2.6. Statistical Analysis
The sample size calculation was based on the ‘double-sided two-sample analysis with continuity correction’ (SISA, Simple Interactive Statistical Analysis) method. Assumptions made for this calculation were based on previous nutrition studies [Intention-to-treat (ITT) analyses were performed. Missing values (due to discontinued allocated intervention) were imputed by the ‘last observation carried forward’ (LOCF) principle. Non-normally distributed data were analysed by Mann–Whitney test for between-group comparisons and by Wilcoxon signed rank test for within-group comparisons. Differences in changes after 3 months between both groups were analysed using ANCOVA with adjustment for baseline values. Normality was visually and analytically confirmed by using histogram graphs and applying the Shapiro–Wilk test. Chi-square test was used to analyse dichotomous variables. All statistical tests were two sided, and the level of significance was set at α = 0.05. All analyses were performed using SPSS 22.0 (SPSS Inc., Chicago, IL, USA) and GraphPad Prism 6.04 (GraphPad Software, San Diego, CA, USA).