stackcanary

Hi, I've been looking at material all day and am still confused about multiple testing. For the assignment, we're given a paper where three groups (2 experimental, 1 control), are put on controlled diets, have have biomarkers and memory assessed after 3 months. The question is why it was appropriate for the authors to no correct for multiple testing. They performed post-hoc t-tests for differences before and after the intervention. Most of the documents I've been able to find say that multiple testing correction is used when you're comparing a massive number of metrics and need to make your significance more stringent to keep out false positive results, but those are mostly in relation to gene studies. If there are about 18 metrics being compared between 3 groups (or, each of the two experimental groups to the control group), would they not correct because the number of metrics is relatively low, or would they not compare because the number of groups is low? I'm pretty confused and would love some guidance on this. Thanks!