Especially in the fast fashion segment of the global clothing industry, ill-fitting garments degenerate into waste as they return to store, are left unsold or unused, or otherwise outdate. To address these problems of ill-fit, we accessed from databanks the 3D morphological measurements of 478 French female consumers. We extracted virtual mannequins representative of three dominant bodylines types. Clinical evidence suggests that, among body lines for good fit between a particular consumer and a particular grade of garment, the neck and armholes are pivotal. Cross-tabulating across the above matrix of design requirements, our simulation reveals how virtual fitting for draping and ease allowance on a particular virtual mannequin improves fit and thus reduces garment waste. Given that 3D parametrization holds promise to improve sustainability in fast fashion, we call for clinical trials, as well as for replication or trials in other segments of the fashion industry, other products than garments, and/or other industries.