Focusing on the contrast between groups, for a comparison of two independent binomial proportions (those with high fibre AND low meat intake vs other) using Pearson's Chi-square statistic with a Chi-square approximation with a two-sided significance level of 0.05 (P<0.05), a total sample size of 318 assuming an allocation ratio of 1 to 2 has an approximate power of 0.924 (i.e. >90% statistical power) when the proportions responding are 60% and 40%, respectively.