Statistical analyses
The study was powered to detect a significant difference in weight loss at
2 mo among the five groups with a significant trend in weight loss demonstrating
a decrease in percent body weight incrementally going from the omni, semi-veg,
pesco-veg, veg, through the vegan group. Assuming a mean incremental difference
in change in body weight of 1% successively between each of the five groups
(corresponding to an effect size of 0.57), a pooled SD of 2.5%, and significance at a
¼ 0.05, a sample size of 60 participants (12 per group) was estimated to provide
94% power for the linear trend among the five groups [21]. The sample size of 12
per group provided 80% power for differences of 2.85% for linear contrasts
between two groups. Attrition was defined as a participant not completing the
main outcome of body weight at either 2 mo (for 2-mo outcomes) or 6 mo (for
6-mo outcomes).