved were critically appraised. Meta-analysis was performed using the DerSimonian-Laird random effect model. Twenty-eight studies were included. Thirteen studies were conducted in urban settings, 13 in mixed urban/rural and one in rural setting. Mean body mass index ranged from 20.1 to 27.0 kg(2). Prevalence of obesity in West Africa was estimated at 10.0% (95% CI, 6.0-15.0). Women were more likely to be obese than men, odds ratios 3.16 (95% CI, 2.51-3.98) and 4.79 (95% CI, 3.30-6.95) in urban and rural areas respectively. Urban residents were more likely to be obese than rural residents, odds ratio 2.70 (95% CI, 1.76-4.15). Time trend analyses indicated that prevalence of obesity in urban West Africa more than doubled (114%) over 15 years, accounted for almost entirely in women. Urban residents and women have particularly high risk of overweight/obesity and obesity is rising fast in women. Policymakers, politicians and health promotion experts must urgently help communities control the spread of obesity in West Africa.