The kilt is normally worn above your waist unlike pants and as men tend to have a belly bulge above their waist which usually shrinks most when weight is lost, it is understandable that kilts tend to slacken off more than pants if weight is lost. My experience with new kilts from a variety of manufacturers from super cheap to expensive hand sewn and in acrylic, PV and wool of 10, 13 and 16 oz weights is that all slackened off on the first wearing then remained constant thereafter. Kilts can be a better test than pants belt size for determining whether your weight is changing.

Bill